[Libre-soc-dev] ls180 update

Jean-Philippe Turcotte jp2k5 at hotmail.com
Mon Apr 19 00:53:15 BST 2021

> yes - the specs for the first phase (yosys turns HDL into gate-level
> BLIF, coriolis2 turns that back into VHDL, yosys turns that into
> Verilog, verilator compiles that to c++) [...]

First of all, thank you for your detailed answer. I know you are quite busy right now.

It is not clear on the HDL workflow page, but to get up and running I would need to run the dev-env-setup script, and then install yosys and coriolis2, correct? Can I use Debian 10 for this?

> [...] would be that each machine
> would require at least 128 GB of RAM, and to complete in a reasonable
> time-frame at least 100 machines would be required.
> for the second phase (coriolis2 completes place-and-route, coriolis2
> extracts P&R as VHDL, yosys turns that into Verilog, verilog compiles
> that to c++) would require machines with 5x those resources and
> require 10x those numbers of machines.
> that's 1,000 machines, with 512 GB of RAM in each machine (1 TB of RAM
> may be needed).

Okay, here is my idea:

First, I need to start with a smaller example to reduce the compilation time, and check that the method works. I can use a high-memory cloud VM (I do not know what is available to trial users, but 512 GB seems easily accessible, potentially up to 5 TB) to generate the C++.

Second, it seems I could use gg (https://github.com/stanfordsnr/gg) to compile the C++ on tens of thousands of transient VMs to get the executable in a human timeframe.

Third, I suppose we can somehow test that the simulation produces accurate results.

Fourth, if everything works, and we can estimate with confidence that it will not cost into the thousands, I can go for the full core.

Cloud providers offer credits (mostly around US$300) to try out their infrastructure, so with good planning we might get it done for free.

> paradoxically, there are reports online that if threading is used
> verilog simulations can go slower.

I would definitely benchmark this with the smaller example before going any further.

> i will ask NLnet if they have anything.
> l.

That would be great!

By the way, sorry for the weird list reply. I was in digest mode, so I did not have an email to which I could reply.


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