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Posted by Michael Posner on 3rd April 2015
It’s been a while since Xilinx shipped the first UltraScale VU440 engineering sample devices to Synopsys so I thought it time to deliver a short update on development progress. It might be hard to see in the above but that is a picture of one of the new development HAPS systems for the UltraScale VU440 devices. I say hard to see not only as the picture quality is low but also because we have the system completely configured with intelligent interconnect as part of our stringent characterization and functional validation process.
Each module is individually tested, see picture below as an example, this is the controller module in standalone test. The controller module hosts the HAPS supervisor which controls the system and manages advanced capabilities such as the Universal Multi-Resource Bus, UMRBus for short. Once all individual modules are signed-off they are assembled and the system is validated.
So far both the Xilinx VU440 devices and the new systems are functioning well. Xilinx has posted an errata on the engineering sample VU440 devices but these issues do not preclude the devices from being useful for system development or actual usage as part of a production prototyping project. All IO’s are operational as well as the transceiver GTH links. We have been filling the devices with high speed toggle designs as part of the performance and power characterization and smaller IP designs for other test purposes so we have not compared the utilization between V7 and UltraScale devices yet. We still predict that the UltraScale VU440 devices will deliver ~26 Million ASIC gate capacity, about 2.2X increase over the V7 2000T devices.
As a teaser for future blogs, the new integrated solution is expected to deliver
- Highest performance w/superior partitioning & new time domain pin-multiplexing schemes
- Always available debug with deep trace storage
- Fastest time-to-first-prototype with HAPS aware prototyping software
- Rapid Turn-around Time from RTL to Bit file with incremental flows
- Native integration for regression farm & remote accessibility
- Both HW and SW tool flow is Modular & scalable to over 24 FPGA’s (Over 600 Million ASIC Gate capacity)
- Hybrid Prototyping ready
Preserves existing HAPS investment
- Interoperable with HAPS-70 & HAPS-DX, (mix and match HAPS V7-based systems with UltraScale systems) same form factor, I/O voltages, HT3 connectors, daughter boards, cables
In the coming months I’ll post more information on these new and unique capabilities.
Posted in Admin and General, ASIC Verification, Bug Hunting, Daughter Boards, Debug, DWC IP Prototyping Kits, Early Software Development, FPGA-Based Prototyping, HW/SW Integration, Hybrid Prototyping, In-System Software Validation, IP Validation, Man Hours Savings, Milestones, Project management, Real Time Prototyping, System Validation, UltraScale, Use Modes | Comments Off
Posted by Michael Posner on 20th March 2015
I spent a lot of time this week talking about timing biased automated partitioning which is the ability of the ProtoCompiler partition engine to generate a partition and pin multiplexing implementation with the goal of maximizing performance of the final prototype implementation. As it’s getting close to Easter I thought it was fitting to discuss ProtoCompiler’s Multi-Hop optimization algorithm. (Easter, Easter bunny, hop, you see what I did there?)
Firstly what is a Hop you ask? In the image below you can see the ASIC design example with combinatorial logic between two register points
It’s possible during partitioning for FPGA-based prototyping that these two registers end up in different FPGA’s as seen in the image below.
This is what is known as a single hop. The design has been split up with the starting and ending register points in separate FPGA’s. However, without timing biased capabilities it’s possible that a partition is created that spans multiple FPGA’s. An example of this Multi-Hop is represented in the image below
In our example above FPGA B has basically become a feed through FPGA and while this helps a partition engine get to a partition solution it has a dramatic effect on the overall performance of a prototype platform. To explain the timing impact lets go back to our original ASIC design and review the timing between the register points
In our made up example the combinatorial logic has a timing impact of about 10ns. However in our FPGA partition where you have the critical path split up over multiple FPGA’s timing becomes much more significant. The reason for this is that you typically have to apply pin multiplexing between FPGA’s as you have more signals than you have physical pins (One of the three ASIC Prototyping three laws which are the grounding facts driving this blog) Now if you review the timing impact with a typical pin multiplexing scheme inserted you suddenly see the impact of a Multi-Hop
But not to worry if you are using ProtoCompiler as the partition engine is not only fast but it’s timing biased and includes a Multi-Hop optimization algorithm.
When Multi-Hop optimization is enabled ProtoCompiler partition engine will:
- Focus on reducing the number of multi-hops, with a goal of zero
- If multi-hops are needed to complete the partition the focus turns to reducing the path length of the multi-hop
- Avoids pin-multiplexing on multi-hop path
- If pin-multiplexing is needed the focus turns to using the lowest pin-multiplexing ratio on the multi-hop path
- Selects pin-multiplexing ratio based on timing slack
Knowing that eliminating multi-hops would lead to higher prototype performance you might think that by default the partition engine should not allow any multi-hops. However multi-hops do play a vital role sometimes in enabling an automated partition solution to be found.
ProtoCompiler’s timing biased multi-hop optimization is making a huge impact on the resulting HAPS prototyping performance. Across a suite of over 40 ASIC designs ProtoCompilers timing biased optimizations improved the clock period by an average of 50ns. HUGE improvement in resulting performance. Across this suite of designs, ProtoCompiler reduced the number of nets that are included in multi-hop paths of length two or greater by up to 80%. For most designs in the suite, the number of paths of length three or greater was reduced to ZERO. Also, for most designs in the suite, the pin multiplexing ratio of the multi-hop path nets required to get feasible automated partition was reduced to one (i.e. no pin-multiplexing required). Fantastic. Not only is ProtoCompiler’s partition engine super-fast running in minutes for multi-million ASIC gate design but the out of the box results are phenomenal.
I’m out on vacation for a week (yes even I need time off once in a while) so no blog next week.
Posted in ASIC Verification, FPGA-Based Prototyping, Tips and Traps | Comments Off
Posted by Michael Posner on 16th March 2015
Possibly inspired my one of my blogs, Troy Scott, wrote a new whitepaper to help dispel the myths of physical FPGA-based prototyping. TTFP = Time To First Prototype
I highly recommend this whitepaper as unlike my blogs, which I write mostly on the fly, this whitepaper obviously had a lot of thought put into it.
That’s it for the blog this week. I was traveling in the UK last week so I am a little jet lagged. While there I picked up a little UK history
It’s a ceramic poppy from the Tower of London remembers exhibit. It’s an amazing piece of history and I feel honored to be able to buy one.
I received another honor, this time from the hotel I stayed at
Yes, I am still known as Mr Bacon. This has a little to do with the fact that I love bacon and more so because I always seem to wear a T-Shirt that says BACON on the front of it.
I also had some fun with the rental car while trying to find parking one day. Below you can see my parking spot halfway up a hillside.
I’m not sure if you can see it or not but the back wheel is floating in the air. Fun, fun, fun.
Posted in FPGA-Based Prototyping, FPMM Methods, Humor, Milestones, Project management, Technical, Tips and Traps | Comments Off
Posted by Michael Posner on 20th February 2015
Last week’s blog How many ASIC Gates does it take to fill an FPGA? definitely stirred the pot. Part Deux (two?) goes back to basics filling in some gaps and follows up with data supplied by my good friends over at Xilinx.
So first for clarification, apparently not everyone who reads my blog understands what a Xilinx Logic Cell, LC, is or what a Look Up Table, LUT, is. I was going to create a nice set of slides explaining but thanks again to Xilinx, here is one they prepared earlier. It should be noted that Xilinx provided me with written permission to re-use these as part of my blog. The full (PUBLIC) Xilinx presentation can be found here: http://www.xilinx.com/training/downloads/what-is-the-difference-between-an-fpga-and-an-asic.pptx
The Xilinx Logic Cell basics, a cell including combinatorial logic, arithmetic logic and a register. Your RTL source code is “mapped” into these Logic Cells.
A Logic Cell is the basic building block within the Xilinx devices and there is a *lot* of these per device, 4.4 Million in the new Xilinx Virtex UltraScale VU440. Yes that’s right, they are very, very, very small.
Part of the Logic Cell is a Look Up Table which is used to implement combinatorial logic.
My contact over at Xilinx also provided me the Xilinx used standard calculation of equivalent ASIC gates of the Xilinx devices.
–//– From Xilinx
Here are the basic principles that we’ve tried to stick to when generating ASIC gate count numbers:
- – 6 to 24 gates per LUT (depending on the number of inputs used)
- – RAM bits are equivalent
- – Up to 100 ASIC gates per I/O;
- – 7 gates per register
So for the VU440 here’s how this shakes down:
- Minimum 6 x 2,532,960 LUTs = 15,197,760
- Maximum 24 x 2,532,960 LUTs = 60, 791, 040 ASIC gates
IOs : 100 x 1456 = 145600 ASIC gates
Registers : 7 x 5.065,920 = 35,461,440 ASIC gates
So by this math we could have claimed anywhere from 50,804,800 to 96,398,080 ASIC gate equivalent in the VU440.
–//– End From Xilinx
So great, this passes what I call the basic “Stupid” test, as in there is sound logic and defendable data behind the calculation. It also highlights the large variance in “gate counts” which is significantly influenced by the number of inputs used as part of the look up table calculation. It’s exactly as I stated in last week’s blog, the conversion from ASIC gates to FPGA ASIC gate equivalent is design specific. Some designs will map well, some not so much.
In the material that Xilinx supplied I also spotted this slide which reinforces this point.
Specifically for Prototypers, the conclusion is very important. The Prototypers goal is to NOT modify the golden RTL source for prototyping otherwise you will not be validating a true representation of the design. Yes, some modifications are needed such as RAM’s, gated clock conversion but these can be verified as identical and are an acceptable trade-off. Outside of this the RTL is not customized for FPGA meaning that many of the dedicated resources cannot be directly mapped to. This leads to inefficient mapping of the RTL code to FPGA and is why a “fudge” factor is required in the ASIC gate equivalent calculations. The restriction is typically the Look Up Tables for combinatorial logic mapping, you run out of those before anything else. (not all the time but most of the time). By being conservative in the ASIC gate count capacity claims the vendor can ensure that expectations are met for a majority of designs
Posted in ASIC Verification, FPGA-Based Prototyping, Man Hours Savings, Milestones, Use Modes | Comments Off
Posted by Michael Posner on 30th January 2015
I was forwarded this user quote and I thought I would share as it was so heartwarming for me
The design came up on HAPS in less than two weeks and we found a rather serious bug early in testing. This is the bug that would have cost the company dearly if it wasn’t found until later in the development cycle.
It’s short and sweet and communicates the HUGE value that FPGA-Based Prototyping delivers. This note reminded me that a while back I did an internal analysis of the value of HAPS FPGA-based prototyping in respect to the various use modes. The use modes I examined was Functional Verification, HW/SW Integration, Firmware Development, System Validation and Software Development. First I created a baseline score for HAPS in respect to various user requirements. This list stays consistent across all use modes.
- Early Availability
- Initial Design Setup
- Iteration Turnaround Time
- Execution Speed
- Deployment (Ease of/Cost of)
- HW Debug Visibility
- SW Debug Visibility
How the scoring works, 1 = Sub-Optimal, 10 = Excels. To score I created a set of definitions per requirement and using real data which compared the results to other technologies thus to objectively score. The scores are mapped into a radar chart. Here is the scoring baseline for HAPS. I should point out that its subjective but I tried to be as data driven as possible. If anything I might have been a little harsh on HAPS to be fair.
At the same time and using the same list of requirements I scored the NEEDS of the use mode. For example the user needs for software development are pictured here. Note the dotted line.
The baseline needs were mapped for each of the desired use mode. Then it’s a simple case of overlaying the results of the baseline value score of HAPS against the use mode. It’s a multiplication of the value times the need. This way it clearly shows where there is synergy of a need and as strength.
Starting with Functional Verification
Remember the dotted line represents the user needs within the use mode of functional verification and the solid line represents the relative strengths of HAPS. Within a radar chart it’s easy to see the matching requirements and HAPS strengths. It’s clear to see that while HAPS does bring value to functional verification it’s definitely not the best technology for the use case. Hey, we all knew this already. A simulator such as VCS or emulator such as ZeBu is a far better choice for functional verification as they deliver on the key needs of the use case such as early availability, debug visibility, capacity etc. But I also know that HAPS is used in this use mode as the performance enables a huge amount of tests to be run in a short amount of time flushing out those hard to find RTL bugs.
Now lets review the HW/SW Integration use mode
Immediately it’s clear that the value of HAPS FPGA-based prototyping is far better matched to the requirements for HW/SW Integration. HW/SW Integration is typically the point at which FPGA-based prototyping is deployed in development. As more and more RTL blocks are coming together and the volume of software has become significant then the additional performance that HAPS FPGA-based prototyping delivers is needed to execute in a reasonable timeframe.
Now onto Firmware Development
FPGA-based prototyping enables the use of real physical interfaces using the real interface blocks such as DesignWare IP. This means that the hardware aware firmware development is a key use case for HAPS FPGA-Based prototyping and this is represented in how well the values match the use case needs. The real physical IO, actual RTL blocks combined with the high performance operation make HAPS FPGA-based prototypes one of the best firmware development platforms next to the real silicon. Actually I would be bold enough to say better than the real silicon as once you have silicon its too late to fix RTL bugs!
For the same reasons as firmware development it’s clear to see that HAPS FPGA-Based prototyping is the best technology to address the needs of System Validation use mode. In System validation you will be running lots of software against the hardware, doing interoperability and compliance testing against real hardware. No other technology enables you to do this, PRE-SILICON
Finally the software development use mode
This is the traditional and most well know use mode for FPGA-based prototyping. Again the HAPS values map very well against the needs and requirements of Software Development. Really the only area in question is capacity. I thought it would be interesting to add the benefits of Hybrid Prototyping into the scoring for this particular use model.
Hybrid Prototyping, the combination of HAPS FPGA-based and Virtualizer Virtual Prototyping makes for a powerful platform for software development. Hybrid Prototyping combines the accuracy, performance and real world IO of HAPS with the capacity and differentiated debug capabilities of Virtualizer. I can tell you that a number of customers have adopted Hybrid Prototyping to improve their early software development activities. A number of these have been able to accelerate their software development and validation to a point where the software run on the real silicon on day one! Hey bonus, the green radar chart line looks like a fish, do you see it?
Anyway, there you go, the value of HAPS across multiple use modes. Is this consistent with your scoring of FPGA-based prototyping in respect to your project usage?
Posted in ASIC Verification, FPGA-Based Prototyping, HW/SW Integration, Hybrid Prototyping, In-System Software Validation, IP Validation, Milestones, Project management, Real Time Prototyping, System Validation, Use Modes | 2 Comments »
Posted by Michael Posner on 25th January 2015
Last week I spent a week in Japan visiting users to discuss their FPGA-based prototyping challenges and explain how Synopsys can help. My overall take-away of the visits was that many companies want to expand their current single FPGA-based prototyping to multi-FPGA but fear the challenges associated with this. The summary of what I explained was pretty simple but to the point. #1 Having a defined methodology, flow and tool set is key. #2 Yes Multi-FPGA is more complex but it’s not as steep of a learning curve as you may think. And that’s it…..
#1 Having a defined methodology, flow and tool set is key
In respect to methodology you of course can refer to the FPGA-based Prototyping Methodology Manual, FPMM. (English and Japanese versions, 英語版と日本語版) I used Google translate so I hope I didn’t just offend the whole of Japan. Read the FPMM and you will become an expert prototyper but we all know that in this age of technology a summary is always nice. This is why I blogged about 3 Phase Approach to Successful Prototyping a while back. Yes, this is the blog with the upside down pyramid which at the time I thought was a great way to show the progression down through a funnel. The three phases are “Make Design FPGA Ready”, this is all about making the ASIC RTL FPGA friendly. “Bring Up Functional Prototype”, this is where you want to get onto the hardware as quickly as possible so you can functionally validate the design. Finally “Optimize Prototyping Performance”, pretty self-explanatory really.
Along with a defined methodology you need to utilize a tool flow which is designed for prototyping. I was amazed in Japan that many companies still tried to use the FPGA vendor tools for prototyping. I have nothing against FPGA vendor tools, they are great for their job which is FPGA synthesis. When I asked about the challenges these customer faced it was the same story I have heard before, ASIC clock conversion, gated clocks, memories and for the few that did multi-FPGA the key challenge was clock/reset synchronization and pin multiplexing. If you want to go fast on the freeway you don’t buy a bicycle you buy a car, it’s the same with prototyping. If you want to prototype buy a tool set which is designed for the purpose. I blogged about ASIC Gated clock conversion a while back, Unlocking the Secrets of ASIC Clock Conversion, which is just one example of a tool set designed for prototyping. Search my blog and you will find a stack more examples of what is possible by the tools these days. You need a tool set which is more than just a FPGA synthesis tool, you need a tool set that understands your challenges and can help with automation and dedicated capabilities.
#2 Yes Multi-FPGA is more complex but it’s not as steep of a learning curve as you may think.
If you have never prototyped before I’m not going to tell you to start doing multi-FPGA prototyping straight away, too many variables to take on at once. Start small, create a single FPGA-based prototype of a subsystem of your design. Don’t fall into the trap of thinking you can get away with using the FPGA vendor tools (see above) use a dedicated FPGA-based prototyping tool. This is exactly why we provide ProtoCompiler DX as part of the HAPS-DX system. ProtoCompiler DX is everything you need to implement the prototype and more as it includes high visibility debug capabilities. Once you have a prototype up and running on a single FPGA, then it’s time to expand, but don’t bite off more than you can chew, again start small. My suggestion is that you do not add anything new to the design you already have operational. Simply select a block or two from the existing design and move them into a 2nd FPGA. Using your multi-FPGA prototype tool, such as ProtoCompiler, get familiar with partitioning and pin multiplex IP insertion. Get familiar with customizing the hardware to match the needs of your design. Abstract Partition Flow Advantage, this is an important step to ensure that you create the highest performance multi-FPGA prototype. Once you have the same design up and running on two FPGA’s and a design flow and expertise in place you are ready for greater things. Go off and be successful in multi-FPGA prototyping.
The weather was pretty nice in Japan, here is the view from the hotel I was staying at:
We had lots of nice meals out, can you guess what was served at this restaurant?
We did a day trip to Shin-Osaka via the bullet train, Shinkansen, what a mean looking train
Nice view of Mount Fuji on the way up
While the Japanese can build a train that goes 200 MPH they have the same problem as the rest of the world, horrible coffee. Luckily when we arrived the local team treated me to vending machine coffee
Of course many may question my judgment for even trying train coffee and vending machine coffee. You have to remember I was jet lagged and this was better than no coffee….. but only marginally.
I met the star of the film, Big Hero6, Bay Max, well at least his inflatable body double
The funny thing is that Bay Max the real character is also inflatable so what this really a body double or his clone?
Posted in FPGA-Based Prototyping, FPMM Methods, Getting Started, Technical, Tips and Traps, Use Modes | Comments Off
Posted by Michael Posner on 16th January 2015
In late 2013 I blogged about the newly announced Xilinx UltraScale devices, the VU440 specifically that will be the largest FPGA device on the market: http://blogs.synopsys.com/breakingthethreelaws/2013/12/xilinx-fpga%E2%80%99s-for-fpga-based-prototyping/
Well this week Xilinx officially announced that they have shipped the first samples of the VU440 devices: http://press.xilinx.com/2015-01-15-Xilinx-Delivers-the-Industrys-First-4M-Logic-Cell-Device-Offering-50M-Equivalent-ASIC-Gates-and-4X-More-Capacity-than-Competitive-Alternatives
And check out who received the first of these samples…………………………… ok, you don’t need to read it, Synopsys did…….. We have optimized every generation of our HAPS prototyping systems for the highest system performance, greatest capacity while adding significant capabilities on top delivering prototyping specific features. We all know the FPGA device is a required component within the FPGA-based prototyping hardware but it’s not what defines or makes the solution useful. Anyone can slap an FPGA on a board but this does not help a prototyper as the device alone does not deliver the capabilities they require. Prototypers rely on a solution which includes a software implementation tool flow, integration between hardware and software accelerating time to operation, built in capabilities such as high speed pin multiplexing and high visibility debug to ease bug hunting while being modular and scalable. (side note: Synopsys offers exactly this…. just in case you didn’t know)
I recommend you also check out the VU440 demo video. It stars my friend Kirk from Xilinx who introduces the new device and the demo running ten ARM Cortex-A9 CPU’s, pretty impressive. http://www.xilinx.com/products/silicon-devices/fpga/virtex-ultrascale.html#uniquePlayer1
Over the coming weeks I’m going to focus my blogs on the capabilities that the new Xilinx UltraScale devices deliver and the impact they have to prototypers. As noted above, an FPGA alone does not deliver FPGA-based prototyping so I will discuss how the device capabilities are expected to be integrated and leveraged delivering a solution.
Oh, and just because Synopsys has received Xilinx sample devices don’t expect a new HAPS next week. Delivering a solution requires hardware development, software development and a huge amount of validation. But I’m confident that when you are ready to adopt, Synopsys will be ready to deliver…..
Posted in Admin and General, ASIC Verification, Bug Hunting, Debug, Early Software Development, FPGA-Based Prototyping, HW/SW Integration, In-System Software Validation, Man Hours Savings, Milestones, Technical, Tips and Traps | Comments Off
Posted by Michael Posner on 10th January 2015
Let me be the last to wish you “Happy New Year” and all that….
Of course it was the Consumer Electronics Show, CES recently and no good blogger would let this opportunity pass without writing something about it. Regardless of this I’m still going to write something. (If you got that joke comment below)
Hot at CES was self-drive cars with Advanced Driver Assistance Systems (ADAS), Sling TV, SuperHD TV’s, robots and of course wearables and the Internet of Things, IoT, because everyone wants a cooker with built in internet browser (well I do but as I already have a full PC in the kitchen for streaming TV and web browsing I will hold off on buying a cooker with similar capabilities)
It was nice to see that a number of projects that I know have been prototyped were being debuted at CES. It’s very fulfilling seeing a product go from idea to reality. While the big buzz was around everything you could see it’s the things you could not see which I want to discuss this week. These little electronic gadgets power the world of self-drive cars, wearables and IoT…. Yes I’m talking about sensors!!!!!
Lets face it, the sensors themselves don’t make the product but without them the device would not be able to operate so they really are the little product hero’s. Managing and data acquisition from these sensors can be a complex project in itself which is why Synopsys made it easier with the DesignWare Sensor and Control Subsystem.
This nifty subsystem is optimized to process data from digital and analog sensors, offloading the host processor and enabling more power efficient processing of the sensor data. The DesignWare Sensor and Control IP Subsystem provides designers with a complete, pre-verified solution that optimizes sensor fusion and actuator/motor control functions increasingly prevalent in automotive, mobile, industrial and IoT markets.
If you look at the block diagram above you can see that the interface to these sensors is usually pretty simple, UART, DAC/ADC, SPI, I2C and basic GPIO with the most complex interface being AMBA APB. I worked with a user recently who wanted to incorporate sensor information directly into their FPGA-based Prototype. The solution we came up with was to utilize off-the-shelf Peripheral Module interface, PMOD, boards. PMOD is a standard defined by Digilent Inc : http://en.wikipedia.org/wiki/Pmod_Interface
Diligent have a wide range of these little modules: http://www.digilentinc.com/Products/Catalog.cfm?NavPath=2,401&Cat=9 covering various applications.
Note that the PMOD’s are typically a standard 6-Pin interface with 4 signals, one ground and one power pin so very low pin count. The user connected these to the new HAPS GPIO board, pictured below, in order to interface the modules into their custom design modeled within HAPS.
Note that the HAPS GPIO board is a vertical mounted board so just like the PMOD’s themselves do not take up much physical real estate.
We ended up making full use of the HAPS GPIO board with multiple PMODs connected, interface to the ARM debugger, LED’s to signal various operational states and push switches to simulate user input. The GPIO board is very versatile with 3 standard 3.3V HAPS 10-pin GPIO headers, (Compatible with HAPS BIO1), 2 high-speed VCCO level GPIO headers (Red), 20-pin ARM JTAG header, Micro-USB for UART, MMCX clock connectors, 5V TTL header for serial LCD display, Level shifted header for I2C and SPI, 6 buttons and 4 LEDs on mini-daughter board which is connected to 3.3V HAPS 10-pin GPIO header when needed.
Unfortunately I was sick during the break so I didn’t get to as many of my little projects as I would have liked. I did however manage to complete one of them that I had been excited about for a while now. I made myself a portable gaming station complete with 412 games from the 1980-1990 era.
The whole setup packs away in a study roller case (which I got used which is why it’s so beat up). Open it up and pull the control station to the top of the box, plug it in and you are off. Favorite games like Pacman, Space Invaders, 1945, Donkey Kong and many, many more. I can now waste away many hours into the wee night playing mindless video games.
Posted in Daughter Boards, DWC IP Prototyping Kits, FPGA-Based Prototyping, Getting Started, Humor, Mick's Projects | Comments Off
Posted by Michael Posner on 13th December 2014
Warning: Technical Content!
I read an online article this week which flagged an issue with FPGA-based prototyping, clock conversion. Clock conversion is one of the most important aspects to successful prototyping and this week’s blog is dedicated to sharing information enabling you to be successful. Specifically I will cover automated Gated Clock Conversion, GCC, as the user realizes the highest benefits. With automated gated clock conversion you don’t need to maintain a separate RTL code branch for prototyping, you use the golden RTL source. Clock conversion done right ensures the prototype runs at the highest performance functionally equivalent to the source. If you look at the data from the Channel Media survey that Synopsys had conducted you see that for large FPGA-based prototyping, clock conversion is a major challenge.
Hold on, I forgot to cover why clock conversion is needed for FPGA-based prototyping. It’s one of the three laws, ASIC are not the same as FPGA’s, specifically in this case FPGA’s do not have the same clock resources like ASIC’s do. ASIC designs often use clock gating to reduce dynamic power and have complex clock logic to generate numerous internal clocks. In the ASIC flow, users do Clock Tree Synthesis to balance all the clock paths between the sources and destinations and avoid clock skews between them. The problem is the number of ASIC clocks in the design typically exceed the number of global clock lines available in the FPGAs. There are a limited number of dedicated global clock lines in FPGA devices and Global clock lines cannot accommodate clock generating and gating logic. Thus GCC is needed to convert these ASIC clock structures to FPGA comparable structures. You could do this manually but that’s time consuming and error prone.
In Emulation oversampling type techniques are used to solve this problem, this is where all clocks are resolved to one synchronous clock source and all clocks are driven from derivatives of this clock. The benefit of this technique is that the conversion is fast and practically any type of clock tree structure can be handled. The main two disadvantages are #1 you tank performance as the system frequency is dictated by the slowest clock. #2 the design loses some fidelity as all clocks are synchronous to each other which may not reflect the true asynchronous clock behavior hiding issues in clock domain crossing circuits. Techniques similar to this such as the HAPS Clock Optimization in ProtoCompiler (I think I’ll blog about HAPS Clock Optimization in the future but for today I’ll focus on Gated Clock Conversion) which map clocks to HAPS hardware resources, are getting popular in FPGA-based prototyping as they can help reduce the time to first prototype enabling a prototype to be handed off to the software teams quickly. It will not have the high performance expected by the software engineers but it’s available quickly, handles almost any ASIC clock structures and this gives the prototype engineers a little breathing space to complete the high performance version.
Gated Clock Conversion, GCC, converts ASIC clock structures to FPGA friendly structures mapped to FPGA clock resources. GCC also needs to handle timing violations due to clock skew created because of clock gating logic. These violations are introduced on paths where the source and destination flops are driven by different clocks. Data from the source may reach the destination quicker/later than the clock resulting in hold/setup time violations in many paths. GCC has to ensure that there is no clock skew between two synchronous clock domains. The GCC capabilities of ProtoCompiler directly addresses both these conversion challenges in a fully automated fashion. ProtoCompiler maps to FPGA resources and moves the generated clock and gated clock logic from the clock pin of the sequential elements to the enable pins. This includes supporting implementation of these structures across block boundaries and across multiple FPGAs as part of partitioning.
Tool support of automated gated clock conversion is not a milestone it’s a journey as ASIC coding styles are continually evolving and the tools need to keep pace. ProtoCompiler has an extensive portfolio of supported structures including, but not limited to, Generated Clock, Gated Clock, Integrated Clock Gating Cells, Complex Sequential Cells, Instantiated Cells, Mixed Async Controls, Data Latches and MUX / XOR structures. With the correct clock constraints ProtoCompiler should automatically identify these gated clock structures and convert them to FPGA friendly structures. Below is an example of generated clock identification and the result of the automatic conversion.
In summary clock conversion is essential to successful prototyping. The ProtoCompiler Clock Conversion capabilities moves the generated clock and gated clock logic from the clock pin of the sequential elements to the enable pins, allowing sequential elements to be tied directly to the source clock, removing skew issues and reducing the number of clock sources in the design making it FPGA-based prototype friendly. Automated Gated Clock Conversion is just one of the many capabilities that ProtoCompiler delivers and is essential for prototypers.
Don’t forget that the FPGA-based Prototyping Methodology Manual, FPMM, has a section to help understand clock conversion and other ASIC design structure handling. Last week I had the pleasure to hang out with Rene Richter, one of the authors of the FPMM. Rene signed a book copy for me, this copy could be yours if you comment and answer the following question
How many HAPS systems has Synopsys shipped and to how many customers?
Answer the question by comment and if you get the answer right I will contact you to get your shipping addresss.
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Posted in ASIC Verification, FPGA-Based Prototyping, Man Hours Savings, Technical, Tips and Traps | 2 Comments »
Posted by Michael Posner on 14th November 2014
Recently Synopsys promoted that “Synopsys Virtual Prototyping Book Achieves Milestone of More Than 3000 Copies in Distribution to Over 1000 Companies” – http://news.synopsys.com/2014-11-05-Synopsys-Virtual-Prototyping-Book-Achieves-Milestone-of-More-Than-3000-Copies-in-Distribution-to-Over-1000-Companies Virtual Prototyping continues to gain momentum including Hybrid Prototyping, which combines Virtual Prototyping with FPGA-based prototyping. The VP book statistics prompted me to have a look at the FPGA-based Prototyping Methodology Manual, FPMM statistics.
To date there have been over 6000 FPMM downloads across 2800 different companies and over 2500 free books handed out. WOW. I expect a bit of overlap between the two but still that’s got to be over 8000 copies distributed. I’m happy that the FPMM has been able to help so many engineers around the world.
Looking at the challenges facing these prototypers, below image, you can see that conversion of ASIC to FPGA is still rated as #1.
Actually the #2 challenge, clocking issues, really falls into the this same category. As previously blogged, these challenges are not solved with just software or just hardware changes, they are solved by integration. When the software has built in understanding of the hardware and when the hardware can be customized to the needs of the SoC many of the challenges disintegrate.
A great example of the value of integration is the DesignWare IP Prototyping Kits which are part of the Synopsys IP Accelerated Initiative. DesignWare IP prototyping kits deliver a comprehensive IP subsystem which enables immediate productivity for both Hardware and Software engineers. Individually IP & FPGA-based prototyping deliver value but when combined the value is increased. It’s like the 1+1 = 3.
Talking of IP, DesignWare USB 3.1 IP is now available. http://www.synopsys.com/Company/PressRoom/Pages/usb-3-1-news-release.aspx . I have been talking about USB 3.1 for a while now and blogged about it here. You can also find a video of the DesignWare IP for USB 3.1 running on the HAPS-70 systems here https://www.youtube.com/watch?v=isQ7cvuyoTw
Do you have a topic you would like me to blog about? If so, drop me a comment and I’ll pop it in the queue.
Posted in FPGA-Based Prototyping, FPMM Methods, Getting Started, IP Validation, Technical, Tips and Traps | 1 Comment »
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