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NOTE:

This web site is not some kind of 'official' documentation hub for the XT-IDE card. It is simply the result of someone who decided to add to the documentation that exists elewhere.

VCF XT-IDE  -  Coexistence with an MFM hard drive controller card



MFM hard drive controller of XT-class

It is possible for a VCF XT-IDE card to coexist with an XT-class MFM hard drive controller card.

For example, I have done it by adding my VCF XT-IDE Rev 1 card to a clone XT computer of mine.  A photo of that configuration is at here.  A diagram of that configuration is at here.

As shown here, when I power up the computer, the early revision of XTIDE Universal BIOS (XUB) in my card gives me the choice of hard drive booting from either the ST-225 drive (the "Foreign Hard Disk") or the CF card (the "SanDisk SDCFB-32").  I then use the up/down arrow keys on the keypad to select what I want to boot from, then press the ENTER key.

As for other examples, I have also had my XT-IDE Rev 1 card coexisting with an IBM Fixed Disk Adapter, in both an IBM 5150 (10/27/82 BIOS fitted) and IBM 5160.

In the above examples, I used a Rev 1 card.  I expect that later revisions of the XT-IDE card will coexist too.

IMPORTANT:	Make sure that the MFM drive is successfully booting in the computer before (repeat: before) you add the XT-IDE card.  That is because the XT-IDE card will default to booting from the MFM drive.
IMPORTANT:	The ROM in the XT-IDE card needs to be sitting at a higher address than the ROM in the XT-class MFM hard drive controller card.  That is normally the case  (XT-class MFM card = C8000, XT-IDE card = D0000).

MFM hard drive controller of AT-class

It is possible for a VCF XT-IDE card to coexist with an AT-class MFM hard drive controller card.

For example, I have done it by adding my VCF XT-IDE Rev 4 card to an IBM 5170 (IBM AT), an IBM 5170 that had its stock MFM controller and MFM hard drive fitted.
Because of a known problem, to get the IBM 5170 and XT-IDE combination working, I changed the 5170 motherboard's IBM BIOS to the Award one at here.

A diagram showing the situation is at here.

The version of the XTIDE Universal BIOS (XUB) that I had fitted to the XT-IDE card was V2.0.0 beta 3, and it lacked the optional boot menu.  So, by default, the MFM drive was the first hard drive and the XT-IDE's drive was the second hard drive.  The 5170 booted from the MFM drive (the first hard drive), with the MFM drive presented as logical drive C:, and the XT-IDE's drive presented as logical drive D:

If instead, I wanted to boot from the XT-IDE's drive, I would press the 'D' key when I saw the Hotkeybar shown by XUB V2.0.0 beta 3.  That made the XT-IDE's drive become the first hard drive, and the MFM drive become the second hard drive.  The 5170 booted from the XT-IDE's drive (the first hard drive), with the XT-IDE's drive presented as logical drive C:, and the MFM drive presented as logical drive D:

NOTE:

When I added (repeat: added) the XT-IDE to my IBM 5170, I did not adjust the C: and D: hard drive types in the 5170's SETUP (a.k.a. 'CMOS SETUP'). I did not need to. The XTIDE Universal BIOS does not use the drive types within the 5170's SETUP. In summary: * The AT-class MFM controller/drive is software controlled by the BIOS on the 5170 motherboard.  That BIOS uses the C: drive type in the 5170's SETUP to determine the geometry of the MFM drive. * The XT-IDE controller/drive is software controlled by the XTIDE Universal BIOS on the XT-IDE card.  That BIOS interrogates the IDE drive to determine the geometry of the IDE drive.