> On Oct 5, 2017, at 11:26 AM, Paul Berger via cctalk <cctalk@classiccmp.org> > wrote: > > > > 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. >
Yea, most of my work on PS/2’s were on 60s, 70s, 80s and various 95s (as well as the P70 luggable). I don’t recall doing very much (if anything on the 50), so it may in fact have been different. I was also on the team that did the processor card for the 70-486 and the “Spock” and “Tribble” SCSI microchannel cards. TTFN - Guy
