[HECnet] PDP-11/70 on FPGA

[Johnny Billquist]

Brian Hechinger wrote:
On Tue, Aug 10, 2010 at 06:50:32AM -0400, Paul Koning wrote:
http://opencores.org/project,w11
Think that can run RSX/RSTS?
I'll have to take a look... a second reason to get an FPGA eval board...
It only runs on two boards, but at $100 for one, it's not a bad price, really.

Definitely an attractive price, yes.

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.
I get the feeling that's something he'll be adding.   Does the lack of FPP affect
me currently?   Probably not, but of course it would be nice to have.

Both from reading his information that he has published, and from my discussions with him, I get the impression that this is not high on his list, and might never be. But I might be wrong, which would be nice.

For me, this is definitely something that for means that I'm not interested. But as I said, others may very well have other views. I'm just giving my view on it.

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.
Yes, this I can agree with, most definitely.
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* I've got a UDA50 laying around (or know someone who does), what would
be required to extract the firmware from it?

I really don't see the point. The firmware is located in a bunch of proms. Might be 2732 or something similar, if I remember right. But extracting the data from these will not be much help. You need to remember that the UDA50 is a "computer", so this will be the firmware for that machine. And it's a specific machine for just doing the UDA50. So, in order to have this firmware useful, you would need to implement the same "computer" as the UDA50 is.

Or else decode the machine code of that hardware, so that you then can disassemble the firmware. But what good would that be? The MSCP protocol as such is already known (with a few exceptions), so all this will give in addition is how the UDA50 Unibus interface is implemented, and how the SDI interface works. Neither of which is that useful information either.

I don't think the UDA50 use any common microprocessor even, but is implemented with bitslices, and logic.

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.
Yes, I agree, the backend server bothers me a bit as well.   I've love to have
something I could plug a CF card and an ethernet cable into and be done with
it.

I would not mind a IDE, ATA, or any other kindof common modern interface with small, solid state mass storage. The backend is, in this case, not for me important. Just having one that is common, for which storage is cheap and small would be enough. But unless you go MSCP for the PDP11 side, you'll be talking disks with sizes that are just a fraction of any storage existing today. The absolutely largest non-MSCP storage is the RP07, which is Massbus, and that's still only about 0.5G.

That all being said, I'm sure this guy isn't done and who knows, send him your
suggestions, he might be up for it. :-D

Oh, he definitely don't mind suggestions and opinions. Go ahead and talk with him.

	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