20 Nov
2006
20 Nov
'06
10:09 p.m.
Brad Parker wrote:
"Chuck Guzis" wrote:
> Not vintage, but closely related.
>
> Rather than write some emulation software, I'd like to see if I can
> implement some simpler CPU designs in FPGA.
>
> I see various development kits out there with various capabilities
> (I/O memory, displays, etc.).
>
> Is there any particular kit that stands heads and shoulders above the
> others? Is there a preference between Xilinx and Altera?
I, too, really like
the boards from digilent (http://www.digilentinc.com/).
They have a number of different styles from low end CPLDs to very high end
FPGAs (only Xilinx, though). I've used both their older Pegasus (Spartan2)
and the newer Spartan3 boards.
Xilinx supplies the free webpack synthesis tools (http://www.xilinx.com)
of course.
For simulation I also recommend gpl-cver
(http://www.pragmatic-c.com/gpl-cver)
for verilog under cygwin (http://www.cygwin.com) on WinXP. For viewing
waveforms
I use dinotrace (http://www.veripool.com/dinotrace/).
Using all these pieces I was able to implement a PDP-8e (no EAE, at
least yet)
that passes all the basic CPU diagnostics. Cast in hardware on the digilent
Pegasus it occupies about 13% of an XC2S200-6, and runs at 15ns per
clock tick
(4 ticks per cycle), which is about 20X faster than a real PDP-8m
(1200ns/60ns).
The base CPU is about 500 lines of verilog.
Don