5 ms·

"Wow?" This is actually disappointingly low raw TFLOPS performance. Intel's Knights Ferry GPGPU ASIC is not yet available, but already outperformed by 2-year-o

by mrb 15y ago

"Wow?" This is actually disappointingly low raw TFLOPS performance. Intel's Knights Ferry GPGPU ASIC is not yet available, but already outperformed by 2-year-old chips from AMD and Nvidia who have both been selling GPU ASICs breaking the 1 TFLOPS barrier (single precision) for over two years now. The AMD Radeon HD 5870 and HD 6970 both reach 2.7 TFLOPS, and AMD makes a dual-ASIC PCIe card HD 6990 reaching 5.1 TFLOPS. Nvidia's mid-level GTX 275 (1.01 TFLOPS) was released in April 2009. In fact, Knights Ferry evolved from the Larrabee GPU project, which disappointed Intel so much in terms of performance that they decided to forgo the GPU market (as it was clearly not going to be competitive), and to remain focused only on the GPGPU market by evolving Knights Ferry from Larrabee. The one strong advantage of Knights Ferry is not performance, but x86 compatibility, as it would theoretically make it easy to port programs to. Although one would still have to rewrite the app to use the LRBni instruction set (512-bit regs) to fully exploit the computing performance... or else one would be limited to a quarter of its potential with SSE (128-bit regs.) Another relative advantage of Knights Ferry is that each of the 50+ cores will probably be able to execute 50 unique instructions every clock cycle, making it very flexible. (Compared to, say, the HD 6970 which has 384 "cores" or VLIW units only able to execute 24 unique instructions: the ASIC is organized in 24 SIMD engines of 16 VLIW units each, the 16 VLIW units in each SIMD engine execute the same instruction in 16 different thread contexts, for a total of 384 threads.) Edit: my bad, it looks like Intel claims 1 TFLOPS in double precision, which would put it up to the level of upcoming AMD chips (HD 7970 rumored to provide 4.1 SP TFLOPS or 1.0 DP TFLOPS in early 2012.)

stuntprogrammer 15y ago
A few problems in your comment: 1) The article text is wrong (and doesn't match the pics of the slides). The chip demonstrated today is Knights Corner which is a new part, not the older Knights Ferry SDV. 2) When counting flops we need to distinguish between single precision flops and double precision flops. You're comparison isn't valid -- Knights Corner was shown sustaining over 1TF on a double precision code. Nvidia's most recent flagship GPU has a theoretical peak of 515GF/s but sustains less than 225GF/s on the same DGEMM operation. Knights Corner is sustaining 4-5x that, and this implies that it's theoretical peak is higher again. AMD's GPUs also cannot touch this with a single chip. Their dual chip 6990 has what looks like the same theoretical peak but far lower practical performance due to being more of a graphics part than a compute part (e.g. look at the cache structures). You are correct that these are real cores, each with a wide vector unit. If we wanted the equivalent of GPU "cores" we should multiply out by the vector width per core.
- Retric 15y ago
  This Intel chip has a theoretical max performance of 1TF/s actual benchmarks are clearly going to be lower than that. The only thing slightly interesting about this is x86 but considering the large vector unit and anemic cache your not going to be able to port high performance code to this without massive changes anyway. And while comparing new chips vs existing chips is always a tradeoff, looking at the Radeon HD 6970 released in Dec 15, 2010 which had 2.7 TFLOPs Single Precision and 683 GFLOPs Double Precision this is a relatively minor jump in single chip double precision performance and unless there releasing it next week it would probably still be far slower than it's competitors. That's also raw performance, considering this is a brand new architecture it's likely to have some significant bottlenecks limiting it's performance for the next 2-3 product cycles. PS: Considering so few details where provided it's hard to look at this as anything but Intel saying "Please don't port your code we will have competitive x86 chips out at some point in time."
  - stuntprogrammer 15y ago
    It's doing 1TF sustained and no one ever sustains 100% of their theoretical peak, so we know the peak is higher than 1TF. Consider also the sandbagging of number of cores as "50+". How big is the "+"? In reality the design will have a larger number that is then binned by yield and so forth to give a range of SKUs, as usual. Next, you're comparing a sustained number on DGEMM with theoretical peaks on other machines. Nvidia sustains <225GF on DGEMM with Fermi so this is 4-5x. Last I looked, AMD were sustaining ~500GF with Cayman, so this is 2x, and a much easier machine to sustain perf on for other codes compared to Cayman. If you consider a potentially sandbagged 2x sustained perf to be "relatively minor" then so be it. There are few public details provided but many of us have been programming with the Knights Ferry SDV kit in preparation for this part. So we have experience with the tools, with the use of lots of similar cache coherent x86 cores, etc. I can tell you this -- it's much easier to work with this than GPUs, and I've written a ton of code on all kinds of whacky machines, production compute code on GPUs included.
    - sausagefeet 15y ago
      Where can I learn more about how all this hardware works?
anigbrowl 15y ago
I guess this is partly about stealing AMD's thunder following their recent release of the 16-core bulldozer chips. Not that the technologies directly compare, but most non-geeks are just going to see 50 cores >> 16 and buy Intel again next time.
- Klinky 15y ago
  Intel MIC is competing with GPUs not CPUs.
  - anigbrowl 15y ago
    I feel you should reread the second sentence of my comment above.
    - Klinky 15y ago
      Non-geeks will not care because it will not be marketed to them or available for them to purchase. This is a High Performance Computing product going against AMD's Firestream or nVidia's Tesla. These are high dollar products for niche tasks that non-geeks won't be doing. Non-geeks will be listening to what the salesman tells them is good, not referencing some blurb their geek friend told them about a 50-core Intel product. This product is the successor to Knights Ferry which was a 32-core part released way-way-way before Bulldozer.
rbanffy 15y ago
> Although one would still have to rewrite the app to use the LRBni instruction set (512-bit regs) to fully exploit the computing performance... http://drdobbs.com/architecture-and-design/216402188 http://drdobbs.com/architecture-and-design/216402188 ("A First Look at the Larrabee New Instructions")

by mrb 15y ago

stuntprogrammer 15y ago

A few problems in your comment: 1) The article text is wrong (and doesn't match the pics of the slides). The chip demonstrated today is Knights Corner which is a new part, not the older Knights Ferry SDV. 2) When counting flops we need to distinguish between single precision flops and double precision flops. You're comparison isn't valid -- Knights Corner was shown sustaining over 1TF on a double precision code. Nvidia's most recent flagship GPU has a theoretical peak of 515GF/s but sustains less than 225GF/s on the same DGEMM operation. Knights Corner is sustaining 4-5x that, and this implies that it's theoretical peak is higher again. AMD's GPUs also cannot touch this with a single chip. Their dual chip 6990 has what looks like the same theoretical peak but far lower practical performance due to being more of a graphics part than a compute part (e.g. look at the cache structures). You are correct that these are real cores, each with a wide vector unit. If we wanted the equivalent of GPU "cores" we should multiply out by the vector width per core.

Retric 15y ago
This Intel chip has a theoretical max performance of 1TF/s actual benchmarks are clearly going to be lower than that. The only thing slightly interesting about this is x86 but considering the large vector unit and anemic cache your not going to be able to port high performance code to this without massive changes anyway. And while comparing new chips vs existing chips is always a tradeoff, looking at the Radeon HD 6970 released in Dec 15, 2010 which had 2.7 TFLOPs Single Precision and 683 GFLOPs Double Precision this is a relatively minor jump in single chip double precision performance and unless there releasing it next week it would probably still be far slower than it's competitors. That's also raw performance, considering this is a brand new architecture it's likely to have some significant bottlenecks limiting it's performance for the next 2-3 product cycles. PS: Considering so few details where provided it's hard to look at this as anything but Intel saying "Please don't port your code we will have competitive x86 chips out at some point in time."
- stuntprogrammer 15y ago
  It's doing 1TF sustained and no one ever sustains 100% of their theoretical peak, so we know the peak is higher than 1TF. Consider also the sandbagging of number of cores as "50+". How big is the "+"? In reality the design will have a larger number that is then binned by yield and so forth to give a range of SKUs, as usual. Next, you're comparing a sustained number on DGEMM with theoretical peaks on other machines. Nvidia sustains <225GF on DGEMM with Fermi so this is 4-5x. Last I looked, AMD were sustaining ~500GF with Cayman, so this is 2x, and a much easier machine to sustain perf on for other codes compared to Cayman. If you consider a potentially sandbagged 2x sustained perf to be "relatively minor" then so be it. There are few public details provided but many of us have been programming with the Knights Ferry SDV kit in preparation for this part. So we have experience with the tools, with the use of lots of similar cache coherent x86 cores, etc. I can tell you this -- it's much easier to work with this than GPUs, and I've written a ton of code on all kinds of whacky machines, production compute code on GPUs included.
  - sausagefeet 15y ago
    Where can I learn more about how all this hardware works?

anigbrowl 15y ago

I guess this is partly about stealing AMD's thunder following their recent release of the 16-core bulldozer chips. Not that the technologies directly compare, but most non-geeks are just going to see 50 cores >> 16 and buy Intel again next time.

Klinky 15y ago
Intel MIC is competing with GPUs not CPUs.
- anigbrowl 15y ago
  I feel you should reread the second sentence of my comment above.
  - Klinky 15y ago
    Non-geeks will not care because it will not be marketed to them or available for them to purchase. This is a High Performance Computing product going against AMD's Firestream or nVidia's Tesla. These are high dollar products for niche tasks that non-geeks won't be doing. Non-geeks will be listening to what the salesman tells them is good, not referencing some blurb their geek friend told them about a 50-core Intel product. This product is the successor to Knights Ferry which was a 32-core part released way-way-way before Bulldozer.

rbanffy 15y ago

> Although one would still have to rewrite the app to use the LRBni instruction set (512-bit regs) to fully exploit the computing performance... http://drdobbs.com/architecture-and-design/216402188 http://drdobbs.com/architecture-and-design/216402188 ("A First Look at the Larrabee New Instructions")