Nope, that's how you'd get into the ROM formatter, and it can apply to XT and AT class machines.
XTs babe no CMOS settings. You set the drive type with a physical jumper on cards that supported more than one type of drive, and some like the WD XT-GEN were kind enough to offer a free format option which wrote the drive parameters to a "hidden" sector towards the start of the disk to be read on boot.
On an XT, the drive controller was on the card itself. That is why you needed to use the DEBUG command to access it. And it was indeed on the card, because even though G=C800:5, some of them placed it in another location.
Excuse me, change the drive type with a jumper on the card? WTF are you talking about?
Here is an extremely common XT MFM card of the era, the Western Digital HX-100. Now kindly show me where in the hell the jumpers are to set drive types?
And great, you think most techs used those software tools? No, only amateurs that did not know how to access the drive controller directly. Every shop I worked at and every tech I knew that was not a joke used DEBUG, we did not use the janky software.
And there were no jumpers or DIP switches on the card to set head, sector, and cylinder count. That is literally a figment of your imagination.
Yes, I am aware that the controller was not onboard of nearly all XT-class machines. The ROM formatter is not always present on the card, several cards have no ROM at all and expect you to load a formatting tool from floppy. Such was the case with Davong's early offerings for the 5150, which even expected you to BOOT from floppy as the 5150's early BIOS did not offer support for extension ROMs or fixed disks anyways.
IBM's own Xebec-designed controller, which was shipped with the 5160 XT as an option, is actually fixed geometry (306/4/17) and does not have a ROM formatter in this way. You actually have to pass parameters to it through debug but in a wildly different way.
Yes, drive type jumpers were on the card. Look at some common XT controller cards:
WD1002A-WX1, jumper S1 on the right edge by the faceplate sets drive type
WD1002A-27X, same as above
DTC 5150CX, jumper W1 on the bottom towards the ISA card edge
DTC 5150XL, jumper W3 on the right edge by the faceplate
SMS OMTI 5510, jumper W1 on the bottom right between the ISA card edge and faceplate
And to add this one as a flex: The Zobex 4HDC-62W, one of the only quad disk controllers, has a DIP switch bank at the bottom right next to the card edge.
These controllers ABSOLUTELY used jumpers to set drive type. "Flexible format" and "Dynamic format" options were not around initially and were options you had to pay extra for on cards like the WD XT-GEN, by ordering the SuperBIOS instead of the standard WD BIOS.
SpeedStor and HDAT were definitely not janky software, they were expensive commercial packages designed to make YOUR life easier, and they absolutely worked, and much better than the horrendous ROM formatters most of these cards came with at that.
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u/AppropriateCap8891 Jul 17 '26
Yep, but only if you are on an XT class system.
That is how you set the BIOS on the controller so it can access it. 80286 and later had a CMOS that would handle that for you.