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

[Toby Thain]

On 2021-08-24 6:19 a.m., Romain Dolbeau wrote:
> 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...
> 

I think the phrase "multiple FPGAs" probably meant portability to
multiple vendors, not "more than one". Hence the reference to nmigen.

> 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
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