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

[Joshua Boyd]

On 8/23/21 3:18 AM, Romain Dolbeau wrote:
> Le lun. 23 aoC;t 2021 C  00:39, Richard <ejb at trick-1.net> a C)crit :
>> If you are thinking of making a small run available at some point I for one
> would be very interested.
>
> Thanks for the vote of confidence :-) but I'm not sure the numbers add up...
>
> The off-the-shelf FPGA board itself will already set you back >150b,
> (incl. VAT, excl. shipping) from the company in Germany - if you pick
> the smallest FPGA (which I did, and it's probably enough).
>
> And then the custom carrier gets expensive for very small numbers;
> last time I got 5 PCBs with only 2 populated and it was about 300b,. A
> 10+ full run could probably bring the price down to 100b,/piece (maybe
> even a bit less), but that's still an expensive proposition at around
> 250b, for the 'finished' product - assuming there would be a market for
> at least 10! And with no support for SunOS 4 or Solaris 2.x/7/8 at
> all, only NetBSD...
>
> Also it is too tall to fit in the SBus specifications (those 2.54mm
> headers are tall, and I added a radiator on the FPGA just in case), so
> you need to put it in a bottom slot of a 10/20 (haven't tried it in
> anything but a couple of 20s yet so no idea about other SPARCstations)
> and it will block the top one - and might cause airflow issue (it's
> not that hot by itself, though).
>
> I might do another set of PCBs with proper USB support and more
> interrupt lines connected, but I won't know if all that will work
> until I've tested them - so it doesn't make sense to do a bunch of
> them beforehands (I'm no PCB expert, hence the lack of high-speed
> stuff like HDMI :-( ).

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.