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View Full Version : IBM PC/AT Floppy drives and Expanded/Extended memory



k2x4b524[
May 16th, 2012, 06:23 PM
Ok, here's whats up. As stated in another thread, i got my AT up and running again, but with 2 main issues. The AT Itself refuses to do 1.44mb floppies, via driveparm or other wise. I'd like to know if i can put my 16bit Everex MFM / Floppy controller with it's own bios in the AT, if i do, will it work? i know some models of the AT have issues with 3rd party hard drive controllers, so if that doesn't work, i know how to bypass the bios itself, just tell it no floppies and use my Acculogic floppy controller. OR i have a 16-bit IDE controller that sports 4 floppy support and is multi IO, if i do that, can i bypass the AT's bios for hard drives and floppies all together? If yes, i have a couple of bios boards i can throw in, but i'd like to use the MFM drive if i can, on the everex controller.

Issue 2

Expanded/Extended memory
I have in my AT an Everes Ram 3000, has 3 MB on board, it can add conventional ram, and supports expanded and extended on the same card. It does this admirably, but i can't get qram to work properly with it. I don't know what version of EMS it uses, and it's driver will only allow 1 64kb page frame for EMS so qram won't budge with it, just says to disable the page frame to get the umb, which is fine, as i can set the card up to do only 64kb of ram for expanded. My Question is this. Is there an updated driver that will allow qram to work with it? The version i have is 4.03 and is VERY command line limited, i have an intel above board PS/AT but no disk for it, it's got 2mb on it *i believe* but i'd really like to get the everex board working fluently in the AT with qram, expanded AND extended ram, *my 8mb above board is occupied*

Chuck(G)
May 16th, 2012, 06:37 PM
Any reason you simply don't want to upgrade the AT's BIOS? Later AT BIOSes do support 1.44M. As I mentioned before, there's nothing intrinsically wrong with the controller hardware--it's all software--in this case, the BIOS.

If you need proof of this, I can attach a small program that formats 1.44M floppies on your AT.

krebizfan
May 16th, 2012, 07:22 PM
Regarding the RAM board, the answer is that the single 64KB page frame is all you get. See http://support.microsoft.com/kb/31381

You will need a board designed later to get the full benefits of EMS 4.0 with multiple page frames that can be used with UMBs.

k2x4b524[
May 16th, 2012, 08:13 PM
That's kind of what i was afraid of, even with the drivparm it spits out general failure, and 720kb parameters not supported by drive. I've got my chip burner board, eraser and burner dug out, so i can just plug them in to the AT, install the software *if i can find it* and do that, unless there is a specific chip or code you need to do it, until then, can one just yank the stock controller? Mine is an earlier at i'm assuming as evidenced by the lack of bios support for the 1.44mb drives.

k2x4b524[
May 16th, 2012, 08:15 PM
I was afraid of that, i don't intend on using expanded on it anyway, i was just trying to get qram to work, which it will within that 64kb page frame. Unless anyone has information on the Intel Above Board PS/AT, or if my 8mb above board is in fact a 4.0 board.
Also means in need to try to find more EMS boards...

[QUOTE=krebizfan;225580]Regarding the RAM board, the answer is that the single 64KB page frame is all you get. See http://support.microsoft.com/kb/31381

You will need a board designed later to get the full benefits of EMS 4.0 with multiple page frames that can be used with UMBs.[/QUOT

Chuck(G)
May 16th, 2012, 08:21 PM
BIOS is a piece of soup (duck cake).

http://www.minuszerodegrees.net/rom/rom.htm

Just pick up the November 15, 1985 versions. Has the bonus that you get more hard drive types.

k2x4b524[
May 16th, 2012, 08:26 PM
Awesome, but there are 2 files, is that indicative of the 2 different chips?

And just my luck, i've only got 27128s.. but the file sizes are only 32kb in size, can i even get away with a 64kb eprom? I downloaded the AMI bios, the one with built in setup capabilities,

Chuck(G)
May 16th, 2012, 08:37 PM
Awesome, but there are 2 files, is that indicative of the 2 different chips?

U27 and U47. There are apparently two versions of the BIOS. Maybe Modem7 can explain that one.

k2x4b524[
May 16th, 2012, 08:45 PM
there are 2 versions, but i'm going to opt for the AMI version of the bios, ami and me get along for the older bios code for some reason. Just need to find some 27256 or 27c256. they are compatible right? Or can u use a smaller chip..

modem7
May 17th, 2012, 12:21 AM
, but i'm going to opt for the AMI version of the bios, ami and me get along for the older bios code for some reason. Just need to find some 27256 or 27c256. they are compatible right?
For this purpose, you can use either 27256 or 27C256. The chips will need to be rated at 150 nS or faster.


Or can u use a smaller chip..
No. The code will not fit into a smaller chip.

mikey99
May 17th, 2012, 07:52 AM
Have you tried using the GSETUP utility to set the drive type to 1.44 ?
I recall having a utility that I used on my AT to force the drive type to 1.44.
I think it was called C144.com or sthg similar.

k2x4b524[
May 17th, 2012, 10:53 AM
Yes, I have tried g-setup to no avail.

k2x4b524[
May 17th, 2012, 10:54 AM
Crud.....


For this purpose, you can use either 27256 or 27C256. The chips will need to be rated at 150 nS or faster.


No. The code will not fit into a smaller chip.