24 Feb
2021
24 Feb
'21
8:12 a.m.
On 2021-02-24 11:06 a.m., Jon Elson via cctalk wrote:
On 02/24/2021 08:06 AM, Chris Zach via cctalk wrote:
Well, just the guts inside an RM05, that was a
9762 drive relabeled by
DEC.
Actually the RM05 was a 9766 - the 9762 was an RM03 when DEC re-packaged it
Sort of. MASSBUS was a very overpriced and to be honest weird system
that DEC developed in an attempt to be like IBM and charge very high
markups for generic peripherals. While it did support a variety of
interface formats (I don't think the RS03 and 04 were SMD, and I know
the RP07 was *not* SMD) the industry quickly centered on SMD and that
was that.
OOOOhhh, the RP07!? I have stories about that drive!
It was a Burroughs mainframe drive they reprogrammed for DEC.? It had
a number of issues.
The worst one was that due to some microcode bugs, it was possible to
trash an occasional track descriptor record.? When a bad TDR was read,
the drive totally locked up, you had to cycle power to reset it.? VMS
recovered from it quite gracefully, however.? They finally fixed it,
it required replacing about 10 boards.? Then, there was a procedure to
rewrite all the TDRs.? The DEC FE assured me it would not touch user
data.? Well, after running the procedure, it came up as a blank disk!?
YIKES!? A quick check at the binary level showed data was still on the
drive, but the RMS-11 home block had been overwritten.? Well, I had a
program that could examine the home blocks, and I knew where to find
the backup home blocks.? So, I hacked that program to copy the backup
block to the main one, and then change the checksums to agree.
The other issue is the voice coil could suck dirty air in during long
seeks, so they had ti replace the HDA and put a filter over the air
exhaust from the voice coil.
Yes, the TM02 and TM03 formatters allowed MASSBUS
to connect to
Pertec drives, but I don't think you could run a tape drive and a
disk drive on the same MASSBUS channel anyway. Wonder why,
technically the MASSBUS cable is just an extension of the Unibus, so
it shouldn't matter much what combination of cables you used. Maybe
they just wrote different drivers or something.
MASSBUS was not anything like a UNIBUS, it was a lot closer to an IBM
channel bus and tag cable.
Anybody
knows if there was conversion kit to equip CDC 9762 and 9766
type SMD drives into MASSBUS drives much like the TU81 could be
turned into a TA81 (SDI)?
Jon