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> At all computer sizes, a GPU probably will have more multiply circuits than an equivalent cost FPGA Very likely yes, but FPGAs often have hundreds to thousan

• pkaye 3y ago
  How much would that FPGA cost?
• UncleOxidant 3y ago
  The FPGAs with enough multipliers to be competitive against an actual GPU are going to be quite a bit more expensive than a GPU aren't they?
• mathisfun123 3y ago
  I wish people would stop quoting marketing material as some kind representation of what they know. You're giving completely the wrong impression about dsp slices - it is absolutely not 1 dsp slice per FP operator at any precision that you would want to do floating point arithmetic. It's definitely at least 2 plus a whole bunch of LUTs (~500) for FP16 with 4 stages or something like that. And if you want faster (fewer stages) then you need more slices. On alveo u280, which is an ultrascale part, I have never been able to effectively utilize more than ~4000 dsp slices (out of 9024) for 5,4 mults and that cost basically 99% of clbs in SLR1 and SLR2. And even then, disconnected FPUs are completely meaningless without a datapath implementing eg matmul and boy oh boy do you have no clue what you're in for there. Takeaway: it's pointless to compare raw specsheet numbers when everything comes down to datapath.
  • gsmecher 3y ago
    > everything comes down to datapath. Ain't that the truth. However: Xilinx's DSP58 blocks (Versal devices), and older Intel DSPs, do integrate floating point into the DSP tiles - which does narrow the gap between the datasheet's DSP count and the number of floating-point operations achievable per clock.
    • mathisfun123 3y ago
      > Xilinx's DSP58 blocks (Versal devices) this is correct (i am currently working on designs that target these parts) but those things are more expensive than comparably sized/equipped nvidia gpus so (in the context of this discussion) it's moot.
      • rzzzt 3y ago
        Ballas mentions in a neighboring reply that the eGPU from the paper is using an Agilex 7: https://ark.intel.com/content/www/us/en/ark/products/217645/intel-agilex-7-fpga-fseries-014-r24b.html https://ark.intel.com/content/www/us/en/ark/products/217645/...
        • mathisfun123 3y ago
          Yes but as you can see by reading, this comment chain starts with someone linking to a xilinx product
  • Ballas 3y ago
    The Intel Agilex (that was used in this paper) DSP blocks natively support single and half precision floating point.
• dragontamer 3y ago
  And my 6-year-old Consumer GPU (Vega64) has 4096 32-bit multipliers at 1500 MHz clock. (And I bought it a year or two late, so it was only $400). With 8GB HBM2 RAM at 512GBps (yes, Gigabytes per second) throughput. You absolutely are not getting anything close to a consumer GPU in terms of performance or cost on any other platform. --------- FPGAs advantage is that systolic array arrangement. I'm pretty sure GPUs will win in a "hardware multiplier" war, but it might be harder to get all the data into a typical GPU There's a fair number of programs that will never utilize a GPU with any level of efficiency. That's where FPGAs come in, utilization will be better because of LUTs and Routers and all that magic. But if people are looking for a TFLOP fight with raw numbers of multipliers? My bet is on the GPU and SIMD-processing in general. Those architectures are just crazy. -------------- BTW: That top end DSP slice is documented here: https://docs.xilinx.com/v/u/en-US/ug579-ultrascale-dsp https://docs.xilinx.com/v/u/en-US/ug579-ultrascale-dsp That's a 27-bit x 18-bit multiplier per dsp. In contrast, a 32-bit floating point operation is 24-bit x 24-bit multiplier plus a bit of extra stuff for the exponent bits. I'm pretty sure that the 4096-shader Vega64 actually had 32-bit multipliers but I'm not 100% sure on that. But the float 24-bit x 24-bit multiplier would need more than one dsp to replicate, maybe two of them. AMD's newest consumer 7900 xt GPUs are 6144-shader... but those shaders can execute _TWO_ multiplies per clock tick for a total of 12288 hardware multipliers operating at 2500 MHz clock.