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Re: First new vax in ...30 years? :-)

  This is TANTALIZING!!!  Amazing work Ragge.  I might be interested in
doing a system-level design around this!


On 7/3/21 6:14 AM, Anders Magnusson wrote:
> some time ago I ended up in an architectural discussion (risc vs cisc
> etc...) and started to think about vax.
> Even though the vax is considered the "ultimate cisc" I wondered if its
> cleanliness and nice instruction set still could be implemented
> efficient enough.
> Well, the only way to know would be to try to implement it :-)  I had an
> 15-year-old demo board with a small low-end FPGA (Xilinx XC3S400), so I
> just had to learn Verilog and try to implement something.  And it just
> passed EVKAA.EXE:
>>FR00000000 200
> EVKAA V10.4 Hardcore Instruction Test
> Hit any key to continue
> EVKAA   V10.4 pass # 1(X) done!
> EVKAA   V10.4 pass # 19(X) done!
> EVKAA   V10.4 pass # 32(X) done!
> EVKAA   V10.4 pass # 4B(X) done!
> EVKAA   V10.4 pass # 64(X) done!
> EVKAA   V10.4 pass # 7D(X) done!
> EVKAA   V10.4 pass # 96(X) done!
> EVKAA   V10.4 pass # AF(X) done!
> EVKAA   V10.4 pass # C8(X) done!
> EVKAA   V10.4 pass # E1(X) done!^C
> Input breakpoint: 000000001
> (the microcode console works like the Nova4 microcode console - simpler
> to implement than the VAX style...)
> It runs at 50MHz, but could easily be increased to about 80, just to
> program DCM.
> Photo of the "vax": https://www.ludd.ltu.se/~ragge/pics/IMG_0837.jpg
> I had to get a new FPGA board, since I started to get bit errors on the
> old one, so I bought a chinese board with essentially the same FPGA
> (XC3S500E):
> I have implemented all addressing modes, the interrupt hierarchy,
> timers, and 151 instructions.
> No memory management yet though, but that should be quite straight-forward.
> Currently it uses about 70% of available FPGA resources, which is around
> 6000 LUTs (which is quite inefficient implemented, since I have learned
> how to do verilog programming while writing the code...)
> I'll follow up this mail with two more, one about the implementation and
> one about how to go forward with the vax architecture :-)
> -- R

Dave McGuire, AK4HZ
New Kensington, PA

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