20 Nov
1999
20 Nov
'99
2:33 p.m.
Well, with the aid of the "PDP-8/e Simulator" for the Mac, I figured out
how to use the front panel, and execute the "Initial Operating Check".
Load it into the real PDP-8/m, and start it. Wait a minute, that's not
what it's supposed to be doing...
After a bunch of investigating, and going back to the "PDP-8/e Simulator"
to figure out how to display the contents of memory, I discover that there
is nothing in memory :^(
Based on the fact I can see what I'm trying to enter when I've got the
switch set to 'MD' and hit Deposit, it sounds to me, suspiciously like I've
got a bad 4K Core set.
Anyone have any suggestions on something to check?
Zane
| Zane H. Healy | UNIX Systems Adminstrator |
| healyzh(a)aracnet.com (primary) | Linux Enthusiast |
| healyzh(a)holonet.net (alternate) | Classic Computer Collector |
+----------------------------------+----------------------------+
| Empire of the Petal Throne and Traveller Role Playing, |
| and Zane's Computer Museum. |
| http://www.aracnet.com/~healyzh/ |
20 Nov
20 Nov
3:20 p.m.
Try this:
Set all switches to 0, Halt is down, key is set to power ON,
rotary switch to MD.
Press CLEAR
Press Extd Addr Load
Set the switches to 200 octal
Press Addr Load.
Now flip the switches back to 0
press Deposit
set the switches to 1
press deposit
set the switches to 2
press deposit
... repeat until you get to 10 octal...
Now set the switches to 0200 octal
press ADDR LOAD
press EXAMINE
Data LEDs should show 0
press EXAMINE
Data LEDs should show 1
If they do, you are reading back memory and writing it. If they don't you
have a problem.
The first thing to check is that all the top connectors are in fact on.
There should be no "edge" connectors visibla at the top.
The next thing to check is the first board in the MEMORY stack has three
solder jumpers in the lower right hand corner. They should _all_ be
soldered in. (that's three 0's or page 0)
The next thing you should check is that the back plane does _not_ have gunk
in it. This is a very common fault on old 8's.
--Chuck
At 08:33 PM 11/20/99 -0800, you wrote:
Well, with the aid of the "PDP-8/e Simulator"
for the Mac, I figured out
how to use the front panel, and execute the "Initial Operating Check".
Load it into the real PDP-8/m, and start it. Wait a minute, that's not
what it's supposed to be doing...
After a bunch of investigating, and going back to the "PDP-8/e Simulator"
to figure out how to display the contents of memory, I discover that there
is nothing in memory :^(
Based on the fact I can see what I'm trying to enter when I've got the
switch set to 'MD' and hit Deposit, it sounds to me, suspiciously like I've
got a bad 4K Core set.
Anyone have any suggestions on something to check?
Zane
| Zane H. Healy | UNIX Systems Adminstrator |
| healyzh(a)aracnet.com (primary) | Linux Enthusiast |
| healyzh(a)holonet.net (alternate) | Classic Computer Collector |
+----------------------------------+----------------------------+
| Empire of the Petal Throne and Traveller Role Playing, |
| and Zane's Computer Museum. |
| http://www.aracnet.com/~healyzh/ |
5:54 p.m.
If they do, you are reading back memory and writing it.
If they don't you
have a problem.
They don't :^(
The first thing to check is that all the top connectors
are in fact on.
There should be no "edge" connectors visibla at the top.
Done.
The next thing to check is the first board in the
MEMORY stack has three
solder jumpers in the lower right hand corner. They should _all_ be
soldered in. (that's three 0's or page 0)
Dang, I thought you had it for a minute, the wires aren't where you'd
expect them, but they are in fact in place
The next thing you should check is that the back plane
does _not_ have gunk
in it. This is a very common fault on old 8's.
I'm afriad this was the first thing I checked out, included removing the
pine needle. Earlier to day, I stripped the system down, cleaned it up,
and put it back together following the maintenance manual on how it should
go together.
Been looking through the maintenance manual, and it looks like among the
things I need to do tomorrow to check this out is to test voltages on both
the G104 and G227 boards. This has me wondering, does it matter if the
order is G104/H220/G227, or can you order it like G227/H220/G104 for
testing so you can take readings on the G227 board?
Also, just looked at Highgate, I take it the printset for a 4K Core Stack
isn't available online anywhere?
Zane
| Zane H. Healy | UNIX Systems Adminstrator |
| healyzh(a)aracnet.com (primary) | Linux Enthusiast |
| healyzh(a)holonet.net (alternate) | Classic Computer Collector |
+----------------------------------+----------------------------+
| Empire of the Petal Throne and Traveller Role Playing, |
| and Zane's Computer Museum. |
| http://www.aracnet.com/~healyzh/ |
9:33 p.m.
New subject: DataIO 212 tips?
I picked up a DATAIO 212 today, and apparently DataIO has no online support
for "obsolete" hardware. Anybody have some tips on basic operation? (I know
I need to ID the "module" that came with it, but ...)
11:03 p.m.
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21 Nov
21 Nov
5:52 a.m.
[PDP8/m with core problems]
That was kind of obvious, and thanks to a pretty good picture in the
maintenance manual I was able to verify how I was supposed to have
connector blocks on stuff in the system. Thankfully I had all of them.
The first thing to check is that all the top
connectors are in fact on.
There should be no "edge" connectors visibla at the top.
In the core memory set, sure (you need 4 top connectors here -- 2 to link
to the core stack to each of the other 2 boards). But there will be open edge connectors on the top of the CPU set -- you can
insert the EAE card
set between the CPU boards and the clock generators, and it has top
connectors to both the CPU and the clock.
IIRC, without the EAE, there's nothing on the top connectors of the M8330
clock, and 1 top connector between the 2 CPU boards (maybe 2 -- whereever
there are 2 connectors aligned on the 2 CPU boards).
Looks like the EAE would have one connector to the Clock, and one to the
CPU board set.
Worth cleaning the top connectors as well...
I cleaned them, but it might not have been good enough. I ended up using
rubbing alcohol to clean all the contacts on the boards.
Been looking
through the maintenance manual, and it looks like among the
things I need to do tomorrow to check this out is to test voltages on both
the G104 and G227 boards. This has me wondering, does it matter if the
Do you have a 'scope? This is the sort of problem where I'd start by
checking a few waveforms. Check to see if the CPU appears to be writing
data to memory. Check to see what the address decoder and XY drivers are
doing.
20 Nov
20 Nov
10:55 p.m.
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