From: faruque@sun.soe.clarkson.edu (Abdullah Faruque,334CH,3752,2654247)
Subject: Re: IDE HD and MFM (XT) HD in the same AT ?
Organization: Clarkson University
Date: Fri, 21 Aug 1992 23:55:26 GMT

From article <jmh.714382322@tko.vtt.fi>, by jmh@tko.vtt.fi (Michael Hasemann):
> Hi Netters,
> I would like to use an IDE HD and a XT HD in the same AT.
> 
> Is that possible ?
> Any hints appreciated.
> 
> Regards Michael

Yes, it is possible to run both IDE and MFM/RLL drives together.
Currently I am using a 80 meg IDE (Maxtor 7080A) and a 65 meg RLL
(Seagate ST277R-1) drive together in a 386 machine. I have seen this
question several times, so I compiled the following summary about this
matter. There are three ways it can be done:

1. You need the right MFM/RLL controller card which can be set at the
secondary hard drive port address with the onboard BIOS enable. Also
the onboard BIOS must support hard drive at the secondary port
address. The only 16-bit MFM/RLL card (as far as I found) that
fulfills those requirements is the Seagate ST21/22M (MFM model) or
ST21/22R (RLL model). Although most other RLL cards (I have tried
Wester Digital, Adaptec and DTC) in the market do have an onboard
BIOS and jumpers to set it at a secondary port address, but they will
not work as a secondary controller.  Probably the onboard BIOS of
those cards can not support hard drives at the secondary port address.
This problem may be solved by loading a device driver through the
operating system, but this kind of device driver is not available (as
far as I know) from the manufacturer or from any ftp sites. So, you
may have to write one and which may not worth your time and energy.

So, get a ST21/22M or ST21/22R controller card and you are all set.
Currently I am using a ST21/22R in my system. It runs without any
problem with DOS 5.0, WIN 3.1. The following are some points that need
to be considered while using IDE and MFM/RLL together.

(i) If you already own a MFM/RLL drive (which is sitting around and
collecting dust) then you just need a ST21/22 controller (they are
around $45 new) and get some extra space. If you have to buy a MFM/RLL
drive also, then probably it is not worth, instead buy a second IDE
drive (which will be more cost effective).

(ii) The onboard BIOS of the MFM/RLL card takes some memory space from
the UMB (memory between 640K and 1meg). So, you have to configure your
memory manager (EMM386, QEMM etc.) to exclude that area if your memory
manager unable to detect ROM BIOS of the controller card to avoid
software conflicts.

(iii) You have to disable the floppy part of the ST22M or ST22R
when using it as a secondary controller. There are jumpers to disable
the floppy part. ST21M or ST21R does not have any floppy support.
Your floppy drive should be run by the IDE host adaptor or a floppy
only controller card at the primary floppy drive port address.

(iv) You can only use one MFM/RLL drive (as D: drive) in conjunction
with only one existing IDE drive (the C: drive). Although the MFM/RLL
controller supports two hard drive but that will work only in the
stand alone mode. The onboard BIOS of ST21/22 is not yet capable of 
recognizing any drive beyond C: and D: drive.

2. The second method is to use an IDE host adaptor card that can
co-exist with other MFM/RLL controllers. I have seen these kind of
product advertised in Computer shopper, they are expensive too. I
never used one, so I can not tell much about it. If somebody has any
experience, then I would like to hear about it.

3. The third method is to use a 8-bit XT type MFM/RLL controller card.
Some of these type of cards (not all of them) can be configured as
secondary controller and can co-exist with other types of primary
controller cards.  I will not recommend this method, because you will
get poor performance with an 8-bit card in an AT type machine.

I would like to here if there is any other possible ways of doing this.

-Faruque
Email: faruque@sun.soe.clarkson.edu










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