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I've looked into FPGAs that are connected to PCIe and provide high throughput to the host, but it seems these are always in the thousands of dollars. What's pr
by incrudible 6y ago
I've looked into FPGAs that are connected to PCIe and provide high throughput to the host, but it seems these are always in the thousands of dollars.
What's preventing the FPGA AIB from becoming a commodity like a GPU? Is it just economics of scale, or are these things fundamentally more expensive?
- structural 6y agoIt's somewhat economics of scale, but also that small/cheap FPGAs are sized rather closer to what you'd expect in a microcontroller (and that is quite sufficient for many designs). Supporting PCIe and other high-speed interfaces (10Gb ethernet and beyond, etc) requires physical transceivers which look a whole lot more like "wireless communications over a PCB trace" and less like the traditional "drive a digital signal over a GPIO pin". These interfaces also typically drive requirements for data buffering as well as higher clock rates: all of these things increase size and cost. That said, you can get basic chips that will do this for much less than "thousands of dollars" - Xilinx's Artix line is optimized for low cost + relatively high numbers of transceivers compared to the number of logic cells. You'd probably be interested in a development board something like the PicoEVB, which is in the USD $200 range and provides a M.2 form factor / PCIe interface to a FPGA. The actual FPGA itself to do this can be had for less than this... but the cost of the PCB, connectors, adding DDR memory, etc., etc., do start to add up.
- mng2 6y agoThe most reasonable board for hobby PCIe (< $100) right now is probably the SQRL Acorn, it was designed for mining but it turned out to be pretty useless for that purpose. There are cheaper FPGAs with PCIe support coming onto the market, but they tend to be low on fabric since they are designed for low end applications (Lattice Crosslink NX). I think there are a few fundamental problems with FPGA compute offload. First is that, as niche products, FPGAs are always a node or two behind the leading edge, so their logic gates run slower than CPUs and GPUs; even their "hard" compute blocks are not as fast. Second, the fundamental nature of FPGAs as a "sea of logic" mean that routing delays reduce your max frequency, or make pipelining necessary thereby incurring latency. Third is memory; historically, FPGAs have not supported high-bandwidth GDDRx, and if you're crunching on something you generally want bandwidth. The latest high-end FPGAs do have HBM but they are quite expensive. So why would anyone want something that's slower and more expensive? Well, you have to be doing something special, like a lot of custom parallel processing pipelines, or with hard realtime requirements. Basically, a niche, and that doesn't lend itself to economies of scale.
- homarp 6y agoSQRL Acorn are 'second-hand' eBay only To get started once you get one, it's supported by https://github.com/litex-hub/litex-boards https://github.com/litex-hub/litex-boards https://www.element14.com/community/community/project14/hardwarehacking/blog/2020/07/13/sqrl-oak-dev-board-finishing-up https://www.element14.com/community/community/project14/hard... links to more or less everything you need to know.
- homarp 6y agoand also https://github.com/enjoy-digital/litex/wiki/Use-LiteX-on-the-Acorn-CLE-215 https://github.com/enjoy-digital/litex/wiki/Use-LiteX-on-the...
- the_only_law 6y agoI know hardly anything about actually using FPGA’s (though learning would probably make my life easier), but when I was doing research a while back I found some Lattice ones which were ~$200. No idea if they are capable of what you’d want to do.
- mciancia 6y agoThere are some chinese FPGA card that you might find interesting: https://pl.aliexpress.com/item/1005001275162791.html https://pl.aliexpress.com/item/1005001275162791.html
- mastax 6y agoThat chip is $967 on Digikey, yet that entire dev kit is $259. It's annoying that the only way to get reasonably priced FPGAs is to launder them through China.
- RantyDave 6y agoThe problem is floating point math. Mostly we want GPU's (and TPU's) to crunch floating point match really quickly. However, FP units are complicated things and take a disproportionate amount of FPGA fabric. Add to this the lower clock speed and suddenly GPU's start to look really cheap.
- egsmi 6y agoSome FPGAs are commodities. Here’s one with a PCB for $13. Can be used with an open tool chain too. I could probably find an even cheaper one if I looked harder. https://store.tinyfpga.com/products/tinyfpga-a1 https://store.tinyfpga.com/products/tinyfpga-a1 Just like with GPUs, FPGAs with bigger die areas cost more. The biggest ones are expensive, just like with GPUs.
- ajfjrbfbf 6y agoAll TinyFPGAs are sold out for now :(
- egsmi 6y agoInteresting. The AX is out but the AX1 ($15) is in stock. https://www.crowdsupply.com/tinyfpga/tinyfpga-ax-bx https://www.crowdsupply.com/tinyfpga/tinyfpga-ax-bx I suppose the price is a bit misleading because the AX also requires the $12 programmer so with shipping+tax to CA it's closer to $30 total out of pocket. Personally I use the BX because having the flash, and a bit more logic, is convenient.
- snvzz 6y agoThe AX is not iCE40, thus no icestorm support, and it is tiny. Few designs can fit in there. Do look for iCESugar on aliexpress instead.