[rescue] SBusFPGA update: USB Host, 256 MiB DDR3 RAM disk, ... (Was: Re: A SBus card for SPARCstation designed in 2020...)

[Romain Dolbeau]

Le lun. 23 aoC;t 2021 C  22:32, Joshua Boyd <jdboyd at jdboyd.net> a C)crit :
> I wonder how reasonable it would be with nmigen to support multiple
> FPGAs. This normally seems to be unpleasant for people writing Verilog
> or VHDL directly.

I'm not sure the single-design, multi-FPGA market is that big - and
probably doesn't justify the effort for something like (n)Migen...

The SBusFPGA fits comfortably in a 35k cells Artix-7
Litex can do a Quad-core RV32GCBK + peripherals with room to spare in
a 100k cells Artix-7.
Virtex Ultrascale+ and other high-end FPGAs can have millions of cells
and can fit fairly complete RV64GCV SoCs.

By the time a single design needs to scale over multiple FPGAs, you're
probably in the 'validating a production SoC' kind of job, or
something on a similar scale of effort. And the hardware needed is
probably hideously expensive to come by (a VCU128 board with a single,
middle-of-the-range Virtex Ultrascale+ FPGA is already $9k...).

Cordially,

--
Romain Dolbeau