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Compaq Deskpro detects 3.5 FDD as 5.25 FDD - need ideas

normanator

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Hello all. Have been working on un-mothballing a Compaq Deskpro 386/25 I've stored away for 18 years. Entire system still works splendidly except one issue: getting it to properly recognize a 3.5 1.44MB floppy drive. The system sees the drive, but no matter what I've tried, the Compaq Setup program and the CMOS always detect the 3.5" as a 5.25 1.2MB drive. Putting a disk into the 3.5" drive and doing "dir" causes the usual "Abort, Retry Fail?", except that selecting "Fail" will *sometimes* allow it to read the disk contents. Usually it just fails entirely or tries to read the directory table and issues a nasty "INT24 failure" error. I'm guessing the partial success is just a coincidence with how 5.25 and 3.5 directory tables are stored. But it definitely won't access any files.

I really don't recall having this issue when I boxed it up, but admittedly it's been many years.

Here's the configuration:
  • Using a Compaq ESDI controller card (P/N 000996) to drive 2 FDDs and a 315MB HDD.
  • FDD 1 = 5.25" 1.2MB (works fine)
  • FDD 2 = 3.5" Teac FD-235HF 1.44MB with adapter, common for it's day (see picture)
IMG_2036.jpgIMG_2034.jpgIMG_2035.jpg

What I've tried:
  • There don't appear to be any jumpers or switches on the ESDI card to set drive types, only IRQ settings and such. I've included a pic of the ESDI jumper and SW500 settings (the red switch block at the top of the card). All are set to default positions, and have not moved since last using this machine years ago.
  • I've added DRIVPARM /D:1 /C /F:7 /I in the config.sys to try and force DOS to see the correct type. No joy.
  • I've tried a different known good working 3.5" FDD, but same problem.
  • I've tried enabling the OP setting on the FDD adapter, which brings in pin 34. No idea what that setting does, but didn't make any difference. The default position is OP=OFF.
What I haven't tried yet is swapping the cable position of the 5.25 and 3.5 and/or removing the 5.25 and/or leaving the 3.5 as the only drive in the system, because I only have a 5.25 Compaq setup disk and changing the configuration makes the BIOS force me to run Setup again. Working on finding and creating a 3.5 setup disk, but I'm confident that's not going to fix anything. And, the drive should be recognized correctly no matter it's position.

Never had this issue before with any PC, and not sure where else to go. Any insights or ideas are appreciated.
 
what version of DOS are you using? My Compaq Quick Reference Guide says that to use a 1.44MB floppy drive, you need at least MS-DOS 3.31 Rev A to use it as the B: drive, or MS-DOS 3.31 Rev B to use it as the A: drive. I understand "MS-DOS" in this context to mean specifically a Compaq release of MS-DOS, but it would be reasonable to expect a Microsoft-branded release of MS-DOS 5 or 6 to work as well.
 
what version of DOS are you using? My Compaq Quick Reference Guide says that to use a 1.44MB floppy drive, you need at least MS-DOS 3.31 Rev A to use it as the B: drive, or MS-DOS 3.31 Rev B to use it as the A: drive. I understand "MS-DOS" in this context to mean specifically a Compaq release of MS-DOS, but it would be reasonable to expect a Microsoft-branded release of MS-DOS 5 or 6 to work as well.

Excellent thought, thanks! I didn't actually load the OS, and it reports as just "MS-DOS 5.0" when using "ver" command. Booting from diag disk reports "Compaq Personal Computer DOS ver 3.2". Hadn't thought about not having a bonafide Compaq DOS on it. But when I boot the Compaq diag disk (v5 diag), it definitely boots a Compaq image and it still won't recognize it correctly.

Other tidibts:
- Compaq diag reports system ROM revision K
- Norton Utilities sees it as a 1.44MB drive on the initial System Info page, but when I go to the drive parameters page, Norton reports it as 1.2MB 5.25. Gah!

Trying to find a 3.5" version of Diag v8. If anyone has one or knows a location offhand, thanks in advance.
 
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If you google SP0308.exe you'll find it. It needs to be run from a DOS-like system though, it doesn't seem to like NT based stuff, or maybe it just doesn't like 64bit. I'm not sure.

I ran it a while back, and then used winimage to make a more portable image. It doesn't seem to be bootable though, so I don't know if I screwed something up or if it's expected to boot it from a DOS bootdisk first.

https://www.dropbox.com/s/c21gzruon2v9d2x/compaq_setup_720k.IMA?dl=0 (this link will probably stop working after a few days, because I'm just using the free version).
 
Hello all. Have been working on un-mothballing a Compaq Deskpro 386/25 I've stored away for 18 years. Entire system still works splendidly except one issue: getting it to properly recognize a 3.5 1.44MB floppy drive. The system sees the drive, but no matter what I've tried, the Compaq Setup program and the CMOS always detect the 3.5" as a 5.25 1.2MB drive. Putting a disk into the 3.5" drive and doing "dir" causes the usual "Abort, Retry Fail?", except that selecting "Fail" will *sometimes* allow it to read the disk contents. Usually it just fails entirely or tries to read the directory table and issues a nasty "INT24 failure" error. I'm guessing the partial success is just a coincidence with how 5.25 and 3.5 directory tables are stored. But it definitely won't access any files.

Typically most computers (and the BIOS setup utility) are not designed to attempt to "detect" the type of floppy drive that has been installed. You have to use "Setup" utility provided for this purpose by Compaq to manually configure the second physical floppy drive to the type of drive actually installed. The Setup utility should allow you to manually change the type of floppy drive actually installed from its default selection, which (for this old DeskPro) is likely for both drives to be configured as 5.25" drives. If you have successfully changed this setting, and as you stated this DeskPro is booting up MSDOS v5, this 3.5" drive should work properly. If it doesn't, it may be (but unlikely) the Compaq BIOS is reporting the type of attached drive in some manner that only works properly with "Compaq DOS".
Incidentally you also need to make sure the BIOS backup battery works - otherwise the moment you turn the computer off the manual configuration you performed will be lost, and the floppy drive configuration will return to its default setting.
 
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The Setup utility should allow you to manually change the type of floppy drive actually installed...
Thanks. I had been using the Compaq Setup v5.00 utility, but it didn't allow for changing the auto-detected FDD types. Found and burned a copy of the Compaq Setup v8.00B utility, which lets me change the type and that solved the problem.

Incidentally you also need to make sure the BIOS backup battery works - otherwise the moment you turn the computer off the manual configuration you performed will be lost, and the floppy drive configuration will return to its default setting.
After a handful of leaked CMOS battery incidents over the years, I've adopted a policy of plugging in a battery only for the duration I'm actively using the computer. I have an extensive collection of PC/XT/AT computers, and most don't get rotated out of storage very often. Therefore, I pull the CMOS battery when the unit goes back into storage. Worst case, when I pull it out again I have to set the date and time or run a setup utility. Not a big trade off vs risk of corrosion damage IMO.

On a related topic, this whole process did allow me to discover 2 inoperative 3.5" FDDs. Both are Teac FD-235HF models with electrolytic capacitors on the circuit board that have gone bad. Replacement caps on order. Once that's complete, I'll have a fully original, functional unit!

Thanks to all for the assist! :cool:
 
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