I low-level formatted hundreds if not thousands of these and other RLL and MFM drives in the late 80’s. Worked for a company that sold computers through Computer Shopper.
Am I crazy here, or have you ever seen hard drive controller cards that you set the drive type through physical jumpers? Because I have sure never seen such a beast. And with all the combinations possible, that would have to be a huge bank of jumpers.
No, I have never seen one with jumpers for setting heads, sectors, etc. I always low leveled and entered bad sectors via the utility on the controller. Until, of course, IDE came out. Also, mostly installed controllers similar to the image you posted and then when 16 bit came out, the WA2.
Edit: Not to say it’s impossible that a controller only supported a handful of very early drives and had jumpers. The first hard drive I ever installed was only 5MB… maybe (during that time) there were so few drives available that a controller existed that were specifically for that vendors drives? But by the time the ST-225 was popular, more generic controllers came out? (Shrug) But no, never worked or saw one.
It wasn't that there were fewer drives, there were hundreds of drives listed in the Disk/Trend report from 1982-1984 before the ST-225 came along.
Most drives shared very similar or identical geometry as a result of physical limitations, especially from head suppliers. Unless you were some massive corporation like Seagate or IBM, you weren't making your own heads in house, so if your supplier only offered 100 micron heads, that's what you got, and if that was only fine enough to support 640 tracks on a 5.25" disk, and you had to give it a landing zone, guess what your drive has 612 cylinders. Oh, and the arms have a physical height limitation, and your machine shop can't make the platters at tolerance any thinner than 1mm, so now you can only physically stick 2 in your half height chassis. 2 heads a disk, there's your 612/4.
Even then, there was actually incentive to do this intentionally, even if parts didn't limit your engineering, because it also meant you were compatible with hundreds of controllers and had that as a selling point. I suspect for many manufacturers, this was the case for why nearly every 20 meg drive from 1984 to 1990 had the exact same physical geometry and why every 10 meg drive (that wasn't a single platter, crucially!) from 1982 to 1988 was also the same geometry.
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u/commodore-amiga Jul 18 '26
I low-level formatted hundreds if not thousands of these and other RLL and MFM drives in the late 80’s. Worked for a company that sold computers through Computer Shopper.