undefined | Better HN

0 pointsvrinsd4mo ago0 comments

Author: Thanks for taking the time to reply.

I read the write-up with a LOT of interest, this is really amazing work, there's not a lot of good options for auto-routing with open-source PCB tools (i.e. KiCad). I have also used the other autorouter you mentioned for "low-complexity" boards in KiCad and it helped do the job but was painful.

In my career I've also used the autorouter built into the "high-end" PCB tools and they could handle the complexity of boards you outlined WITHOUT needing a massive GPU, but they also paid people to improve this stuff over 15-to-20-years and development happened when single-core computers with limited RAM were the norm.

On the technical side, somewhat more recent FPGA 'placement' algorithms used a simulated annealing algorithm, while what you didn't isn't about placement, that approach could posisbly help with 'net cross-over reduction' type of passes, and maybe help with designs where you can do port swap / pin swap.

I'm amused you made a RISC-V array with discrete parts -- I'm sure you considered using an FPGA? Jan Gray has done > 1000+ RISC-V cores (https://fpga.org/grvi-phalanx/) in "older" Xilinx FPGAs.

If you're trying to emulate Thinking Machines / CM-x or anything else, frankly I think a "mondo" FPGA is still the way to go.

Job-wise: A suggestion might be to reach out to the guys at AllSpice ( allspice.io ) who make revision control software for Altium and possibly KiCad. The work you did to enable IPC, etc seems like exactly the type of skillset these guys might need (contractor, maybe full-time?) to interoperate with KiCad.

If I see anything that might be up your alley I'd also reach out. I'm not in a position to hire anyone and while "some companies" may not be impressed by what you did, the right organization WOULD be.

I share your sentiment that the likes of "modern" companies like Apple, MSFT, etc the hiring process is really taylored to "I want a guy who can do X" and rarely "I want a guy who's shown he can learn Y and Z so he can certainly do X".

0 comments

wanderingjew4mo ago

> On the technical side, somewhat more recent FPGA 'placement' algorithms used a simulated annealing algorithm, while what you didn't isn't about placement, that approach could posisbly help with 'net cross-over reduction' type of passes, and maybe help with designs where you can do port swap / pin swap.

Yeah, that was the first step in creating the netlist for the backplane. Simulated annealing on the 8196 nets. TO BE FAIR, this would be a lot easier to route if I didn't explicitly want each of the 16 cards to be identical, but I think that's the most cost-effective way to do it.

As far as an FPGA.... I don't know if I see the point. The nodes in the original CM-1 were basically _only_ ALUs. Very little processing power. The CM-5 was a little better, but this entire thing is batshit crazy. I might as well go for four thousand individually programmable cores. Like, what even is a MISD computer? I have no idea, so lets build one. See what it can actually do.

vrinsdOP4mo ago

If you're open to technical feedback your last comment, I've worked on these kinds of systems, have architected and built things even far "weirder" and these products have shipped and out in the real world, in silicon, in FPGAs and things between.

The reason an FPGA is a more suitable platform is you can translate "physical effort of making PCBs" into "creating a design in an infinitely re-programmable platform" and change your design as needed to your hearts content.

In fact, the original design of RISC-V included a bus called 'TileLink' to enable 'Many core' arrays of RISC-V processors.

Translation: You can pare-down open-source RISC-V cores and use TileLink and emulate CM or build something more complex as you see fit since that was built into the original open-source RISC-V specs.

FPGAs are their own joy and pain for sure and it's not as "cool" to re-program a blackbox on a PCB as it might be to make your own thing, so all depends on your goals.

actionfromafar4mo ago

I dunno. Each of these physical processors have 8 kilobytes SRAM and 62 kilobytes of some kind of flash or something. Multiply by 4096, wouldn't that be one hell of an FPGA?

1 more reply

j / k navigate · click thread line to collapse