Our MicroVAX II is actually a MicroVAX 4000-200 as identified by its KA660 installed boards - shown in the upright enclosure to the hard right of the below image.
The SHOW VERSION command provides the following KA660 version
On the side of the enclosure appears several internal asset tags.
Originally installed were
Slot
1 - KA660 CPU
2 - MS650-BA MEM 16MB 1989
3 - MS650-BA MEM 16MB 1989
4.0 - M3xxx Asynchronous Dual Serial card with two rear housing headers
4.2 - Emulex SCSI card
5 - TQK70 - Controller card
There was no DSSI Cable connecting the DSSI bus to the CPU board. The CPU boards DSSI connector is piggybacked to the memory controlled connector.
During restoration we found
- Memory in slot 2 had 1024 bad pages
- Memory in slot 3 had 4096 bad pages
- The TK70 doesn’t enumerate on the bus
- The unit attempts to boot from EZA0 Ethernet as standard.
- The unit has an external 50 pin centronics style SCSI connector
Prototype
The MicroVAX 4000 series originally shipped in a BA215 or BA430 case in 1991~
Our unit is installed in a MicroVAX II housing
The memory date code suggest the two installed 16MB boards are from 1989 and predate the MicroVaxs release.
The digital internal asset codes and the fact these units came from Max Burnetts BACK Museum probably indicate this was an internal test unit or upgraded VAXII modified to run in a non standard enclosure.
Documentation I’ve read doesn’t seem to show images where the DSSI is piggybacking the memory 50 pin interface- however I believe this is normal. (This is NORMAL - earlier block diagrams don’t show it well)
Learnings
The MicroVAX 4000-200 supports a maximum of 64mb of ram in 4 x16 mb cards.
The MicroVax 4000-200 need to have two memory cards installed (or at least one with a free slot) to pass diagnostics boot
The MV4-2 has onboard DSSI, Ethernet and console all on its main board which includes its memory controller. The memory controlled connects via a 3/4/5 header 50 ping ribbon to the 2/3/4 ram boards installed directly below it.
There is no RAM on the CPU
The RTC clock battery is located on the rear Console and diagnostic panel.
More info can be read hereKA660-A Digital manual
Faults Addressed to date
- The 4096 bad page card has been replaced with a MS650-BC new card which is a dual control 32MB ram board that reports to the system as 2 16MB cards on one Q22 slot.
- We located and connected a SCSI RA90? That boots VMS 6.3
- The installed TK-70 tape drive has been cleaned and serviced
Notes 29/4/23
We found a new 32MB 7922-C7 to replace two defective 16MB 7922-A7s in our Micro VAX 4000-200.
We have now found VMS 6.2 on an old SCSI drive that boots now (no kernel panic - thanks new ram!** scratch that- the serial card was doing it**) and it’s from a VAX3100 based on the name! Next step is breaking into a super user - This ended up being achieved easily thanks to Facebook DEC Alumni Michael Ross who directed us here → Resetting a password for SYSTEM account in VAX/VMS · GitHub
The username is now SYSTEM (original) and PASSWORD - is written on the top of the physical drive.
Outstanding Issues
- Memory board in slot 3 has 1024 bad pages and needs to be repaired
- TK70 isn’t visible on the M7559 - doesn’t enumerate. Need to try CONFIGURE command to see if it resolves.
- Installed M3017??? 8 port asynchronous Serial card is causing kernel panics when booting to installed in VMS
- Battery needs to be replaced or removed
