Floppy Issue

Discussion about old PC hardware.

Floppy Issue

Postby westygw » 2018-1-31 @ 23:41

So, this is a pretty strange issue and after scouring the Internet I haven't quite identified what it is.
I thought maybe, through some expertise, someone here might know more about what's going on.

I've got a later 486 motherboard w/ only ISA and VLB slots. In it is a am486 DX4 100MHz.
No matter what drive I boot from (5.25", 3.5" or HDD), the drive will either not-work or will begin booting, but then turn off (HDD spin down or Floppy light goes off) and it'll just say "STARTING MS-DOS" forever and hang.
The Motherboard doesn't have a controller on-board so I'm using an IDE/FDD host card.
I've tried both host cards and they're confirmed working.. but I get the problem with either one of them.
I've gone so far as to disable all of the extra features on the motherboard (though there are few) and still, nothing.
At this time the only thing attached to the PC, now, is the 5.25" drive, that I'm trying to boot MS-DOS 6.2 from.
Half the time it won't even try to boot and the FDD light won't come on, but if I just keep rebooting it over and over, eventually it'll try for a second.

Any tips? I'm at a loss.
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Re: Floppy Issue

Postby kixs » 2018-2-01 @ 00:10

When did it work last? What happened in the mean time?

Check that the Standard BIOS options are correct. Floppy type and so on. If the battery is too low or missing the settings might not get stored when booting.

When you get "Starting MS-DOS..." press key combo to skip processing config.sys and autoexec.bat - key combo depends on DOS version (F5, F8, Shift+F8...).

Check jumpers on I/O controller and cables. Try different slot.

Try loading safe bios options, disable internal and external cache.
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Re: Floppy Issue

Postby clueless1 » 2018-2-01 @ 00:12

Have you tried moving the controller card to different ISA slots?
Have you confirmed the IDE/floppy cables are properly oriented?
Is there plenty of slack in the cables? (I once had an issue that was because my cable was slightly too short, causing the tautness to pull it out of the drive slightly)
Confirm the ISA controller is full seated into the slot. Best way is to test the system outside of the case.
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Re: Floppy Issue

Postby westygw » 2018-2-01 @ 00:13

I haven't tried disabling the external cache.
This Motherboard was brand new and this is the first time it's been used. Fresh CMOS battery.
The two controller cards I've tried (on multiple ISA slots) work fine in a different PC and the jumpers appear to be configured correctly by the manuals.
I tried F5 and F8 to no avail, but I haven't tried Shift+F8.
I've tried a ton of BIOS options with very little success, but the only drive selected, currently is A: and it's set to a 1.2MB drive.
I'm having a horrible time with this thing haha.

I'm at work, but when I can I'll try and get some pictures of the Mobo and controllers.
Last edited by westygw on 2018-2-01 @ 00:17, edited 1 time in total.
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Re: Floppy Issue

Postby westygw » 2018-2-01 @ 00:15

clueless1 wrote:Have you tried moving the controller card to different ISA slots?
Have you confirmed the IDE/floppy cables are properly oriented?
Is there plenty of slack in the cables? (I once had an issue that was because my cable was slightly too short, causing the tautness to pull it out of the drive slightly)
Confirm the ISA controller is full seated into the slot. Best way is to test the system outside of the case.


I have confirmed that the cables are all the correct orientation and that the card is fully seated. I've also tried multiple ISA slots.
The cable is very slacked. No tension at all.

On every 20th to 30th boot it does work.. but only for a few seconds before hanging.
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Re: Floppy Issue

Postby kixs » 2018-2-01 @ 00:20

Could be a memory related problem.

- disable all caches
- try different SIMMs
Last edited by kixs on 2018-2-01 @ 00:21, edited 1 time in total.
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Re: Floppy Issue

Postby clueless1 » 2018-2-01 @ 00:21

Any BIOS settings for ISA bus clock rate? It should be no higher than 8Mhz. Also if there are memory timings, set them to defaults or detune them for testing purposes.

edit: might want to test the system outside of the case anyhow, just to eliminate any possible shorts with the case.
Last edited by clueless1 on 2018-2-01 @ 00:25, edited 1 time in total.
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Re: Floppy Issue

Postby westygw » 2018-2-01 @ 00:25

Could a memory problem really be causing this sort of deal? I'm not sure if I have any more 72-pin SIMMs around, but I'll surely find some to test with, somewhere.
I'll double check the ISA bus clock and memory timings as well as try some new things.
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Re: Floppy Issue

Postby squiggly » 2018-2-01 @ 00:58

Viagra.
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Re: Floppy Issue

Postby Baoran » 2018-2-01 @ 01:20

clueless1 wrote:Any BIOS settings for ISA bus clock rate? It should be no higher than 8Mhz. Also if there are memory timings, set them to defaults or detune them for testing purposes.

edit: might want to test the system outside of the case anyhow, just to eliminate any possible shorts with the case.


Too low isa bus clock can make that happen too. I once set it to 33Mhz divided by 10 and all the floppies started having data errors when I tried to read them.
Also I have had alot of bad luck with I/O cards too, I had to get 3 of them once before I found one that worked.

Also once switching a power supply suddenly made my floppy drive boot again, which was strange because when I tried the same power supply in a pentium class pc that had ide controller on the motherboard, the floppy drives booted fine there.
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Re: Floppy Issue

Postby westygw » 2018-2-06 @ 22:57

Sorry I haven't been responsive or posted any pictures.
I'm diagnosing everything remotely, so it's causing slowness.
What I've discovered is that the issue is corrected when disabling L1 cache.
L2 cache seems fine and if L1 is enabled and L2 is disabled, the PC constantly reboots.
So, once L1 cache is disabled, MS-DOS boots fine.

Some quick Internet research yielded a ton of useless answers like, "Did you try a different disk?" and "Try a different graphics card."
I've tried both of those :P
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Re: Floppy Issue

Postby Geforcefly » 2018-2-07 @ 02:17

I had a related issue with a Biostar MB1433 VLB motherboard + Cyrix DX4-100 in which the floppy drives would be flaky with L1 cache on. Annoying because of the MASSIVE performance hit for everything else it caused.
DOS/Win3.1: Packard Bell 386SX-II | 386SX-20 + 387SX | 8MB RAM | 13.6GB HDD @ 502MB | TVGA8900C 1MB | SB16
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Re: Floppy Issue

Postby westygw » 2018-2-07 @ 02:22

Geforcefly wrote:I had a related issue with a Biostar MB1433 VLB motherboard + Cyrix DX4-100 in which the floppy drives would be flaky with L1 cache on. Annoying because of the MASSIVE performance hit for everything else it caused.


Were you able to find a solution besides simply running no L1 cache?
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Re: Floppy Issue

Postby Geforcefly » 2018-2-07 @ 02:55

No. This was also back in 1996.
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Re: Floppy Issue

Postby westygw » 2018-2-07 @ 08:18

http://www.elhvb.com/webhq/models/486vlb3/4dms.txt.html

This is the manual (or something) for my Motherboard.
It says that it supports an "Enhanced AMD DX4", but I can't find any of the jumper settings for it.
The mobo isn't well documented on the actual hardware, so I'm at a loss.
My suspicion is that some freaky jumper setting is off.
EDIT: I should add that my CPU is just a regular Am486 DX4 100MHz. It's not in the jumper settings, either, though.
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Re: Floppy Issue

Postby Jo22 » 2018-2-07 @ 19:13

No matter what drive I boot from (5.25", 3.5" or HDD), the drive will either not-work or will begin booting,
but then turn off (HDD spin down or Floppy light goes off) and it'll just say "STARTING MS-DOS" forever and hang.
The Motherboard doesn't have a controller on-board so I'm using an IDE/FDD host card.
I've tried both host cards and they're confirmed working.. but I get the problem with either one of them

Uhm, do you say your are using two separate cards (IDE and FDC) ?
I recall that this can be troublesome sometimes.

I vaguely remember there was a signal (RDY/Ready),
which combo cards would usually take care for.

Sorry, my mind is quite a bit sketchy about the matter..
I searched the forums, but can not seem find that thread anymore. :sweatdrop:
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Re: Floppy Issue

Postby westygw » 2018-2-08 @ 00:18

Jo22 wrote:Uhm, do you say your are using two separate cards (IDE and FDC) ?


I'm using one host card that has IDE and FDC onboard.
I think I mentioned that I have two cards, but they're just two separate Host cards that I was trying. They both seem to work okay.
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Re: Floppy Issue

Postby westygw » 2018-2-15 @ 07:33

After much trial.. and much error.. it all works.
I found an archived copy of the mobo manufacturer's website.. and got a copy of their config utils.. and ran them in Windows 3.11 in DOSbox..
..to get the correct jumper settings.
Now everything is working and things are great.
Thanks for all the help and advice, everyone. The issue was with the L1 Cache settings for whatever CPU it was wrongly configured to.
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