Old MFM controller on a PCI bus machine

From: Teo Zenios <teoz_at_neo.rr.com>
Date: Mon Jan 26 15:34:28 2004

----- Original Message -----
From: "Vintage Computer Festival" <vcf_at_siconic.com>
To: "Classic Computers Mailing List" <cctalk_at_classiccmp.org>
Sent: Monday, January 26, 2004 1:43 PM
Subject: Old MFM controller on a PCI bus machine

> I haven't played with MFM hard drives and controllers in a LONG time
> (about 10 years now) so I have some questions.
> I'll start off easy. Should there be any reason an old 16-bit ISA MFM
> controller won't work properly in a Pentium-class PC with ISA and PCI
> slots? I imagine I would just have to configure the BIOS to reserve the
> proper interrupt (I believe it's 14, correct?) for the MFM controller.
> I did all this but the MFM controller wreaked havoc on the system. It
> killed the on-board floppy disk and IDE controllers (not physically killed
> but basically disabled them and the system couldn't boot).
> I'm trying to determine if there is a natural conflict before I venture
> forth with this configuration. This may be a problem related to the PC
> I'm trying to plug the card into because there are other oddities with the
> IDE controller that is preventing the system from booting with 4 hard
> drives installed (2 per IDE interface). It halts after it auto-recognizes
> the drives on the primary controller. Weird.
> Anyway, any insight would be appreciated.
> I'm going to do more experimentation in the meantime. I'll get another PC
> with ISA and PCI slots to work with, and will also find an old 386 to test
> the MFM controller on to make sure it is working fine.
> --
> Sellam Ismail Vintage Computer
> --------------------------------------------------------------------------
Anything that gets plugged into the ISA bus (that isn't PnP) has a hard
wired IRQ, DMA, and address space (some or all can be changed with jumpers
depending on the vintage and device). If the MFM is using IRQ 14 or 15 then
the primary or secondary PCI IDE controller  will have a conflict and not
work and wont boot. The PC architecture is pretty easy going so you wont
damage anything doing this. Go inside your BIOS and disable the built in IDE
controllers (if you cant change the IRQ on your MFM card). Next you can try
going to bios screen where the floppy and HD data is shown (usually first
menu) and manually type in the cylinder/heads/sectors data for the drive
your using (will have to be set to "USER" unless your lucky enough that the
bios tables has a setting for your exact drive in which case just select the
drive that matches yours). Assuming everything is ok you can then boot the
system to floppy and use dos to either format the drive for use or if the
drive was already formatted (with the current controller) and bootable it
will come alive. The last MFM drive I used was probably a 40mb drive on a
286 packard bell I had before IDE took over so its been over a decade since
I used one.
Generally devices on the PCI era motherboard can either be used or disabled,
they rarely will allow you to change important settings for HD controllers
(you have a choice of 2 irqs for serial ports and some changes for printer
ports but the rest is set). The last promise caching HD controller made for
the IDE PC bus (5030 model) came with a cable and ISA card that specifically
grabbed IRQ 14 or 15 from the ISA bus if you couldn't redirect your BIOS to
use the card instead of the built in IDE (a pain to setup).
Received on Mon Jan 26 2004 - 15:34:28 GMT

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