FPGA VAX update

[Johnny Billquist]

On Tue, 25 Oct 2005, Ken Seefried <ken at seefried.com> wrote:

> 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?

Might still have the TU58 tapes around, yes. No TU58 drive to read them,
though.

> 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.

Maybe. I think that there is probably a lot more logic outside the 2901
than inside... We're still talking several boards of logic here... I doubt
all of that is microcode memory, 2901s and 74xx series stuff. :-)

> 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.

It might be a possiblity. Not that I'll do it. But if someone really
wanted this to happen, it's one possibility. Might be easier to talk with
someone who still have an 11/730 running, to read his tapes though.

> > Anyone want to take a crack at this? :-)
>
> Not me...:-)

:-)

	Johnny

Johnny Billquist                  || "I'm on a bus
                                  ||  on a psychedelic trip
email: bqt at update.uu.se           ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol