Why Use an FPGA Instead of a CPU or GPU? • Hacker News Board

Re: Why Use an FPGA Instead of a CPU or GPU?

#11

Post by opencl » Tue, Aug 14, 2018, 2:25 PM UTC

rini17 wrote: post #3

Is there high performance FPGA that does not depend on proprietary bloated windows-only toolchain?

Every FPGA I have used has offered their proprietary bloated incredibly expensive toolchain on Linux.

There's icestorm but the supported hardware is not exactly high performance, IIRC the biggest chips supported have around 8K LUTs.

Re: Why Use an FPGA Instead of a CPU or GPU?

#12

Post by jeffreyrogers » Tue, Aug 14, 2018, 2:30 PM UTC

radarsat1 wrote: post #4

rini17 wrote: post #3

Is there high performance FPGA that does not depend on proprietary bloated windows-only toolchain?

Proprietary and bloated yes, but I believe both Xilinx and Altera both have software available for Linux, or am I wrong? At least I used Altera's suite on Linux once for a pilot project.

I have used Xilinx's toolchain on Linux, though it was hard to get working. This was a few years ago.

Re: Why Use an FPGA Instead of a CPU or GPU?

#13

Post by monocasa » Tue, Aug 14, 2018, 2:34 PM UTC

antoineMoPa wrote: post #5

"Intel does offer an emulator, so testing for correctness does not require this long step, but determining and optimizing performance does require these overnight compile phases." After some experience with FPGAs, the emulation step is not enough to test for correctness. Most of the problems happen while synchronizing signals with inputs/outputs and with other weird timing problems, glitches and unintuitive behavior…

I wouldn't think the normal standard issues with glitches and synchronizing signals would happen with OpenCL. The synthesizer should have enough information to handle all of that and spit out max timing on the other side.

Re: Why Use an FPGA Instead of a CPU or GPU?

#14

Post by rwmj » Tue, Aug 14, 2018, 2:36 PM UTC

I'm surprised he doesn't talk much about direct cost (rather than engineering cost). A decent FPGA developer kit will cost several thousands of US$, more expensive even than high end GPUs.

Re: Why Use an FPGA Instead of a CPU or GPU?

#15

Post by jaxtellerSoA » Tue, Aug 14, 2018, 2:39 PM UTC

Aren't FPGA's used mostly to test/design a circuit that you would then go on to actually fabricate/build? I could be wrong but I thought FPGA's were stateless (meaning if they powered off/reboot you loose everything and have to set it up from scratch again).

Re: Why Use an FPGA Instead of a CPU or GPU?

#16

Post by rwmj » Tue, Aug 14, 2018, 2:39 PM UTC

rini17 wrote: post #3

Is there high performance FPGA that does not depend on proprietary bloated windows-only toolchain?

Supposedly some of the Xilinx 7 series FPGAs have been reverse engineered so there is a possibility of supporting them in Yosys (which is reasonable free toolchain). I've not been able to get much information about this, but you can check on the website: http://www.clifford.at/yosys/

Re: Why Use an FPGA Instead of a CPU or GPU?

#17

Post by amelius » Tue, Aug 14, 2018, 2:43 PM UTC

One reason could be to meet real-time constraints or to get predictable timing. This is becoming more and more difficult to do with modern CPUs for all sorts of reasons.

Re: Why Use an FPGA Instead of a CPU or GPU?

#18

Post by zwieback » Tue, Aug 14, 2018, 2:45 PM UTC

jaxtellerSoA wrote: post #15

Aren't FPGA's used mostly to test/design a circuit that you would then go on to actually fabricate/build? I could be wrong but I thought FPGA's were stateless (meaning if they powered off/reboot you loose everything and have to set it up from scratch again).

Yes and yes but new uses are emerging, it's like 3D printing: there's a crossover where the extra cost you pay for flexibility becomes too much to compete with hard wired logic despite the high initial cost.

Re: Why Use an FPGA Instead of a CPU or GPU?

#19

Post by stumpylog » Tue, Aug 14, 2018, 2:45 PM UTC

jaxtellerSoA wrote: post #15

Aren't FPGA's used mostly to test/design a circuit that you would then go on to actually fabricate/build? I could be wrong but I thought FPGA's were stateless (meaning if they powered off/reboot you loose everything and have to set it up from scratch again).

No, they retain state. We used an Altera DE1 in school and it retained our burnt in program until erased or reprogrammed

Re: Why Use an FPGA Instead of a CPU or GPU?

#20

Post by delroth » Tue, Aug 14, 2018, 2:45 PM UTC

jaxtellerSoA wrote: post #15

Aren't FPGA's used mostly to test/design a circuit that you would then go on to actually fabricate/build? I could be wrong but I thought FPGA's were stateless (meaning if they powered off/reboot you loose everything and have to set it up from scratch again).

Many FPGAs can load their bitstream from Flash.