NCR model 3401 class 5451

From: R. D. Davis <>
Date: Tue Jun 20 23:10:58 2000

Tonight, I did some more checking into the following system:

On Sun, 18 Jun 2000, R. D. Davis wrote:
> Greetings, is anyone here familiar with an NCR model 3401, class 5451
> "application processor"? On a hand-written label on the front of the
> machine there's a description of the memory in it: 8MB, 145ns. This
> box has the following switches on the front panel, in addition to the
> power switch:
> Station ID (two thumbwheels)

Does this indicate that this was part of a multiple-processor system?

> Load options:
> local/aux
> disk/tape
> primary OS/alt OS

Does anyone on this list know of other systems with a switch that
apparently selects which operating system gets loaded?

> BCD restart/system reset

Does anyone have an idea what BCD restart is? It causes the
diagnostic display to blink. System reset causes it to go through the
same countdown that occurs when the system is powered up, then as also
when powered up, displays a few different codes, then displays 800F.

> diag port: on/off
> mode: normal/diagnostic
> ps margin: +5%/normal/-5%

What's a ps margin switch for?

> On the back of the machine are the following connectors:
> LS link (low speed link?): pos 0, pos1, pos2 (9-pin)
> Diagostic port (25-pin - RS232 port?)
> System bus: channel A, channel B (9-pin)
> HS link (high speed linl?): pos 4, pos 5, pos6, pos7 (9-pin)

The boards in this system include:

* NMAB board (does anyone have an idea what this is?):

Contains mostly 74xxx logic, including about 30 or so 74F374 ICs,
74F244, 74F139, 74F373, 74F191, 74F175, etc., and some Motorola ICs:
6-1090367DS and 7-1682604DS (no idea what these are). Also some PCA
EP8301 active delay lines. There are three wide ribbon connectors
(approx. 50 cond.) going to both the memory and CPU boards, and a
fourth that just goes to the CPU board.

* Single Port Memory Mother bd.:

This contains eight memory cards, and has another 8 empty slots, so, the
maximum memory this system can use, I'm guessing, is 16MB.

* PE API (main part of CPU board):

Contains six 1" square chips with heat-sinks I can't remove to see the
IC ID numbers. I was told this system has some Intel chips in it,
and, not seeing any elsewhere, am guessing that these are the Intel
chips. What Intel chips co-exist with a writeable control store?
Can't wait until the schematics arrive!

There are also sixteen little square block ICs: PCA EP7308 077-8337305
(no idea what these are - couldn't find any info. Delay lines?) and
four larger 24-pin (IIRC) chips: NCR/32-5802E 6266155 7-1680941 and
NCR/32-590F C906A21 7-1680951 (does anyone know what these are?), two
crytal oscillators (13 and 32MHz), etc.

* Writeable Control Store:

Mounted atop the CPU board. Contains seventy-two AMD 7-168436 (the
only other number on them is the 86xx date code number) ICs, six
MB7142H (2k * 8 dual port SRAM?) ICs, assorted 74Fxxx logic, six
Motorola 7-1682609DS, etc. Somehow, I'm getting the feeling that
the numbers on some of these chips are special numbering schemes
from NCR, e.g. the 7-xxxxx... numbers. :-(

* SBA/TOD - appears to contain the time of day clock circuitry; anyone
know what SBA stands for? This is also mounted atop the CPU board.

* API/SAM - very small circuit board containing two 555 timers and a few
other ICs; this board is mounted atop the SBA/TOD board.

R. D. Davis             
Received on Tue Jun 20 2000 - 23:10:58 BST

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