Steve's MV/2500
Here is the story of my MV/2500DC and its protracted resurrection.
Getting the Mini
In January 2013 a saved search that I’d had running for years on eBay finally came up with something interesting. The seller’s description read…
Data General MV/2500. Unfortunately has to be sold for spares or repair - it was powering on okay while I was testing prior to listing, when it suddenly fell silent and now doesn’t start up any more. There is some power getting through the system - the tape drive and hard drive lights have been lighting up, but the main fans and processor have been silent. Hopefully this is repairable. The system disk may be a little stuck as the computer has been sitting powered off for around 10 years: when the system was being powered, the drive sounded like it was struggling to spin up.
On the 8th January I won the auction.
What Did I Get?
I appear to have got the following…
- MV/2500DC with 24MB RAM, 322MB HDD, another HDD, LAN Controller, 0.5" cartridge drive
- 1 x PHU G-10565 with a double-height 2.3GB 8mm Tape Drive (Exabyte EXB-8200)
- 1 x PHU G-10565 with two HDDs
- 2 x D462 Dasher Terminals
- 1 x AUI to 10-Base 2 tranceiver
- 1 x spare single-height Tandberg TDC 4222 DG QIC tape drive
- 1 x DG branded Serial Distribution Board
- Cables for terminals, distribution board
- Assorted cartridges (listed separately)
- 1 x Manual - ‘Using the CLI (AOS/VS and AOS/VS/II)" - 093-000646-01 At least one of the terminals appears to be working, and the dual HDD PHU appears to start up OK, but the MV/2500 is silent when powered up.
Tapes
Mini-Data Cartridges
There are a number of potentially interesting cartridges in this format - but no drive!
- AOS/VS II - Rev. 3.00 - 1 of 2
- AOS/VS II - Rev. 3.00 - 2 of 2
- AOS/VS ‘C’ - Rev. 4.20
- MV2DC_II/DS75_II SCP System Media - Rev. 10.00, Microcode - Rev. 11.00 - 060-000154-11 - 1991
- Netware Transport for MV/Family - Rev. 2.00 (2 copies)
- TCP/IP II - Rev. 1.30
- XTS II - Rev. 2.30 Along with an unused, sealed cartridge.
QIC Cartridges
- DG/UX 5.4 - Rev. 3.00 (MU02) - This is an update, not the complete product
- AOS/VS II - Rev. 3.00, 3.01, 3.10 - Patches, not the complete product
- XTS - Rev. 2.20, 2.30 - Patches again, not the product
- 7 other 150/525MB Cartridges which appear to be scratch/backups
Dead Disks and Tape Teasers
On January 14th 2013 I tried powering up the PHUs.
Firstly I tried to power up the PHU (Peripheral Housing Unit) containing two disk drives - a double-height and a single-height drive. The single-height drive seemed dead - and it looks as though someone pencilled something to that effect on the front of it at some point. The double-height drive’s LED indicator lit and it repeatedly tried to spin up. Unfortunately after about 4 minutes smoke started to appear and I can see some burnt out resistors on its circuit board. I’m not too disappointed about the HDDs - it’s still fairly easy to source cheap SCSI-II-compatible disks on eBay which I can put into the PHU.
I moved on to the PHU containing the DAT drive. Although the PHU cabinet powered up OK, nothing else happened. I removed the power connector to the drive and checked the voltages which all seemed correct (within 0.5V anyway). Upon reconnecting the power to the drive it sprang into life. As per the manual both LEDs lit while it did its self-check then I was able to operate the eject button and the unit opened properly. On a whim I connected up the loose QIC drive that came with the system - it seems to start-up too. So I installed the QIC drive into the same PHU as the DAT drive - henceforth refered to as the ‘tape PHU’ :-)
Trying Out a Terminal
I connected up one of the D462s to my PC via a null modem cable and, after quite some fiddling with baud rates, parity, line control and stop bits (this turned out to be the key) I got it talking to Ubuntu running in a virtual machine on a Windows 7 host.
Once I had installed terminfo on the Ubuntu box I was able to set the terminal type to d462-dg and get some ncurses application to run reasonably as you can see.
Not Looking Good
February 11th, 2013: The MV/2500 is now disassembled andthe PSU is away for repair. It seems that both the internal Micropolis disks have seized and that is probably what killed the power supply.
The prognosis is a bit grim at the moment; I only have the microcode on the dead disks (presumably) and on a Mini Data Cartridge for which I have no drive. So even if the PSU is repaired I’m not quite sure how I will get things working.
One Step Forward…
March 27th, 2013: Yesterday the PSU came back from a friendly technician and, after some fiddling, I got the beast to fire up.
Unfortunately - and as expected - there appears to be a serious issue with the disks. This is what I see on start-up:
In case you can’t read that it says:
Model # 8932; System Processing Unit (SPU) AB, FAILED; ERROR 6:252:74
I know that Break (CMD-ESC) will take me into some sort of primitive boot environment but I have no documentation (or knowledge) of available commands etc.
Next steps:
- Try to get the MV/2500 system media on 130MB CTD format
- Try to get low-level documentation on the MV/2500
- Find out how to attach a PHU to the MV/2500 (no, it’s not obvious!)
- Find out for certain if I can put non-DG SCSI disks in the MV/2500. The two disks in there appear to have DG-originated firmware…
Microcode Diagnostics Running
June 7th, 2013: Some small progress.
For the past week or so I have been trying to image the faulty system disk using a Linux system and the clever ddrescue program. After getting about 20% of the contents off the disk I hit a brick wall, so I did some rather unconventional things to the disk with a large screwdriver and, suddenly it would read OK! I got all except two sectors off the disk and have saved that image.
More in hope than expectation I put the disk back in the MV/2500 and gave it a go. Surprise, surprise it now loads the microcode. There was a parity error showing up on the extended memory, so I had to remove that - down to 8MB now.
Defeatism and a Good Samaritan
On July 15th 2013 I posted the following (on the previous version of this site):
Well it seems that, for the moment, DG’s famous ‘lock-in’ has locked me out of my MV/2500.
Even though I eventually obtained dumps of the system media for the MV/2500 it has proved impossible to use them.
It seems DG used some proprietary format when writing system tapes that prevents one creating a tape in say, Linux, then booting an MV DC with it.
I think I’ve got to the point now where it’ll have to be mothballed until I can either use another MV/2500 to rebuild the disk, or get the system media on 130MB cartridge. Both options seem pretty unlikely at this point.
This post garnered a response some time later…
CTD 130 AOS/VS 7.70 Mod 31133 Created: Jan 11, 2015 Author Name: Mario Vosschmidt I have two tapes labelled as in the subject line. Rescued with most of the remainder of a DG branch office in Germany, tape library saved on CDs, print documentation, micro fiches - the whole lot. willing to send the two AOS/VS cartridges to you, so you might try to reinstall your sytstem. Please let me know.
Of course, I was directly in touch with Mario and then he kindly sent me the first two (of several) cartridges.
On January 23rd 2015 a pair of original AOS/VS 7.70 install cartridges arrived!
It’s the first time in many years I’ve physically handled one of these bespoke(?) DG cartridges - they are a slightly different configuration to any of the more well-known DECtape or IBM cartridges; I will attempt to document the details somewhere on this site.
Anyway, the first install tape loads - so now I know my cartridge drive works - but unfortunately upon trying to run FIXUP the disk failed with a harware error.
I am now exploring options for replacing the disk…
See [[hardware:mv2500sysdiskreplacement|Replacing the MV/2500DC System Disk]] for details.
Disk Replacement Success, AOS/VS Running!
February 16th 2015: I have replaced the (now dead) disk in my MV/2500 with an SD card based SCSI disk emulator board.
I had been following Michael McMaster’s SCSI2SD project for some time when a couple of months ago I contacted him to discuss the feasibility of using SCSI2SD to replace the “vendorized” SCSI-I disks in my MV/2500.
Michael was very encouraging so I placed an order for a fully constructed board and waited for it to arrive from the other side of the world.
In the meantime, Mario from Germany located another couple of tape cartridges which he thought might be useful - diagnostic microcode and ADEX.
After trying the SCSI2SD card on my PC test rig I connected it to the MV/2500. Then followed a short iterative process during which I captured the SCSI activity on startup failure and Michael sent new firmware to address unimplemented SCSI commands in the SCSI2SD firmware.
On the 12th February 2015 I was finally able to boot up the MV/2500 and install and run AOS/VS!
At the moment I still have to load the microcode from tape - it will not install; I think that is because it is diagnostic microcode, not the standard SCP/System Media distribution, or maybe there is a special procedure for DC-class machines. Once that is done the system runs normally - except a little more quietly and using somewhat less power than it would with original full-height 5.25 inch SCSI disks.
I have connected up the serial distribution panel and multi-user AOS/VS 7.70 will now run happily.