FPGA VAX update

[Ken Seefried]

From: Johnny Billquist <bqt at Update.UU.SE>
> I think I have the documentation for the microcode for 
> the different engines, and I also have the binary microcode 
> files... 

Do you have the microcode files for the 11/730?  

The Am2901 VHDL (and other formats) is freely availible and well understood and fits several to an FPGA (even small ones covered by free tools).  The rest of the logic on an 11/730 CPU isn't that terrible complicated.  Given access to the microcode, I'd imagine it would be a reasonable project to whip up an ersatz 11/730, validate that it works correctly, then proceed to optimize and otherwise improve the design (add in pipelining, test, add in FPU, test, add in cache, test, migrate to faster FPGA family, test).  Iterative, rather than shooting the moon first run.  

You could even short-cut some of the FPGA work.  I don't recall what the microsequencer looks like on the 11/730, but if it's the usual Am29{09,10,11}, there is at least one shop that still (as of at least last year) makes an 8 x Am2901 + sequencer single chip ASIC that runs at something like 20MHz.  Or you can find NOS for the IDT 49c402 that is 4 x Am2901s.

This way of thinking won't result in the fastest VAX possible, but I venture it has a better chance of resulting in an actual working VAX.

> Anyone want to take a crack at this? :-)

Not me...:-)

Ken