kikendo wrote on 2020-06-16, 22:11:

OK I am more confused than before. I did a lot more tests, and I managed to format a bunch of 360KB disks, but not all. Also the […]
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OK I am more confused than before. I did a lot more tests, and I managed to format a bunch of 360KB disks, but not all. Also the only 1.2MB disk I have, I couldn't format (same error, track 0 unreadable). I made a MS-DOS 6.22 boot disk which seemed more successful at formatting disks than the Windows 98 DOS boot disk I had before. Could it be that Windows 98 had something to do with this, too?

The weird thing is that the disks that I can't write to on the PC I can write to on my C64.

I think the drive is fine, but maybe it's more sensitive to media on the verge of bit rotting, which might be read OK but losing density to be written on.
I would have to buy a box of new old stock 2HD disks to do more tests, but for now I feel like I spent way too much time with this unit.

Are the disks that work only on your C64 single-sided ?

Not that it will help right now, for Googlers of the future I'll note that I just wrote an image to a 40 track 360k 2S-2D disk with a Panasonic JU-475-4 (1.2MB drive). It then booted and read and wrote on an Epson SD-521, 360k-only drive in an 8088. So I can attest that those particular models seem to work ok for this purpose

There is no solution and best way to do this is obtain 360K floppy drive and use this. The magnetic flux on 360K and 1.22MB floppy disks are completely different also.

Or obtain 1.22MB floppy disks and use it only to store stuff on 1.22MB floppy drive. And read *only* the 360K disks on 1.22MB drive.

Cheers,

kikendo wrote on 2020-06-16, 22:11:

OK I am more confused than before. I did a lot more tests, and I managed to format a bunch of 360KB disks, but not all. Also the only 1.2MB disk I have, I couldn't format (same error, track 0 unreadable). I made a MS-DOS 6.22 boot disk which seemed more successful at formatting disks than the Windows 98 DOS boot disk I had before. Could it be that Windows 98 had something to do with this, too?

Yes ! DOS 7.1 (Win98) is a bit different for working with floppies than real DOS (5 or 6.x) or DOS 7.0 (Win95). It is a known problem for some of us....
https://support.microsoft.com/en-us/help/1400 … gnized-by-windo

did you clean the heads yet? That would have been the first thing I tried

darry wrote on 2020-06-16, 22:15:

Are the disks that work only on your C64 single-sided ?

No, they were all 2SDD. Also I am using a 1571 and formatting full double sided.

Horun wrote on 2020-06-16, 23:46:

Yes ! DOS 7.1 (Win98) is a bit different for working with floppies than real DOS (5 or 6.x) or DOS 7.0 (Win95). It is a known problem for some of us....
https://support.microsoft.com/en-us/help/1400 … gnized-by-windo

OK then I was running into that trouble on the Pentium II setup I guess! Good to know.

maxtherabbit wrote on 2020-06-17, 00:47:

did you clean the heads yet? That would have been the first thing I tried

Yeah, I cleaned the heads thoroughly.

pentiumspeed wrote on 2020-06-16, 23:17:

There is no solution and best way to do this is obtain 360K floppy drive and use this. The magnetic flux on 360K and 1.22MB floppy disks are completely different also.

As I wrote above, I also tried a 1.2MB disk with similar results.
And I already managed to format 360KB disks on the 386, just not all of them (using format /4)

This might sound strange, but in desperation when this happened to me, I opened the disk drive, and manually moved the heads up from their default position. Then I used the disk by formatting one (with the cover off, so I could see the heads in operation). After a couple of times of letting the heads move to their default position, and moving them back up manually., I was able to format the disk successfully, where previously the format would fail, either at the start, or at the end.

Note, this happened to me TWICE one one disk drive, and both times, this "solution" fixed it.

maxtherabbit wrote on 2020-06-17, 00:47:

did you clean the heads yet? That would have been the first thing I tried

What's the best technique to clean these old 5.25 heads?

Ron

babtras wrote on 2020-06-16, 22:29:

I'll note that I just wrote an image to a 40 track 360k 2S-2D disk with a Panasonic JU-475-4 (1.2MB drive). It then booted and read and wrote on an Epson SD-521, 360k-only drive in an 8088.

Can you please explain exactly how you did this? I have the exact same JU-475-4 drive connected to Greaseweazle, and am trying to image a disk to read in a Leading Edge Model D 8088, and I can't get it to work. Did you change any jumpers on the JU?

If you are using HD drive to write to DD media (or HD media but only 40 tracks) try erasing the floppy first. You can use a permanent magnet or do something like this:

gw.exe erase --drive %DRIVE% --tracks "c=0-83:h=0-1" --fake-index 101rpm --hfreq

If your GW software is v1.10 or newer than you use can --revs=N (with N=2 or 3) instead of --fake-index

Do you have to use double step mode, set pin 2 high/low, or set the BX or 1M jumper?

copper wrote on 2023-08-08, 12:13:

Do you have to use double step mode, set pin 2 high/low, or set the BX or 1M jumper?

Yes, you have to use double-step when writing 40 tracks on 80 track drive. No matter what media is used.

Pin 2 needs to be set L if your drive is dual-speed, since DD floppies rotate at 300rpm and HD ones at 360rpm. That being said if your drive does not support 300rpm, or is not configured for it, there should be an option to switch to 300kbps write rate instead of 250. I've never used it, my drive does switch speeds. Another possibility would be to add extra def to diskdefs.cfg (for example copy ibm.360 to ibm.360.hd and change rate = 250 to 300, then just use --format "ibm.360.hd" in the command line).

Or you could try to convert the image offline to different bitrate. Frankly a lot depends on what you are trying to write, is it a correct DD image done at 250kbps at 300rpm? Or 300kbps at 360rpm? If the dump itself was not corrected for speed and/or sampling rate you might need to use different settings to write it back. Or just redump again.

Note, when writing you should be using precomp (--precomp "type=mfm:0=250"). The floppy should work even without it but why make it difficult for the floppy drive on target machine to read the media.

It is working on my Panasonic JU-475-4, thanks to you. I can write a 360kb disc from my 1.2mb drive like so:

BX jumper set (as per https://wiki.applesaucefdc.com/doku.php?id=dr … panasonic_ju475)
Double-step = 2
Precompensation = "type=mfm:0=250"
5.25 Set Pin 2 = Low