Formatting and verifying MFM hard disks

From: Fred Cisin <cisin_at_xenosoft.com>
Date: Thu Nov 27 15:33:37 2003

On Thu, 27 Nov 2003, Ian Primus wrote:
> As I have been sorting and cleaning over Thanksgiving, I decided that I
> would build up an extra PC clone for the sole purpose of formatting and
> verifying various types of media, such as SCSI, IDE, and MFM hard
> drives and 3 1/2 and 5 1/4 floppies. I originally planned on just
> tossing an MFM card and SCSI card into an older AMD K6-2 233, and
> installing two floppy drives. But, as I got started, I remembered how
> the old MFM drive controllers worked, and how they kinda take over the
> boot process.

ON XT.
On AT (You said AMD K6-2 233!), it is entirely an issue of what
your BIOS does.
(XT uses a BIOS extension ROM on the MFM controller card)

> Also, since MFM drives need to be low level formatted for
> a specific controller before they can be high level formatted,

ON XT, there were a lot of mutually incompatible hard disk low level
formats.
ON AT, the format was standardized, and is the same for virtually all
controllers.

> I can't
> really just format them from Linux.

why not?

> I found a Seagate card that has a
> nice boot screen with a drive formatting utility, but it only handles
> eight different Seagate drives. I've got a couple of other old
> controllers, none of which have such a nice utility, and all of which
> prevent me from booting from CDROM (they intervene before the BIOS
> boots from a disk, and when the MFM card can't boot a hard drive, it
> tries floppy drives, but it doesn't see the CDROM, and won't return
> control of the boot process back to the PC's built in controllers)

If you set the CMOS in an AT to "NO DRIVE", then it will not try to invoke
the MFM hard drive.
IFF your BIOS supports booting from CDROM, then you can. And MOST AT
BIOSes that support booting from CDROM also support letting you choose
boot device.
XT's do NOT support CDROM boot, unless you add an additional ROM (such as
is present on some SCSI controllers for the purpose of booting from a SCSI
hard drive)
For DOS, you need 3.10 or newer if you want CDROM access (the CDROM is
seen as a very Local Area Network, and uses the undocumented network
redirector) (There was an aftermarket driver set for using CDROM with
earlier versions of the OS, but it might not be easy to find)

> Also, in this process, I realized that I can't find my DOS disks! It's
> been a long time since I booted DOS, and an even longer time since I've
> messed with DOS on XT's, so I don't know where the disks are. What I

XT or AT? You mentioned "AMD K6-2 233", which would be a very unusual XT!

> think I need is a disk with DOS 3.x and debug. I remember having to use

3.10 or above if you want CDROM access
3.31 or above if you want access to FAT volumes larger than 32M


> debug to invoke the built in formatting program on most hard drive
> controllers.

You could write a trivial program (5 bytes) to do a far jump.

> Anyway, what I really want to do, is have a computer that would have an
> MFM card in it, and be able to work with any MFM drive. I'd also like
> to still be able to boot off an IDE hard drive or a CDROM, since I want
> to install Linux on an IDE drive on the motherboard's controller, and
> use that for high level formatting. I can probably work around that by
> having a Lilo bootdisk, and booting that first, then the system could
> continue booting from an IDE drive. But, if I did this, what is the
> best way to do low level formatting on MFM drives?

For DOS, "Speedstor"

> Is there a way to
> invoke the card's internal formatter from Linux? It's been a while

You could write a trivial program (5 bytes) to do a far jump.

> since I worked with this stuff, can anyone refresh my memory?
we all have our own "old-timer's disease" issues.
Received on Thu Nov 27 2003 - 15:33:37 GMT

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