Someone asked this over on the Sinclair group a short while ago, but I
suddenly thought that someone here might know...
Basically they were wondering what the internals of the Z80's instruction
fetch were, given that some instructions are multiple bytes in length, but
there's only a single-byte instruction register.
I theorised that control in the Z80 is all just a state machine, so multiple
instruction bytes presumably advance things to a new state (and what's left in
the IR during execution is just one byte from a multi-byte instruction) - but
it sounds like the OP was wondering if anyone knew the exact mechanism
(basically, has the design of the state machine ever been documented anywhere).
(Given that I'm on a 'homebrew CPU' trip right now, I'm rather curious, too :-)
Quite possibly this level of detail's never been made publicly available, but
I figure someone here may have had close involvement with Zilog and know more.
Online resources cover the overall internal architecture, but just 'black box'
the control logic section (including the IR).
cheers
Jules
I just put up another MicroAngelo S-100 board on the VCGM. Sorry for the
additional "sale" post, but a number of people here were looking for one that
might not check VCGM regularly.
http://marketplace.vintage-computer.com/
I have a SR-51 TI calculator. I don't know if it works. Available
for shipping costs.
I also have a HP-35 with manual, purchase receipt, hard case, and
power supply. It doesn't work with the power supply as is, but I
don't know if the power supply works. Available for shipping costs.
If they aren't worth anything, I can send them to the recycler. I
don't know if there are any useful parts or not.
I also have some little computer/calculator units. They are like the
TRS-80 portable version, except smaller. I'm not sure what I'm going
to do with them.
Reply to the From: address below, not to me - LJW
-------- Forwarded Message --------
From: Cheryl & John Wilkins <wilkins at foxvalley.net>
Reply-To: Cheryl & John Wilkins <wilkins at foxvalley.net>
To: cctalk-owner at classiccmp.org
Subject: AT&T UNIX PC 3B1 Chicago area, northwest
Date: Tue, 6 Jan 2009 12:20:42 -0600
I have an AT&T UNIX PC 3B1 I'd like to get into good hands locally,
northwest Chicago (ee.gg., Schaumburg, Hoffman Estates, Fox River
areas). Indianapolis or Knoxville, TN, are possibilities, but less
preferable.
--
Lawrence Wilkinson lawrence at ljw.me.uk
The IBM 360/30 page http://www.ljw.me.uk/ibm360
"Logical Design of Digital Computers", Montgomery Phister, Jr., (c) 1958, 5th printing
1960. hardback w/cover, 400 pages, good shape.
"Digital Computer Design", Braun, 1963. hardback, 600 pages, good shape.
Shipped from Austin, TX
Both have basics of boolean logic, branch out into more system level issues, have detail
on memory types and issues, circuit level considerations.
Peter Coghlan wrote:
>> A few of you might remember the Jupiter Ace I had that took a 9V spike to
>> the expansion slot -- and my futile attempts at repairing it. It's been well
>> over four years since I sent it to a listmember who offered to repair it, and
>> all attempts to get the board or the spares I sent with it have failed. At
>> this point, I haven't seen hide nor hair of him in months, although he's
>> apparently still updating his website...
>>
>
> Hi Phil,
>
> If you are not going to let us know the identity of the person involved,
> please at least inform the list owner. A lot of people regard membership
> of the list as conferring a degree of trustworthyness and it would be a
> shame if that was damaged.
The person in question is Lee Davison. Specifically, the Lee Davison that
maintains the website <http://themotionstore.com/leeedavison/>.
I sent the Ace motherboard to him in ~2002, complete with about ?7 worth of
stamps and a ready-filled-out Special Delivery sticker. The agreement was,
he'd try and fix it, and if he couldn't fix it (or if I asked for it to be
returned), he'd return it. I'm fully aware that postage prices have increased
over the past few years, and I've offered to pay for them. The last time I
heard from Lee was in April 2004; he said he didn't want to send it back
"disassembled, which it is -- very much so".
It can't be in much worse shape than it was when I sent it.. the CPU and RAM
were removed, among other things. IIRC, it was due a full set of new IC
sockets (the CPU socket was certainly well stuffed)...
> Ps: I once repaired a Jupiter Ace for a friend. At the time, I had no idea
> whatsoever how to diagnose the problem. Luckily, the defective RAM chip gave
> itself away by overheating (to the point of burning my finger) and replacing
> it sorted it out.
Yeah, 2114s like doing that...
I was going to build a RAM tester for 2114s at one point, until I realised
that they don't usually fail with any degree of subtlety :)
> I do have a very bad memory so I hope it wasn't me you sent your Ace to :-(
> However, I don't fit the bill as I don't have a website :-)
> Unless I've forgotten about that too...
LOL! :)
Thanks,
--
Phil.
classiccmp at philpem.me.uk
http://www.philpem.me.uk/
For my PC01 the rails can be seen here (third from top). Sounds like the
PC04 rails are similar. They have an added plate to make the
rack attachment stronger since they don't bolt at the back.
http://www.pdp8.net/shows/vcfe08/pics/booth3.shtmlhttp://www.pdp8.net/shows/vcfe08/pics/showing.shtml
Normal rails work fine, my PC04 didn't have any so I used normal ones that
attach both front and back. You can see that in the next picture.
For the TU56 I cheated. I mounted angle iron below it which I can slide it
in on and then bolt at my leisure. The drive has a lip which makes things
a little strange but works pretty well. I used aluminum but that is
messed up by sliding the drive.
http://www.pdp8.net/shows/tcf05/pics/big_stuff.shtml?small
The maintenance manual says how it is supposed to be installed. It has a
a support bracket between the rails the drive rests on. (pg 2-3)
http://www.pdp8online.com/pdp8cgi/query_docs/view.pl?id=27
The 'short' rack is indeed a H950 (H950-AA). The one I have houses
curently my 11/35 config (11/35, RX02, RL02).
I'm considering to converting this rack into a GT40 setup, but I
do miss the keyboard for it (LK40).
Ed
> On Jan 5, 2009, at 5:32 PM, Henk Gooijen wrote:
>>>> Also, the full height PDP family rack was called H960, but what
>>>> was the shorter version called, depicted here:
>>>> http://www.corestore.org/8m-1.jpg
>>
>> If I am not mistaken they are called H950. Come to think of it,
>> in H960 fit *6* 10.5" high units, in an H950 fit *4* 10.5" high
>> units :-) But as said, not 100% sure that they are called H950.
>> Anyway, I would love to get one "H950" here in The Netherlands!
>
> I know those racks; love 'em...I've never been able to find one.
> The guy I mentioned the other day (my childhood PDP mentor who is
> working on an 8/a for a factory) had several when I used to hang out
> at his place, but that was ~1985...they are long gone. I'll ask him
> what the part number was; he may remember.
>
> H950, though...I'm pretty sure that is the part number of the
> large rectangular bracket that the rear door mounts to on the rear of
> an H960. Page 6 of the PDP-8/e Illustrated Parts Breakdown suggests
> this (see item #24, referenced on page 8). I have one of these
> frames in my garage, from one of my racks...if I can find it, I'll
> take a look.
>
> The only thing I'm 100% sure about is that I've seen "H950" on a
> sticker somewhere on one of my 19" racks that looks exactly like an
> H960.
>
> -Dave
>
> --
> Dave McGuire
> Port Charlotte, FL
>
>
>
I am trying to keep a PDP8 computer alive which controls a measurement
system. I have a need for spares for this computer, in particular 16k memory
boards and all other boards. In fact the only parts I am now sure about are
the power supply and backplane.
Any suggestions would be appreciated.
Marek Pawlik
