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laos101
May 16th, 2017, 11:08 AM
Hi,

This might be a stupid question as I'm a novice in the VC world. Is it possible to connect a 3.5-inch floppy drive to a 34 pin floppy controller on a compaq portable (8088)? Would the BIOS recognize it OOB or would I need some sort of modification?

I'm trying to get DOS up and running on the one I own which only has two 5.25 floppy drives and I have no easy way to write the 5.25 floppies from any of my modern or early 2000s equipment.

I do have a XT-CF-IDE in the mail, but I also want to have DOS or a compaq setup disk as a backup if at all possible...

Feel free to point me in the right direction if there's an easier way of doing all this!

rvdbijl
May 17th, 2017, 06:54 PM
Hi,

This might be a stupid question as I'm a novice in the VC world. Is it possible to connect a 3.5-inch floppy drive to a 34 pin floppy controller on a compaq portable (8088)? Would the BIOS recognize it OOB or would I need some sort of modification?

I'm trying to get DOS up and running on the one I own which only has two 5.25 floppy drives and I have no easy way to write the 5.25 floppies from any of my modern or early 2000s equipment.

I do have a XT-CF-IDE in the mail, but I also want to have DOS or a compaq setup disk as a backup if at all possible...

Feel free to point me in the right direction if there's an easier way of doing all this!


I may not have a whole lot to offer on your original question, but I do remember a long time ago trying to get a 3.5" drive (non-HD) to run on an XT and I think I did manage to get that running.. Fdread or a similar tool comes to mind. Somehow you have to trick the adapter into thinking the drive has 80 tracks, not 40. 720Kb is still 2 sided and 9 sectors/track, so technically the controller should be able to handle it.

That said, I am very curious if your XT-IDE will work in your Compaq Portable. I have a Compaq Portable as well (BIOS date in '82), and it seems to be of the vintage that doesn't scan for option ROM's in the C000-EFFF range. So my XT-IDE won't boot in that system unfortunately. If yours does... I'd be very interested in a memory dump of your F000-FFFF segment so I can try to write a new BIOS EPROM for my Compaq. I read somewhere that Compaq released an updated BIOS for the Portable I which does scan for option ROM's. No idea if that went hand-in-hand with a mainboard hardware update, but I figured it's worth a shot!

modem7
May 18th, 2017, 02:22 AM
Is it possible to connect a 3.5-inch floppy drive to a 34 pin floppy controller on a compaq portable (8088)? Would the BIOS recognize it OOB or would I need some sort of modification?
If that is done on an IBM PC, a similar spec'ed computer, it is discovered that 1.44M diskettes do not work, but [720K] (http://minuszerodegrees.net/images3/3.5_dd_hd_difference.jpg) ones do. Primarily, this is because the floppy controller can handle double-density but not high-density. Your early Compaq Portable may be the same.

Take a look at the web page at [here (http://minuszerodegrees.net/5150/floppy_diskette/5150_floppy_drive_support.htm)] for what is required to get 1.44M diskette operation in an IBM PC. I do not own an early Compaq Portable, and so I cannot say that it also applies to the early Compaq Portable, but it gives you an idea of what may be required.

laos101
May 18th, 2017, 07:26 PM
I may not have a whole lot to offer on your original question, but I do remember a long time ago trying to get a 3.5" drive (non-HD) to run on an XT and I think I did manage to get that running.. Fdread or a similar tool comes to mind. Somehow you have to trick the adapter into thinking the drive has 80 tracks, not 40. 720Kb is still 2 sided and 9 sectors/track, so technically the controller should be able to handle it.

That said, I am very curious if your XT-IDE will work in your Compaq Portable. I have a Compaq Portable as well (BIOS date in '82), and it seems to be of the vintage that doesn't scan for option ROM's in the C000-EFFF range. So my XT-IDE won't boot in that system unfortunately. If yours does... I'd be very interested in a memory dump of your F000-FFFF segment so I can try to write a new BIOS EPROM for my Compaq. I read somewhere that Compaq released an updated BIOS for the Portable I which does scan for option ROM's. No idea if that went hand-in-hand with a mainboard hardware update, but I figured it's worth a shot!

Do you get to the BIOS? I get to the BIOS of my XT-IDE-CF OPTIMA but the 2GB CF card(detected by the system) doesn't boot, but it could be whoever I bought it from didn't put on something that works for a machine with only an 8086. I just get stuck on "Booting C>A" which I presume is the boot order configuration, and then it just hangs there eternally.

The keyboard is from October 1984, so my guess is that the unit was built somewhere around mid 1984. Unfortunately I am quite the novice so I dunno where to start with giving you a BIOS dump, hence why I'm struggling to even get DOS to boot :)


If that is done on an IBM PC, a similar spec'ed computer, it is discovered that 1.44M diskettes do not work, but [720K] (http://minuszerodegrees.net/images3/3.5_dd_hd_difference.jpg) ones do. Primarily, this is because the floppy controller can handle double-density but not high-density. Your early Compaq Portable may be the same.

Take a look at the web page at [here (http://minuszerodegrees.net/5150/floppy_diskette/5150_floppy_drive_support.htm)] for what is required to get 1.44M diskette operation in an IBM PC. I do not own an early Compaq Portable, and so I cannot say that it also applies to the early Compaq Portable, but it gives you an idea of what may be required.

Thanks for sharing. I know the drive is detected as I'm not getting any error codes at boot, and I get a 601 at some points if I'm not hooking everything up properly. I also have tried 720k and 360k floppies through the emulator, but no dice. It can be a host of things ranging from my jumper configuration, to my cable, to the actual images I'm trying to use, so I guess I'll just keep debugging and report back if I am successful. I was wondering if by chance anyone here might know a good jumper configuration to try based on this doc from the chinese manufacturer: http://iw.suntekstore.com/images_cache/270/10019783/136383371310019783.pdf

PhilipA
May 19th, 2017, 04:25 PM
I crimped a connector onto the original ribbon, added the correct power plug piggybacked into the original Molex. I have a 1.44Mb Sony floppy drive hooked up. It'll read and write on my controller at 720k. I've had success formatting HD discs at DD sector size and it'll read them (drive supports the higher flux with the hole uncovered)
I added an NEC V20 to mine, burned the image for it and got my XTIDE working nice and fast. 8Gb compact flash card partitioned into 4 chunks using a newer computer. Was a mild hassle to set up but it works very very well.

Phil

modem7
May 20th, 2017, 02:54 PM
Unfortunately I am quite the novice so I dunno where to start with giving you a BIOS dump,
rvdbijl was able to get a suitable BIOS via another thread.

Casey
May 20th, 2017, 04:25 PM
Back in the day I had a Portable which included a 3.5" floppy connected to the standard controller. Acted just like an XT in that it only recognized 720K floppies.