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View Full Version : Tandon 360KB (TM100-2a) in modern PC, Formatting problems



mgutzeit
August 6th, 2017, 12:47 AM
Hi @ All,

trying to mount the above mentioned dirve into a "modern" PC. The PC is an IBM Intellistation A Pro (6224). I have installed MS DOS 6.22 on an internal IDE Disk. Then i connect the drive to the internal Floppy Controller, put the right format (5,25 " with 360 KB) in the Bios Setup program. After starting into MS DOS from Hard Drive - I tried to format again a DSDD Floppy (soft sectored) which was successfully formatted in an IBM PC 5150 with exactly the same Tandon Drive.

Now the problems
1. The Drive starts to format the floppy without any error until 72 %. Then it gets scratchy noises (the typical sector not found sound)
2. It formats until 102 % (which i never had seen before)
3. After format it shows that the size available is only 180 KB and with 60 KB in faulty sectors. so it seems to me that the drive is trying to format only one side ?

Surprisingly this happens identical to ANOTHER Tandon Drive (i have two) which is working fine in the IBM PC 5150 also.

I also tried to isolate the Pin 34 which has absolotely no effect.

Does anyone have an Idea ? I think the IBM BIOS is not compatible with that drive even showing this possibility in Bios Setup

lyonadmiral
August 8th, 2017, 12:54 PM
Hi @ All,

trying to mount the above mentioned dirve into a "modern" PC. The PC is an IBM Intellistation A Pro (6224). I have installed MS DOS 6.22 on an internal IDE Disk. Then i connect the drive to the internal Floppy Controller, put the right format (5,25 " with 360 KB) in the Bios Setup program. After starting into MS DOS from Hard Drive - I tried to format again a DSDD Floppy (soft sectored) which was successfully formatted in an IBM PC 5150 with exactly the same Tandon Drive.

Now the problems
1. The Drive starts to format the floppy without any error until 72 %. Then it gets scratchy noises (the typical sector not found sound)
2. It formats until 102 % (which i never had seen before)
3. After format it shows that the size available is only 180 KB and with 60 KB in faulty sectors. so it seems to me that the drive is trying to format only one side ?

Surprisingly this happens identical to ANOTHER Tandon Drive (i have two) which is working fine in the IBM PC 5150 also.

I also tried to isolate the Pin 34 which has absolotely no effect.

Does anyone have an Idea ? I think the IBM BIOS is not compatible with that drive even showing this possibility in Bios Setup

It is compatible with 360k disk drives, but I estimation is that it is compatible with the half height drives and not the full height one.

SomeGuy
August 8th, 2017, 01:50 PM
I encountered a similar problem attaching a Tandon 100-2a to a Kt7a motherboard. The disks and drive worked perfectly on the older machine, but when used on that machine would give random read/write errors on the upper tracks.

I'm afraid I don't recall what if anything I did to resolve the issue (I was repairing an unrelated issue), and I never got to the bottom of the problem. It seemed that there was "noise" coming from somewhere else.

Are you running this drive as the only drive in the system? Or do you have a second drive on the same cable? If you have another drive, perhaps try the tandon all by itself. Also try with and without a terminator resistor pack.

I'd think the 102% would just be confusion from an abnormally large number of bad sectors. Or because it thinks it is formatting 180k, and nobody checked the % value in DOS 6.22.

The resulting 180k format may occur if Format thinks it can not write successfully to the second side. Format may assume you either have a single sided drive or disk and switch to the single-sided (180k) format.

ldkraemer
August 8th, 2017, 01:54 PM
On your IBM Intellistation A Pro (6224) what is the position of the floppy in the BIOS? A: or B:
The cable you are using is a Straight 34 Conductor, or does it have the Conductors 10 thru 16 twisted for two floppy's? Straight or Twisted?
What Position on the Cable is your Floppy Located? Middle or End?
What Jumper is selected for the Floppy Drive Select? DS0: or DS1:?
Are there Two Floppy's on the Cable or Just one? 1 or 2?
Does the Floppy Drive located on the end of the cable have the Terminator RP1 Installed? Yes or NO?

One thing you may not know or realize is that there are two Motor ON Signals 10 & 16. Both are toggled
at the same time to get A: & B: the Motor ON Signal.

The last Floppy on the Cable needs a Terminator installed. If there is only one floppy it is installed on the END of the twisted cable and
the DS1: jumper is closed, so the Drive is set (strapped) for Drive 1, and the twisted cable inverts that for Drive 0:. Additional Floppy
drive is placed on the center connector on the cable also strapped for DS1. It will become B: Drive.

If it's a straight through cable you will need to strap A: as DS2, because Pin 14 is for A: drive select, and plug it in on the END of the cable with
the terminator installed. If using two floppy drives the second one is plugged into the Middle connector and is strapped as DS1 and is
controlled by IBM FDC Pin 12. Just make sure DS0 is NOT selected for A:. See the IBM-SIGS.png below.


I use these TM100-2's on my Desktop all the time, and they work.

Larry


40209 40210 40220 40221 40223

mgutzeit
August 9th, 2017, 01:31 AM
Thanks for all your informations. Very appreaciated. The Bios of the 6224 supports only one Floppy. It is fixed configured as "a:". The Tandon is the only device on the cable. The Terminator is installed. The drive is hooked by the connector with twisted end at the end onf the cable. In the programmable shunt there is a clip in the 3rd left position which is DS1 if i read it correct from the provided graphics. I have two drives of the Tandon and can reproduce exactly the same behaviour with both drives. Ho can i check if the cable is ok ? i doubt it could be simply the cable ?

Retried to attach the fotos

4023040231

ldkraemer
August 9th, 2017, 10:08 AM
The cable to the floppy looks correct. Would there be any chance that some of the Pins in the Connectors
could have been removed when the cable was assembled? You can use a piece of small wire to insert into
the Header end and then OHM to the Edge Connector end.


Do you have a spare ISA Slot in your computer? If so you can get an Adaptec AHA-1522 SCSI Controller and plug into the
ISA Slot. THen disable the SCSI part and just use the Floppy Controller on it. Just make sure it has the Floppy Connector and
the FDC Chip on the AHA-1522,

Do you have the information about the pinout of the Floppy Disk Controller (FDC) for that computer? There has to be something
different about it. It's unlikely it is the Floppy Cable, but it's possible. If you can locate or borrow another cable try it.


Larry

mgutzeit
August 9th, 2017, 02:07 PM
Re-attached the fotos in above thread. The IBM 6224 unfortunately has no ISA Slot. I have a 1542 CF at hand but can't use it in this one (this is intended for my IBM 5162). I'll get a half height drive (360 KB) and another cable in the next days. Will report then if theres is different behaviour. I searched thorugh the HMM of IBM 6224 and the User Guide. In both there is no PIN layout for the Floppy connector. Meanwhile i test the cable with an 1,44 MB Floppy drive. This works w/o any error

ldkraemer
August 10th, 2017, 10:51 AM
The HMM I downloaded states this:
1. If there is a diskette in the drive, verify that:
The diskette drive is enabled in the Configuration/Setup utility program.

Is there such a program to configure the computer for the Floppy?


Larry

mgutzeit
August 10th, 2017, 02:21 PM
Yes. there is... Works fine with the 1,44 MB Floppy with the same cable (by the way - IBM means the "Bios Setup" with the above statement). The HMM shows also clearly that the PC only supports ONE floppy drive. You cannot attach an USB Floppy if you have not disabled the internal Floppy in Bios Setup... Real strange :-). So perhaps i have a perfect mismatch in my try to build a tweener PC with a 6224 from IBM :-( ...

ldkraemer
August 10th, 2017, 04:09 PM
OK, I've double checked Pins 2, 4, & 34 that actually aren't used on the Tandon TM-100 drives. All other signals should be correct if a 3.5" Floppy formats and
works correctly. Pin 10 on the connector of the 3.5" Floppy is DS0 (A:) and that is the same for the Tandon TM-100.

I'm curious when you have the Tandon TM-100 connected and run the Drive if it is spinning at 300 RPM. Those Drives have a paper circle on the Hub that
you can use under a Fluorescent Light to see the RPM rate for 50 HZ & 60 HZ. Is that Hub on the TM-100 spinning at 300 RPM with a 5.25" Floppy inserted?

Is your 3.5" Floppy set to use DISK CHANGE or READY on Pin 34? The Tandon TM-100 does not have this signal.

Thanks.

Larry

Chuck(G)
August 10th, 2017, 04:26 PM
One thing that may be getting in the way is that the TM-100 uses the old 150 ohm pullups, which requires the host to sink a fair amount of current. Some motherboards are incapable of handling this much current. Try replacing the terminator with 1K or 2K pullups and see if it makes a difference.

David_M
August 10th, 2017, 04:45 PM
Since the drive and disk work happily in an XT but not in an AT class machine its probably the head step rate in the AT that is causing the problem.

the IBM Intellistation A Pro was produced at a time when people were moving away from using 1.4M floppy drives. They would have optimised the bios for the faster step rates of the 1.4M drives and half height 5.25" and not even considered anyone would want to run an obsolete full height 360k drive in it.

I doubt the problem is the cable wiring because the drive spins up and steps.

Chuck(G)
August 10th, 2017, 04:50 PM
The easy way to check that is to format and verify using IMD. I believe it allows you to change the step rate. If you want DOS formatting and are running DOS, try a utility like FORMATQM that allows you to specify the step rate.

mgutzeit
August 17th, 2017, 11:24 AM
Had no success with Formatqm. I think the bios really has a problem with such kind of device. It has also not been the cable. totday arrived my Internet order with a HH 5,25 360KB drive. It works without any problems. Also the Floppies are readable and rewriteable in the XT / PC... So now i can go on... Thanks for all of your hints... The HH drive was the solution...