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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.  A diagram showing the situation is at here.  The cards can co-exist because they are very different from each other.


Background information

• The AT-class MFM controller/drive is software controlled by the BIOS on the AT-class motherboard.  That BIOS uses the C: drive type in the SETUP (CMOS SETUP) to determine the geometry of the MFM drive.

• The XT-IDE controller/drive is software controlled by the XTIDE Universal BIOS (XUB) on the XT-IDE card.  That BIOS interrogates the IDE drive (or CF) to determine the geometry of the IDE drive (or CF).  It does not use the C:/D: drive types stored in the SETUP (CMOS SETUP).


IBM 5170 (IBM AT) example #1 of 2 - MFM hard drive is faulty

In this example, the MFM hard drive attached to the 'IBM Fixed Disk and Diskette Drive Adapter' in my IBM 5170 has gone faulty, and I cannot find a suitable replacement MFM drive, and I want to use an XT-IDE card as a substitute for the drive.

I am leaving the 'IBM Fixed Disk and Diskette Drive Adapter' in place, because I need it to control the floppy drive.

STEP 1:  I remove the faulty MFM hard drive from the computer.

STEP 2:  Because I have a type 1 motherboard, in order to use an XT-IDE card on the type 1 motherboard, I have to upgrade the IBM BIOS on the motherboard to the 06/10/85 dated IBM BIOS.  You can see that requirement in note 1 at here.  I do that upgrade.

STEP 3:  The motherboard BIOS still believes that an MFM hard drive is attached to the 'IBM Fixed Disk and Diskette Drive Adapter', and because it cannot find the drive, is still generating a 17xx error at start-up of my IBM 5170.  To get rid of that 17xx error, I run SETUP (see here) and set the C: drive type to 0 (zero).

STEP 4:  With power off, I plug in the XT-IDE card.

STEP 5:  I power on my IBM 5170, see the XTIDE Universal BIOS (XUB) appear on-screen, then watch as the XUB boots from the IDE drive (or CF) attached to my XT-IDE card.


IBM 5170 (IBM AT) example #2 of 2 - I want the IDE drive on the XT-IDE card to complement the existing MFM hard drive

In this example, I want the IDE drive (or CF) attached to my XT-IDE card to become the second hard drive in my IBM 5170.

Background: The version of the XTIDE Universal BIOS (XUB) that I have fitted to the XT-IDE card is V2.0.0 beta 3+

STEP 1:  Because I have a type 1 motherboard, in order to use an XT-IDE card on the type 1 motherboard, I have to upgrade the IBM BIOS on the motherboard to the 06/10/85 dated IBM BIOS.  You can see that requirement in note 1 at here.  I do that upgrade.

STEP 2:  With power off, I plug in the XT-IDE card.

STEP 3:  I power on my IBM 5170, see the XTIDE Universal BIOS (XUB) appear on-screen, then watch as the XUB boots from the MFM drive.

So, by default, the MFM drive is the first hard drive and the XT-IDE's drive is the second hard drive.  The IBM 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 want to boot from the XT-IDE's drive, I would press the 'D' key when I see the Hotkeybar shown by XUB V2.0.0 beta 3+.  That will make the XT-IDE's drive be the first hard drive, and the MFM drive be the second hard drive.  As a result, the IBM 5170 will boot from the XT-IDE's drive (now, the first hard drive), with the XT-IDE's drive presented as logical drive C:, and the MFM drive presented as logical drive D:

Optionally, if I want the IBM 5170 to boot from the XT-IDE's drive by default (i.e. I don't need to press the 'D' key), I can do that by reconfiguring the XUB in the XT-IDE card, specifically, changing the 'Default boot drive' setting to 81 (eighty one).