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Bare Card Cage #2

(last updated: 21-Sep-2008)

Nickname: "Nekid Two"
Model: n/a
Serial No: unknown
Enclosure: n/a
Mfg date: ??

Operational Status

Not operational...
...CPU board not working, but I have confirmed that the CPU chipset is all good, so something on the board itself.

Configuration

The current configuration is in its original 'as acquired' condition.

Software
n/a

Hardware

Backplane / Modules

H9270		A	C
Q18/Q18	1	M7264-AB : KD11-F : LSI-11 CPU w/ 4KW RAM
	2	M7940 : DLV11 : Serial Line Unit	(empty)
	3	(empty)	(empty)
	4	(empty)	(empty)

Mass storage

none

Needed or Missing Items
none

Major Events

20-Feb-2006 - Acquisition
12-Mar-2006 - Cleanup
04-Oct-2006 - Operational testing
09-Aug-2007 - Operational testing (cont.)

Still To Do

locate suitable power supply
test functionality

Description

Acquisition

20-Feb-2006

This unit was part of a large pickup in Longmont, Colorado.

Cleanup

12-Mar-2006

I removed the cards, vacuumed each one, photo'd each one, and then the backplane.

The M7264 has the word 'BAD' written on the solder side of the handle. The M7940 has 'No! XTAL OSC / No! 12V' labeled on it.

I reinserted the cards and re-wrapped the backplane in foil.

The boards were photographed in sequence.

Operational testing

04-Oct-2006

Using the known-working DLV11 from the Longmont Bare Cage #1 connected to the LA36 DECwriter, I tried this CPU out. I attached the Sigma Information Systems power supply to the backplane and fired it up.

No output. Hmm. Same as Bare Cage #1. I wonder if both of these systems were given to Dworkin in the first place because they were already bad. In fact there is a small handwritten notation on the underside of this CPU board's handle rail with "BAD". It could be that it really is bad. I don't know. Perhaps some time with the oscilloscope would help, but I'd need more technical information on this M7264 CPU board before I try that.

Operational testing (cont.)

09-Aug-2007

With recent success with *all* other systems from Longmont, I turned my attention back to this minimalist system. I wanted to see if the CPU board worked at all, first.

I installed the board in my LAB DATAX backplane, along with the DATAX DLV11-J. This eliminated all variables except the CPU board. The chassis, power and backplane, and the DLV11-J, are known to be good. All that's left is the CPU board.

Same result as last fall. Nothing seen on the console. The CPU is not working. The board includes all four chips, just like the LSI-11/2 board, and perhaps, again like the H11A 2-switch, there is a bad IC in the CPU chipset.

First, I pulled the board from the Bare Cage #1, and confirmed that it works. Now I have an identical board to swap with. In the end, after swapping each of the CPU chips, I confirmed that the chips are good...something on the board is bad.

Comparing the two boards, the only visible difference is the the #1 board has the W3 jumper closed, where this boards was not. I installed that W3 jumper (disable LTC interrupt) and tried again. Still no luck. I get nothing from the board.

M7264 (etch rev E) : LSI-11 CPU w/ 8KB (4KW) RAM : s/n 1325214
	- Resident memory bank 0 (0-4K) selected
	- External LTC ***disabled***
	- Memory refresh enabled
	- Power-up mode 1 (ODT) selected
	- Resident memory reply enabled
	- Resident memory reply during refresh enabled
	- On-board memory select enabled

BTW, this might be relevant: also in the DATAX is the Alloy LSI-50 board, really just to put a load on the backplane. But, in the past, I have observed the red LED on that board and generally see that it might be lit upon power up, but with a flip of the RESTART switch, which I think initializes all the boards, this LED will go out. However, now with this Bare Cage #2's CPU board, I can toggle RESTART many times, but never see this LED go out. So something on the CPU board is not letting the proper reset signals pass to the bus. Something to consider, anyway.

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