On 2017-10-05 12:57 PM, Guy Sotomayor Jr via cctalk wrote:
On Oct 5, 2017, at 2:53 AM, Christian Corti via cctalk <cctalk@classiccmp.org>
wrote:
On Wed, 4 Oct 2017, Guy Sotomayor Jr wrote:
Also, the early desktop PS/2 (model 50 and such) had the controller integrated
on the drive and those were Maxtor as I recall. The PS/2 shipped in 1987 and
we had the drives in labs at least 12-18 months prior (memory is dim on this
right now).
No. The IBM 8550 has the controller on a special card and the drive had a PCB
edge that inserted into the PCB connector on the side of the controller. The
8550-021 used a 20MB IBM WD-325N disk drive (P/N 90X6806). The controller is a
ST-506 type MFM controller (with DMA, so it rocks with a sustained data rate of
above 500kB/s!). My father upgraded the system with a standard Rhodime 50MB MFM
drive. There was a purely passive adapter that split the card edge connector
into the normal 20+34 pin connectors plus power. I still have that system and
drive :-)
OK, my recollection must be faulty since I thought that the “riser” was passive
e.g. just some connectors for HDD and floppy, traces and plugged into the
motherboard.
There were a number of different drives. I don’t recall the 20MB drive. I
mostly saw 60MB and 120MB drives.
TTFN - Guy
It would appear that the original 50 was shipped with a ST506 disk drive
that would seem to have been connected to microchannel adapter card.
The 50Z is described as coming with an ESDI drive, and from the pictures
I have seen the drive plug into an adapter card that is in turn plugged
into a reserved slot on the system board that may be a regular
microchannel slot, but was reserved because the drive plugged directly
into a connector on the card. This card does have logic and EPROMs on
it so is more that a simple riser, the drive however does not have
standard ESDI connectors on it and does resemble the DBA drives. The
model 70 that is in a case very similar to 50 and 50Z has what is called
Direct Bus Attach (DBA) drives with a riser from the system board that
provides connectors for the DBA disk and diskette drives. The model 70
tech ref manual shows the connector for the DBA drive as being on the
microchannel bus. I do remember seeing 50s and 70s, but most of the
PS/2s I saw when doing machine room support where 60s and 80s.
Paul.
Paul.
