20 Jun
2015
20 Jun
'15
10:40 a.m.
I am looking for any information on a National Semiconductor RAM board that I think goes
in
a VAX 11/730. My 11/730 (which admittedly I have not run) has 2 DEC MS730 boards and 2 of
these
NatSemi boards, I found another one while unpacking stuff today.
It's a hex height DEC-type board with the ejector handles. Connections to fingers on A
and B as you
might expect, also the grant continuity strapping on C and D, grounds on D (only) and a
couple of signals
on C (I've not figured out what yet).
The only identification I can find on it is in the etch :
PWB 551109464-002 B
PWA 980109464
(I assume the first is the part number for the bare PCB, the second for the stuffed
board)
There seems to be one RAM too many!. The main RAM array is 4 rows each of 32 4164-like
DRAMs.
There is a second block of 28 such DRAMs, presumably 7 bits for each row of the main array
to
provide the ECC bits. And then a further single RAM off to one side. The DEC MS730
doesn't seem
to have this, and I wonder what on earth it is for.
Rest of the board is TTL drivers, etc. There are 2 LEDs, one green, one yellow. And a
momentary pushbutton
switch. I have no idea of the functions of those.
Does anyone recognise this board?
A related point, I am thinking of removing the TSU05 from my 11/730 and putting an
expansion
box in place of the tape drive in the rack. In which case I can install this memory board.
Is 5MBytes
(the maximum an 11/730 can take) worth having over 4MBytes?
-tony
20 Jun
20 Jun
10:58 a.m.
[Argh! Following up my own post :-(]
I am looking for any information on a National
Semiconductor RAM board that I think goes in
a VAX 11/730. My 11/730 (which admittedly I have not run) has 2 DEC MS730 boards and 2 of
these
NatSemi boards, I found another one while unpacking stuff today.
[...]
The only identification I can find on it is in the
etch :
PWB 551109464-002 B
PWA 980109464
[...]
There seems to be one RAM too many!. The main RAM
array is 4 rows each of 32 4164-like DRAMs.
Rest of the board is TTL drivers, etc. There are 2
LEDs, one green, one yellow. And a momentary pushbutton
switch. I have no idea of the functions of those.
That switch may well be latching (alternate action). I wasnt't pressing it hard
enough. It seems to be
wired directly to the yellow LED (amongst other things).
I have found a mention of this board in an 11/750 FAQ (not surprising, I think the same 1M
boards can
be used in the 11/750 and 11/730). It appears that in normal operation both LEDs are on.
Pressing the
button turns off the yellow LED and completely disables the board. Quite why you'd
want to do this I do
not know...
Oh, and it mentions a 'spare RAM chip in a socket on the board'. All RAM on my
board is, indeed, socketed.
If this is just an unused chip to substitute if one fails then I think I've seen it
all...
-tony
11:13 a.m.
On Jun 20, 2015, at 07:58, tony duell <ard at
p850ug1.demon.co.uk> wrote:
Oh, and it mentions a 'spare RAM chip in a socket on the board'. All RAM on my
board is, indeed, socketed.
If this is just an unused chip to substitute if one fails then I think I've seen it
all...
I thought of throwing that idea out there, but having lived through the great RAM famine
the thought of a spare RAM chip seemed kind of silly. Incidentally, the RAMs are all
soldered on my Camintonn boards.
--
Mark J. Blair, NF6X <nf6x at nf6x.net>
http://www.nf6x.net/
1:37 p.m.
I thought of throwing that idea out there, but having lived through the great RAM famine
the thought of a spare
RAM chip seemed kind of silly. Incidentally, the RAMs are all soldered on my Camintonn
boards.
All the RAMs (but not the buffers) on the NatSemi boards are in sockets. And I am not sure
this is a
Good Thing, they are not good quality sockets at all. They're the very cheap ones that
make contact with
one side of the IC pin only. But replacing the lot with turned pin is something I will
only do if I start having
RAM problems on those boards.
I've done a little buzzing out with an ohmmeter :
The green LED + a 270R resistor are across the 5V line (which is presumably the battery
backed memory
supply line. if you have that optio). I assume this indicates the board is powered up.
The moving contact of the switch is grounded.
One of the other contacts of the switch goes to the yellow LED + 270R to +5V. So as
suggested, the yellow
LED indicates the state of the switch.
The other contact goes into the logic. I've not traced it all out yet, but it would
appear to disable many of
the buffers when it is low (i.e. when the yellow LED is off). So the idea that the yellow
LED is on for normal
operation and the switch can turn it off and disable the board makes a lot of sense.
That 'extra' RAM gets power, but nothing else. As far as I can tell none of the
other pins go anywhere. Isn't
that a bad idea, to have a MOS device with all inputs floating? I would have thought it
would have been
better to tie eveything (including the +5V pin) to ground, or to power the RAM but have
pull-up resistors
on all the inputs.
-tony
21 Jun
21 Jun
12:32 p.m.
On Sat, Jun 20, 2015 at 10:58 AM, tony duell <ard at p850ug1.demon.co.uk> wrote:
> I am looking for any information on a National
Semiconductor RAM board that I think goes in
> a VAX 11/730.
Pressing the
button turns off the yellow LED and completely disables the board. Quite why you'd
want to do this I do
not know...
The reason you'd want a button to disable the board is when running
diagnostics, you can "remove all the non-DEC memory" without
physically removing it. Of course it still could be the source of a
problem, but at least operational memory boards can be "deleted" so
they don't grossly affect the diagnostic code.
It's a "feature" to allow customers to buy less-expensive RAM and
still have a way to pass diagnostics without fingerpointing from DEC
about that "other" board in there.
-ethan
1:08 p.m.
Pressing the
button turns off the yellow LED and completely disables the board. Quite why you'd
want to do this I do
not know...
The reason you'd want a button to disable the board is when running
diagnostics, you can "remove all the non-DEC memory" without
physically removing it. Of course it still could be the source of a
problem, but at least operational memory boards can be "deleted" so
they don't grossly affect the diagnostic code.
It's a "feature" to allow customers to buy less-expensive RAM and
still have a way to pass diagnostics without fingerpointing from DEC
about that "other" board in there.
20 Jun
20 Jun
11:11 a.m.
On Jun 20, 2015, at 07:40, tony duell <ard at
p850ug1.demon.co.uk> wrote:
Does anyone recognise this board?
I don't recognize that board, but I thought I'd point out the non-DEC memory in my
730. It uses Camintonn CMX-750 memory boards, and I have a CMX-750/730 installation manual
that I can scan. I plan to scan it for Bitsavers and Archive.org anyway, but it can jump
higher in the queue if anybody has an acute need for it. I pulled one board out of my
machine to look at it, and it does not appear to have that oddball extra RAM chip. It has
a red paddle type toggle switch and an LED.
A related point, I am thinking of removing the TSU05 from my 11/730 and putting an
expansion
box in place of the tape drive in the rack. In which case I can install this memory
board. Is 5MBytes
(the maximum an 11/730 can take) worth having over 4MBytes?
In my system, the M9302 bus terminator (dual) and M7454 TU80K (quad) are in the same row.
Would this imply that I could replace the M9302 with a BC11 cable to add an expansion
cabinet without losing any of the functions already installed in the CPU cabinet? And if
so, maybe Tony's system could also grow an expansion cabinet without losing the TSU05
card?
--
Mark J. Blair, NF6X <nf6x at nf6x.net>
http://www.nf6x.net/
12:16 p.m.
In my system, the M9302 bus terminator (dual) and M7454 TU80K (quad) are in the same row.
Would this imply
that I could replace the M9302 with a BC11 cable to add an expansion cabinet without
losing any of the functions
Yes, you can. The M9302 is in a 'Unibus Out', you can plug a Unibus cable in there
to link to an expansion
box. The official way (as I think I mentioned the other day) involved special dual-height
cards at each end
with 3 40-way Berg-type cables linking them. But the cards were just connectors, not even
buffer chips.
It being easier to route 40 way ribon cables through the cable pan rather than a BC11A...
already installed in the CPU cabinet? And if so, maybe
Tony's system could also grow an expansion cabinet
without losing the TSU05 card?
It could, other than the fact that I would like to keep it in the half-rack, so I would
have to remove the TS05
drive to have somewhere to fit the expanison box. In any case the TSU05 could go in said
expansion box if
I ever need it, I think.
My TS05 needs a bit of work to get it going, and I do wonder how useful it would be. Any
comments?
-tony
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days inactive
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