• Please review our updated Terms and Rules here

Baffling High Density Floppy/Controller Issue

nc_mike

Experienced Member
Joined
Sep 28, 2014
Messages
473
Hi,
I have 5160 XT. It has a 256-640K system board (late model 4/86 BIOS). I want to have a high density 1.44MB 3.5” floppy drive as A: that is bootable. Also, too often, I come across applications that insist on installing from A: and no other drive. I am using DOS 6.2 BTW.

I have a Mini Micro FDC PII-151B high density floppy controller with its own BIOS. I removed the original floppy controlled and put this one in, but not before setting the jumpers so that there would not be any memory conflict. I have two half-height drives, one (for the A: drive) of them is a Teac 1.44 3.5” 235-HF drive with no jumper on the drive, the other is a half-height 360KB 5.25” drive.
Both drives work, but the 1.44 drive will not read 1.44 disks, it will only read, write, and format 720K disks.

I set the jumpers for the drives as follows – carefully following the original OEM installation manual for the card that I have in addition to the following online doc: http://museum.ttrk.ee/th99/i/C-D/50286.htm

• The card BIOS is enabled for use in a PC/XT (JP5 closed).

• There are 4 pairs of pins on Jumper 3, the first two pairs are for Drive A, the second two pairs are for Drive B. I made sure the first two pairs were open for 1.44M operation. I closed both pairs 3 and 4 for Drive B: for 360KB operation.

• As far as I can tell, there are no memory address issues – I tried all three suggested addresses ad none of them resulted in memory address conflicts.

• On the system board there is only one set of rocker switches and I set them SW7 and SW8 on as documented, any other combination results in 601 boot errors.

• I do have an InBoard/386 PC adapter and don’t know if that is involved. I read that the Inboard uses the original XT BIOS to boot initially. I also have an AboveBoard PC and also an XT-IDE CF drive.

Any insight on why the Teac 235-HF 3.5” drive isn’t reading 1.44MB floppies and only 720KB floppies? I throught that having a high density FDD controller with its own BIOS should make the 1.44MB drive able to read/write to 1.44MB and not just to 720K disks - ut after going over and over it - and trying every different variation on Jumper 3 - I'm stumped.

Regards,
Mike
 
Have you tried the Teac drive in a machine that does 1.44MB natively?

Have you tried another HD floppy of either size with the Mini Micro controller?
 
Have you tried the Teac drive in a machine that does 1.44MB natively?

Have you tried another HD floppy of either size with the Mini Micro controller?

I haven't tried another 3.5" drive. I do have a spare external Backpack with a Mitsumi (sp?) 3.5" floppy drive inside of it that I could pop out pretty easily and try it in place of the Teac....it an idea...

Mike
 
There might be a bug when using that controller on certain machines/mobos similar to the one mentioned on modem7s page http://www.minuszerodegrees.net/transfer/35_inch/35_inch_drive.htm

That's an option. I'm not sure that bug prevented reading from the 1.44M drive though, sounds like it was only the ability not being able to boot, but I can't even read 1.44 disks, just 720. It is interesting it worked on an earlier XT bios and not the later one that I also have the same version. Humm....

Regards,
Mike
 
Maybe modem7 can give us some more detail.

It'd be interesting to see if DrDos 7, as opposed to MS/PC Dos, gets around these issues.
 
Last edited:
I'm not sure that bug prevented reading from the 1.44M drive though, sounds like it was only the ability not being able to boot,
Maybe modem7 can give us some more detail.
Boot problem only; reading was okay.

What surprised me was that the problem cause was in the final BIOS and not the first, opposite to what you would expect.
 
I've got a couple of the same controllers, and at least one is in use in an XT clone with no issues.

Do you see the DTK sign-on from the ROM?
 
• I do have an InBoard/386 PC adapter and don’t know if that is involved.
I have experienced InBoards (and other accelerator cards) cause strange issues, even at boot time when such cards are normally running the system at 'slow' speed.

I also have an AboveBoard PC and also an XT-IDE CF drive.
Not needed to boot the computer, and so you could quicky prove that they are not the problem cause.
 
A long shot but what happens if you select JP5 to open?

Yes, I did try disabling the card BIOS using JP5 thinking the 386 Inboard BIOS might take over, but no luck.

I also tried pulling pretty every non-essential board out of the system including the AboveBoard, same symptoms.

I do know the InBoard BIOS take over after initial boot, but I don't know its effect, if any on an external add-in FDD adapter.

Mike
 
A couple of thoughts: Since you can read and write to 720K disks, that suggests there isn't a hardware conflict. Those usually prevent the FDC from working at all. Can you use DEBUG to see the contents of the ROM? If you see the ROM you expect, then there shouldn't be any conflict. Does the floppy controller BIOS display any information at bootup? If it does and is not showing up when it should, then the BIOS might not be initializing.

Perhaps test writing to the drive with ImageDisk. That should bypass anything DOS or BIOS thinks.
 
A couple of thoughts: Since you can read and write to 720K disks, that suggests there isn't a hardware conflict. Those usually prevent the FDC from working at all. Can you use DEBUG to see the contents of the ROM? If you see the ROM you expect, then there shouldn't be any conflict. Does the floppy controller BIOS display any information at bootup? If it does and is not showing up when it should, then the BIOS might not be initializing.

Perhaps test writing to the drive with ImageDisk. That should bypass anything DOS or BIOS thinks.

No, I don't get any boot-time FDC BIOS message. I can try some of the other suggestions here tomorrow. Thanks!

Mike
 
Indeed you need to check if the rom on the card is working / the right one / or maybe is bad..

If it would work, it shows you a message that 1.44MB option is enabled.
 
Indeed you need to check if the rom on the card is working / the right one / or maybe is bad..

If it would work, it shows you a message that 1.44MB option is enabled.

I am not sure exactly how to check the cards BIOS with DEBUG. I did try a few other variations to rule out a few things. It definitely doesn't give me a message that message that the 1.44MB option is enabled on boot.

Because the XT in question has an 80386 Intel InBoard that takes over the BIOS after the base XT BIOS boots, I tried using the same card and drive in a 2nd stock 8088 PC/XT with a 64-256K system board. I and pulled out every adapter except the display adapter to get to a bare bones setup and ended up with the same result. I could read 720K disks and not 1.44 disks. So at least I ruled out any conflicts with other boards, and verified that the InBoard isn't in the equation.

I also tried using 2M-XBIOS on my main XT with the InBoard/386 and it didn't like it - it sensed it wasn't an XT (likely due to the InBoard/386 and suggested I try using the 2M-ABIOS which is for a PC/AT, but when I went to use the 2M-ABIOS is locked up my machine - so I guess even 2M-ABIOS doesn't like the Inboard/386.

I feel certain I've got the drive configuration jumper pairs set properly. The first two pairs are to be open for a 1.44 drive and is. So I am beginning to think the BIOS on the adapter is bad.

Regards,
Mike
 
I am not sure exactly how to check the cards BIOS with DEBUG.

Just start debug and type

D CA00:0000

or

D CC00:0000

or

D CE00:0000

depending on what address you set the card for. You should see something besides emptiness. (not rows of FF FF FF FF FF FF FF....) You may or may not see some text, such as a copyright notice.
 
Also played with the rom address on the floppy card? Maybe you have to see in which part of the upper memory does have empty spaces in the memory table. Maybe its just a ROM conflict.
 
Just start debug and type

D CA00:0000

or

D CC00:0000

or

D CE00:0000

depending on what address you set the card for. You should see something besides emptiness. (not rows of FF FF FF FF FF FF FF....) You may or may not see some text, such as a copyright notice.

OK, I ran debug against those addresses and got nothing but zeros for all three.

Regards,
Mike
 
I thought that might be the issue, which is why I tried the same card and disk drive on a different bare bones XT. The Mini-Micro FDC PII-151B manual has 4 sets of jumper pins, and they suggest 3 addresses which are CA00H-CBFFFH, CC000H-CDFFFH, and CE000H-CFFFFH. The card works in all three addresses in low density mode, just not in high density. I tried again a few min ago on the main XT, and when rebooting hit F8 to prevent config.sys from overtly loading things in to high memory as well, such as the frame for the Aboveboard, but then again, the AboveBoard nor any other cards except for the video adapter was installed (except that in both systems I do have an XT-IDE adapter as my hard drive - I could remove that one as well but haven't tried yet).

Mike
 
Maybe the ROM of the chip is empty, i think an eprom reader would give you more information if everthing is really zero or not.. Otherwise your rom is empty. So you need a new rom information.
 
Last edited:
Back
Top