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Using 3.5" drives with the SNUG BwG

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Last night I went through a torrent of hardware swapping and hours of troubleshooting. I recently picked up a Sony MP-F11W-2Z 720k floppy drive with the intention to use it either in my TI* or as a replacement mechanism in my Commodore 1581.

 

But I ran into a problem. Connected to a CoCo2 the drive works perfectly fine: it will format a disk and use it. However, when connected to the BwG the drive will format but fails verifying sectors starting at 720, which is at roughly 180k of a 360k format. I connected a Panasonic JU-257 (1.44MB drive) and get the same results with the BwG. Other drives produce the same results. As expected, the drive head does not traverse the entire disk surface.

 

FWIW, the BwG and the CoCo's FD-501 both use the WD1773.

 

I may be over-thinking it but my first thought was "precompensation." Seems a bit of a stretch.

 

Can anyone steer me in the right direction here?

 

* Understanding, of course, only 360k of the disk will be usable.

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Maybe Richard Bell will chime i here. I have been using a BWG with a pair of 3.5" for a number of years. In fact, I have used a variety of Sony, TEAC, and other manufacturers as well. I don't know what to tell you but I think there is a list of drives known to work with a TI (the BWG is essentially a CorComp/Atronic clone). You might check Schmitzi's lists to see if he has included it somewhere. I do know that not all 3.5" 720K drives work with TI controllers.

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Do some additional testing to see where/when the failure begins. I assume this is with a TI system, not a Geneve. A Geneve, you should have been able to get 80 tracks. A TI system, unless the DSR eprom and/or dip switches are set to 80 track, you should be only able to do 40 tracks. I just have no experience with the BWG to know if 80 tracks is possible on a TI system.

 

1). Format SS/SD and confirm you get 90K without issue.

2). Format SS/DD and confirm you get 180K without issue.

3). Format DS/SD and confirm you get 180K without issue.

4). Format DS/DD and confirm you once again get a failure at 360K.

 

If no problem with Step 2, then you are getting double density with no issue. If the problem begins at Step 3, then you have something going on with side 2 of the disk.

 

As far as I know, you do not want to format a disk DS/QD (80 tracks) unless the DSR eprom supports 80 tracks.

 

Beery

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Precompensation is typically used for hard disks. It means that the write signal is shifted by a little degree to compensate for the tighter packing of sectors towards the spindle. A similar effect is related to reducing the write current for hard disks. I think for SD and DD there is no need for precomp.

 

The 720K issue rings a bell. The problem is that the controller must calculate the cylinder and head, given a sector number only.

 

The TI track scheme is to write on side 0 (lower side) inwards, then switch to side 1 (upper side) and continue writing outwards. PCs typically use a side swap scheme (side 0 cyl 0, side 1 cyl 0, side 0 cyl 1, side1 cyl 1, ... side 0 cyl 39, side 1).

 

If the DSR (not the controller; it does not care) does not know that you have 80 tracks, it will falsely calculate the coordinates.

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It is usually much more simple than that. If the disk structure/ drive capabilities are not compatible with a TI type controller (i.e.TI, CorComp, Myarc, BWG) then the disk will not properly initialize or verify. TI type controllers require a specific disk drive type to work properly as well as a proper disk (ex. HD disks will not work on the TI nor will some disk drives)..

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I have had good luck doing DS/DD on a corcomp card with 3.5" 1.44 drives I just use the 720k disks and only format them to ds/dd I can also format a 1.44 disk by covering the HD hole on the disk, but I haven't tried reading those disks on another TI they do seem to read fine on my Geneve with a 1.44 drive and a HFDC. Also there is an 80 track mod for the TI controller to format that disk 80 track, unfort it's only DS/SD 80 track..

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Well, I am armed with the lists Bob has given me, so I will compare those to the drives I have. This is not on a Geneve.

 

What is so frustrating is two different computers, both with the WD1733, yield different results. I have a stack of about a half-dozen HD drives consisting of Alps, Newtronics/Mistsumi, Panasonic, Samsung, and Sony. These all work on the CoCo2 no problem. I can format DD disks, which includes a verify afterward, and read them between each other. Same with the DD Sony. Now, this computer only uses 35 tracks, but it uses them without issue. As expected the head only traverses half the disk.

 

On the TI I tried the DD Sony and the HD Alps. A DSDD format completes its 40 track run, again covering only half the surface of the disk. But during the verify the head steps 40 tracks but only reads 719 sectors. I can see it counting 18 sectors on each step. But that does not seem correct: with 256 byte sectors it should be 18 sectors per side per track, 36 sectors per cylinder, meaning it should read 36 sectors before stepping to the next track, right? Or, per mizapf above, it should be reading 18 sectors each up to 40 tracks, then switching to side 1 and reading back to track 0, which leads to the question of why is side 1 not working.*

 

Now, relating back to the CoCo2, it turns out the RSDOS format is only single-sided. That is a huge face-palm as looking right at the FB-501 drive you can see one head and a pressure arm above the head. DOH! The physical format is the same as the TI's but with fewer tracks in use: 35 tracks, 18 sectors, 256 bytes per sector, giving 157.5k formatted capacity including the directory track. Apparently I would need OS9 to use the full drive capacity, and I ain't about to go down that rabbit hole as I am working to unload this CoCo onto someone who will appreciate it.

 

I will try lower settings to see how they format. I suspect that formatting SSDD will work given the results with the CoCo, but that will just be more frustrating if so.

 

* I may have an answer for this but it require even more disassembly of my PEB. The fingers on the external drive connector of the BwG are terribly corroded. It just might be possible the side 1 connection is bad given how the transmission between controller and drive works, and I believe that no signal from the controller on the SS pin would produce a head-0 select signal in the drive at all times.

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Soaked the fingers in some electronics cleaner and gave a good fiberglass pencil scrub. Lo and behold everything works as expected. Thanks for the indulgences, fellas. I will at some point this weekend try out some drives to augment the lists Bob sent me. I am not certain I would have figured out the ultimate resolution had it not been for that CoCo and mizapf's details on the TI physical disk layout.

 

Now if I just could get the DSR modified for 80 tracks :)

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I just found the picture I once drew about the sector location. The numbers are sector numbers (DSDD40).

 

From this you can easily find the formula to convert the (linear) sector number to a (C,H,S) triple (cylinder, head, sector).

post-35000-0-24809100-1517705476.png

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Hey, has anyone heard of a break-out box for floppy cables? If there is no such beast in the wild I am thinking about rigging one up.

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Well, I am armed with the lists Bob has given me, so I will compare those to the drives I have. This is not on a Geneve.

 

Hi, thx for using my lists :lust: But please remember that I am not errorfree :-D

 

So, I just made actual PDFs from what I have, just to be sure for latest versions:

 

 

pdf.gif TI-99-4A_KB-FLOPPY-FORMATS-v1.10.pdf 28.83KB 32.584.689 downloads

 

pdf.gif TI-99-4A-FLOPPY-DRIVES-TI-99-v1.12a-ALL.pdf 40.72KB 5.397.899 downloads

 

 

post-41141-0-78724700-1517915574.jpg

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Soaked the fingers in some electronics cleaner and gave a good fiberglass pencil scrub. Lo and behold everything works as expected.

 

If you can read the label on your BWG EPROM and the label on your PAL what version does it show?

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The 3.5" drives all run 300RPM. A 5.25" will run 360RPM if it thinks it should be in HD mode, unless you can force it otherwise. I have been able to do that with the TEAC FD-55GFR, but no matter what I do the dual-drive TEAC FD-505 will not run 300RPM. I even tried swearing at it in a couple different languages. No go.

 

I have already reassembled my stack of systems (A4000 on top of a 128D on top of the PEB,) so it may be a while before I take a look at the BwG PAL... unless compelled by the possibility of an 80-track mod.

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If you can read the label on your BWG EPROM and the label on your PAL what version does it show?

 

EPROM: BWG 1.18

PAL: BWG V4.0/8.1.1999

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EPROM: BWG 1.18

PAL: BWG V4.0/8.1.1999

 

Yes, that's the latest versions that I know of.

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Yes, that's the latest versions that I know of.

 

I love this card... just want 80 tracks :)

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A 5.25" will run 360RPM if it thinks it should be in HD mode, unless you can force it otherwise.

 

Pin 2 on the Shugart bus is named DENSEL and goes from the controller to the drive for selecting DD or HD, as I found in the Floppy User Guide [Haardt, Knaff, Niemi].

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Pin 2 on the Shugart bus is named DENSEL and goes from the controller to the drive for selecting DD or HD, as I found in the Floppy User Guide [Haardt, Knaff, Niemi].

 

Right, which I have done either by manipulating the DENSEL line, or setting a strap on the drive. Sometimes you can invert the signal, other times you can override it, just depends upon the drive. Some drives, however, completely ignore the setting, like in the case of 5.25" mechanisms which are part of the combo drives.

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