Floppy controller on 5170 AT

[csulaguy]

Hello y'all. Just joined this forum after numerous google searches. I've been collecting vintage hardware for a while, but recently acquired an AT (been wanting one for a while; had a 5162 286 XT that I trashed about 15 years ago, which was a big mistake on my part).

Anyways, it came with a 3.5" floppy installed. I can't tell if it's 720K or 1.44M, but either way, I have the first bios revision (1/10/84).
Can I use a floppy controller, either 8 or 16 bit, with its own BIOS and just tell the setup program that no floppy drives are installed?
I also purchased an XT-IDE controller on ebay, so I plan on booting up from Compact Flash anyways, although it would be nice to use the RLL controller to test out drives.

 

[modem7]

Hello y'all. Just joined this forum after numerous google searches.

Welcome to these forums.

.. but recently acquired an AT

Lots of IBM 5170 information at http://www.minuszerodegrees.net

Anyways, it came with a 3.5" floppy installed. I can't tell if it's 720K or 1.44M, but either way, I have the first bios revision (1/10/84).

Per the information at [here], which you may have already seen:
* You presently have the ability to read/write 720K sized diskettes. (DOS version 3.2 or later required.);
* Assuming that your 3.5" drive is a 1.44M one, upgrading the motherboard BIOS to the final revision will give you 1.44M capability. (DOS version 3.3 or later required.)

Can I use a floppy controller, either 8 or 16 bit, with its own BIOS and just tell the setup program that no floppy drives are installed?

It is possible to use alternate floppy controller functionality, but three things 'spring to mind':

* Be aware that some cards designed for the PC and XT will not work properly in an AT.

* Be aware of the issue ("Known problem - POST error of 601") described at the bottom of [here].

* If your 5170 has the IBM supplied card, shown at [here], the floppy part of it cannot be disabled. However, something that has worked for me is to jumper the card so that the floppy portion sits at the secondary address.

 

[sergey]

The AT floppy controller supports 1.44 MB floppy drives, so no need to replace the controller. And just so you know all PC/AT floppy controllers are 8-bit (the 16-bit portion is only used for HDD interface).

As modem7 suggested, you can replace the BIOS with later revision, that would support 1.44 MB drives. I think there are also non IBM (AMI or Phoenix?!) BIOSes available, that might work better that IBM one. Alternatively you can try the 2M utility, which basically replaces floppy BIOS. And if you feel adventurous you can try my own floppy BIOS extension (see files section at the bottom of the page). You can put it either in the same EPROM as XT-IDE BIOS, or in a network cards' ROM socket (again no need for the new controller - yours already supports 1.44 MB drives).