[HECnet] PDP-11/70 on FPGA

[Johnny Billquist]

Paul Koning wrote:
On Aug 9, 2010, at 10:05 PM, Johnny Billquist wrote:
Brian Hechinger wrote:
If so I'm SOOOO buying a bunch of FPGAs to run that on. :-D
Yes, it should run most software just fine.
I have just a few gripes with this implementation. If they matter to you
or not is for you to decide:

1) No FPP. I think this is important, others might disagree.
2) Small disks. Only RK05 for now, and no plans for MSCP at all. While
future massbus is cool, by todays standards, fixed size, rather small
disks, are not that useful.
Non-MSCP disks can be done in logic; MSCP has always been implemented as firmware running on the storage controller.   Presumably you'd want to do likewise here.   That's certainly possible, with the help of an embedded processor inside the FPGA.   Then you'd have to implement the MSCP firmware, which is a fair chunk of code.   (I don't suppose anyone has the UDA50 firmware available?   Then all you'd need is an FPGA model of the hardware, which would be easy by comparison.)

I think you'll go with something akin with firmware for whatever storage you choose, since it will not map easily with any backend you choose anyway.
That said, MSCP is still more complex than anything else, I agree. But it's also more useful.

Doing the whole UDA50 hardware in an FPGA would not be useful, since then you'd have something that would talk SDI. You'll not find anything today that talks SDI.

More meaningful in that case to do the CDU720, which uses SCSI as the backend. But I still think just implementing the basic needed for MSCP straight away is easier. We have enough of MSCP already figured out, and implemented for this to not be that hard today. The sources for simh is around, which implements enough of MSCP needed. Use that as the base.
And then map it to whatever backend you want to use.

3) Backend very dependant on some host machine with OS. I guess it helps
to make it doable faster, but for me, the really nice thing would be
something like USB interface to mass storage, which looks like MSCP from
the PDP-11 side. That would be *really* cool.
By far the easiest storage interface is IDE (ATA); is that still around?   Well, it is, in CompactFlash cards... which would do nicely actually.

CF would be equally cool.

	Johnny

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