The origin of the phrases ATA and IDE [WAS:RE: formatting MFM drives on a IBM PC]

Paul Berger phb.hfx at
Thu Oct 5 13:26:22 CDT 2017

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 at> 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.


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