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Baffling High Density Floppy/Controller Issue
- Thread starter nc_mike
- Start date
Chuck(G)
25k Member
Okay, perhaps you didn't notice that I had not one, but two of these cards--and they work.
Take a look at the way this card is set up. It matches one of mine; that is, the BIOS is set at CA00:0000 (use DEBUG as described above).
If you don't see that, then most probably (a) you have a hosed EPROM or (b) the EPROM is in its socket incorrectly. Look at the image above, make sure your EPROM is oriented the same way and that all pins are in the socket securely--i.e. none are bent.
If no luck there, you probably need a new EPROM with the image burned into it correctly.
Take a look at the way this card is set up. It matches one of mine; that is, the BIOS is set at CA00:0000 (use DEBUG as described above).
If you don't see that, then most probably (a) you have a hosed EPROM or (b) the EPROM is in its socket incorrectly. Look at the image above, make sure your EPROM is oriented the same way and that all pins are in the socket securely--i.e. none are bent.
If no luck there, you probably need a new EPROM with the image burned into it correctly.
I just examined the board carefully. The EPROM chip is oriented the same as the reference image and seated securely. I changed the jumper to use the same address as the reference image and reran DEBUG - again, with all zero flags at all addresses. The only thing different about my board and the one in the reference photo are the 3 small yellow components (resistors?) to the right of the drive capacity jumpers - mine doesn't have those.
Regards,
Mike
Chuck(G)
25k Member
Neither does mine.
Do you have any extra cards with 27256 EPROMs with some valid content? A 27128 or 2764 EPROM might work in a pinch. What we're after is to see if the card decoding logic is squirrely or if the EPROM content itself is zapped.
Do you have any extra cards with 27256 EPROMs with some valid content? A 27128 or 2764 EPROM might work in a pinch. What we're after is to see if the card decoding logic is squirrely or if the EPROM content itself is zapped.
Unfortunately, no. But I have a few other options. One I noticed in an old thread by Anon Cwd' is I might need a 1.44 drive with the jumper (my current Teac is jumperless) to work with the DTK card where I can set it to DS1 - I can get my hands on one of those. The other option is I am awaiting a second HD FDD controller for my 2nd XT which is a VTG FA-100 which I plan to try; I am hoping one of those alternatives will work.
Regards,
Mike
Chuck(G)
25k Member
The DTK card takes a standard floppy cable (A:=twist, B:=flat) and standard PC-configured drives (i.e. second drive select). Your jumperless Teac is hardwired that way.
Your problem is that the add-on BIOS isn't present. You can verify this by using a utility such as Dave Dunfield's ImageDisk to see if it will read a high-density floppy (it doesn't use the BIOS for access). There are also a couple BIOS additions that run as installable device drivers, rather than ROM-based BIOS additions.
Your problem is that the add-on BIOS isn't present. You can verify this by using a utility such as Dave Dunfield's ImageDisk to see if it will read a high-density floppy (it doesn't use the BIOS for access). There are also a couple BIOS additions that run as installable device drivers, rather than ROM-based BIOS additions.
OK, I tried 2M-XBIOS and that didn't work because the system thinks it's an AT with the InBoard/386, so I tried using 2M-ABIOS which loaded with the CONFIG.SYS statement DEVICE=2M-ABIOS A:4 B:1 I13 . It loaded the driver on boot and said my 3.5" A: drive was 1.44 and by B: 5.25" B: drive was 360K which is accurate, but when I try to read any 3.5" disk, 720K or 1.44M, it hangs. Are there any other device driver BIOSs I should try. I am not sure what causes that hang.
Note that when using the drivers I did disable the FDD controller's on-board BIOS. The first time I hadn't done that and my whole keyboard locked up. When I disabled it, then the boot went clean, the 2M-ABIOS loaded with the correct message, and my keyboard didn't lock up, but if I put a disk in Drive A: and it enter the cursor goes to the next line (blank) and just hangs (no disk activity).
Could the problem be related to the cable I am using? The flat IDE cable has 4 connectors - a pair i n the midddle and a pair at the end. Each pair is made up of a 34pin connector and a standard floppy connector. I've connected the 34-pin connector at the end of the cable to the 3.5" Teac 1.44 and the middle one uses the standard floppy connector connected to a 5.25" 360K drive (of course I made sure the red side aligned with pin 1 in all cases).
Regards,
Mike
Last edited:
Chuck(G)
25k Member
I'm a little confused. An IDE (ATA) cable is 40 conductors. A floppy cable has 34 conductors, two on the "flat"section (one for controller and the other for the B drive) and one "twisted" connector for the A: drive. Doesn't that match yours?
Stone
10k Member
I think he has a standard floppy cable with dual connectors, i.e., IDC and card edge for both A: and B:.
SomeGuy
Veteran Member
Given that there seems to be an issue with the BIOS chip, and the machine has an odd configuration, I would skip messing with 2M-XBIOS for the moment. Too many additional variables there. Try using ImageDisk, which does not directly use BIOS, to read/write a high density disk to see if the FDC chip itself is working and then go from there.
Since the drive activates and works fine with low-density media, I doubt the issue has anything to do with the cable.
Since the drive activates and works fine with low-density media, I doubt the issue has anything to do with the cable.
Chuck(G)
25k Member
You know, I offered that same BIOS in this thread and was ignored. I somehow think that the OP doesn't have the means to burn one into a PROM.
...and there's the possibility that even that won't help if there's a fault in the ROM address decoding.
...and there's the possibility that even that won't help if there's a fault in the ROM address decoding.
Phil Saunders
Experienced Member
I had the exact same symptoms - IE a HD drive apparantly locked into Low Density mode no matter what I tried.
Turned out to be that with a 360K and a HD drive on the same cable, the density select line on the CABLE was being pulled low by the 360K drive. Solved by putting a strip of masking tape over pin 2 of the edge connector on the 360K drive. This pin SHOULD be N/C on a low-density drive, but isolating it worked for me!
Turned out to be that with a 360K and a HD drive on the same cable, the density select line on the CABLE was being pulled low by the 360K drive. Solved by putting a strip of masking tape over pin 2 of the edge connector on the 360K drive. This pin SHOULD be N/C on a low-density drive, but isolating it worked for me!
I don't recall if I tried it with only the 1.44MB drive connected to the cable, but I'll give that a try. I'd flash the BIOS is I had a way to do it but unfortunately I don't.
I have a few other tricks up my sleeve yet. One option is to try using a spare SUMO SPI 300 SCSI card I have that also support HD drives, but I hadn't gotten that one working at the time b/c when I installed it it kept searching for a SCSI drive and hung - so I terminated the read SCSI connector with an active terminator but it kept on searching and hung - I assume because it was still looking for a SCSI device or terminator for the internal connector. Well, since then I scavenged a SCSI internal ZIP drive with its own termination pin from another old machine, so I can also try using that SCSI card to connect the 1.44 drive (looking for a spare 50pin F/F internal SCSI cable I have buried away in one of my storage boxes so I can try that path as yet another path.
Regards,
Mike
Chuck(G)
25k Member
That applies to 5.25" drives, as the density select is needed, since the drive can't tell the difference between HD and DD media on insertion. However the vast majority of 1.44M 3.5" drives are configured to use media-select (i.e. the extra hole on the left side of an HD floppy) and pin 2 is NC.
Just a thought, What "XT-IDE" card do you have, one from Lo-tech, Sergey, Or an original ( VCF ) ?, And how comfortable are you in flashing the bios. If you are confident in flashing the bios on the XT-IDE card you could use that as a temporary home for the Floppy controller card bios if you can get a copy from Chuck ?, But it all depends on how confident you are in flashing the XT-IDE card.
Chuck(G)
25k Member
Although the original has a 27256 EPROM in it, the BIOS memory address would seem to say that a 2764 would work just as well.
@mc_mike, if you're in the USA, I'd be willing to burn a copy for you.
@mc_mike, if you're in the USA, I'd be willing to burn a copy for you.
Phil Saunders
Experienced Member
I agree - MOST - but not all. Maybe the drive I had was a very early model, but the drive I had would format a 720K disk to 1.44 if I forced it via the command line, so this implies that the controller COULD switch density regardless of media inserted (of course this resulted in a disk fit only for use as a coffee coaster, but I did it to prove my theory regarding the cable).
Just a thought - easy to try before re-flashing EPROMS and whatever else!