VOGONS


First post, by Subjunctive

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I recently acquired a 5150 with floppy drives, and have been endeavoring to get some software onto disks that those drives will recognize.

Most of my previous disk imaging has been for Apple II machines, where you really only have a couple of different formats to deal with, and ADT makes the imaging process itself dead simple in either direction. With the IBM PC it's rather different - there are lots of different disk formats, different types of 5.25" drives, etc. I've learned a lot since I started down this road... but I'm clearly still doing something wrong, because the PC's floppy drive doesn't like the disks I create. The drive itself is fine; it has no issue reading disks that I didn't create.

I'm using ImageDisk, which seemed like the best option. The disks I'm working with are DSDD, but with a lot of them, I'm only use one side. Here are the parameters as I understand them. These rae what I use when formatting disks via ImageDisk, and when writing images.

SSDD/DSDD, single step, 9 sectors/track, 512 bytes/sector, interleave 1:1, data rate of 250 kbps, MFM disk.

And when I use the BIN2IMD utility to create IMD files from raw IMG files, I use ...

160k raw to imd:
BIN2IMD image.img image.imd DM=5 N=40 SS=512 SM=1-8 /1

180k raw to imd:
BIN2IMD image.img image.imd DM=5 N=40 SS=512 SM=1-9 /1

But any boot disk I create from the PC-DOS images I've downloaded, using the above parameters, the PC refuses to boot from: "Boot Disk Failure". It tries to read the disk, stutters for a second, then stops. Like I said, I know the drive itself is fine because I have other disks that it reads with no problem.

What dumb thing am I missing here? Any advice would be appreciated...

Reply 1 of 17, by Scali

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Are you using a DD or a HD drive to write the disks? Because HD drives can read DD disks, but a DD disk written in a HD drive can usually not be read in a DD disk, because the HD heads just are too different, and write an incompatible signal.

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Reply 2 of 17, by Subjunctive

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HD. But according to the ImageDisk documentation, I should be able to:

If the disk was recorded at 250kbps and you are attempting to write with a HD (1.2M) drive, you MUST set the 250->300kbps data rate translation (also, see documentation regarding other compatibility problems).

The first time I tried to write to a disk, it gave me "no data" errors, but then I read the above, set the option within ImageDisk, and it seemed to write successfully.

Reply 3 of 17, by Jepael

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I believe you need to enable "Double Stepping" as HD drive has 80 tracks and DD drive has 40.

But still, HD drives have narrower heads, so they can read disks formatted in DD drive when double stepping, but writing narrow tracks may not be readable with DD drives. And AFAIK writing two narrow tracks with same data cannot be aligned with such accuracy that a DD drive could read it.

So write 40-track DD images in 40-track DD drive. There's got to be some utility that would allow to write disk images over serial port or something.

Reply 4 of 17, by jwt27

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Have you tried the align/test function in Imagedisk? You could try connecting both the HD and DD drive to the same computer, format/write disks on both, and check if they can read each other's disks. I'm basically doing the same thing right now to align all my drives to each other.
If you're writing used DD disks in a HD drive, you're writing a narrow track into an already existing wide track, so you'll have a lot of "garbage" data inbetween tracks which DD drives can still read. Try erasing the disk completely before writing. A good method I found, is to pass a neodynium magnet over the floppy several times in all directions, then hold it up to a crt monitor, and press the degauss button. Disks erased in this way are 100% empty (according to my scope), and should be better suited for HD->DD use.

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Reply 5 of 17, by Subjunctive

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Scali wrote:

a DD disk written in a HD drive can usually not be read in a DD disk, because the HD heads just are too different, and write an incompatible signal.

Jepael wrote:

But still, HD drives have narrower heads, so they can read disks formatted in DD drive when double stepping, but writing narrow tracks may not be readable with DD drives. And AFAIK writing two narrow tracks with same data cannot be aligned with such accuracy that a DD drive could read it.

jwt27 wrote:

If you're writing used DD disks in a HD drive, you're writing a narrow track into an already existing wide track, so you'll have a lot of "garbage" data inbetween tracks which DD drives can still read.

Yep, yep, and yep. Looks like what I'll have to do is replace the HD drive that I've been using with a DD drive. Nuts. Those don't seem to be too common on eBay. 🙁

Reply 6 of 17, by jwt27

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It's not impossible to exchange disks between HD and DD drives.. you just have to make sure both drives are perfectly aligned to each other 😀
The inner tracks are especially problematic, since the (linear) disc velocity is lower here so the signal strength drops too. And an HD drive writes narrow tracks, which appear as weaker signal to a DD drive.

Here's one raw track from a floppy, written in a HD drive, with some files modified by a DD drive:

HsiyY7Y.jpg

As expected, since the HD sectors are half-width, they appear as half amplitude signal to the DD drive.
Same disc, same track, as "seen" by an HD drive:

CX5llgU.jpg

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Reply 7 of 17, by Subjunctive

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Update!

I went ahead and got a DSDD 5.25" drive off eBay - a Qumetrack 142, described as a "working pull" from an IBM 5155.

I connected it to an Aptiva that I keep around for DOS purposes and changed the BIOS setting for the drive to 5.25" 360k. My intention is to use the Aptiva to write images to disks, and then use those disks in my 5150.

So here's what happens now: the drive will give me directories of existing disks... and I can format it from within ImageDisk. But whenever I try to format from DOS, it gives me a track 0 error claiming the disk is unusable. If I try to write an image from ImageDisk, it gives me all sorts of NoAdrMark errors. And something interesting: if I do a del *.*, it gets rid of the files on the disk, but stops just short of returning me to the command prompt, giving me a General Failure. (And yeah I confirmed these are indeed DSDD disks.)

However... the track 0 sensor in the drive is working right, or at least I think it has to be working right, because when I go to the alignment test in ImageDisk, it does report correctly when I step onto, or off of, track 0.

I've reached the admittedly shallow limits of my knowledge. What else could be the problem here? It seems like if it were a dirty head, then even ImageDisk would have refused to format anything... but what do I know?

Again, I appreciate any input you might have.

Reply 8 of 17, by keropi

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I can't add anything of value to the op's problem but I can write 360kb disks on my 386DX's 1.2MB drive and read them correctly on my Acer XT system that has 2x 360kb drives. Both "just files copied with DOS" and rawrite3 for images work for me. Is that pure luck?!

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Reply 9 of 17, by Subjunctive

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Hmm, so here's one possible lead to my problem:

https://support.microsoft.com/en-us/kb/96769

Some hardware manufacturers used earlier versions of MS-DOS to define the capacity of the floppy disk drives on their computers. MS-DOS versions 5.0 and later do not recognize some of these definitions. If your drive doesn't format floppy disks, you must either redefine the disk drive using the DRIVPARM command in your CONFIG.SYS file, define a second configuration for the disk drive using DRIVER.SYS in your CONFIG.SYS file, or contact the original manufacturer of your hardware for a BIOS that supports MS-DOS 5.0 and later.

This makes intuitive sense to me because the thing is certainly behaving like it's some setting that's wrong, not the drive's hardware. I'm running MS-DOS 6.22 on the Aptiva.

Reply 11 of 17, by Subjunctive

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But how? The Aptiva has a 3.5" of course, but would a boot disk from that let the 5.25" be recognized? Remember I've no way of creating new 5.25" disks...

Reply 12 of 17, by alexanrs

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Didn't you quote that MS-DOS 5+ do not recognize some parameters set by outdated BIOSes and because of that has trouble handling some floppy hardware? A MS-DOS 4 bootdisk would not have this issue, and that could format the floppy and copy files to it, no?

Reply 13 of 17, by Subjunctive

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Well, I don't have any boot disks to start with - I'm trying to create one. And I think I'm going down the wrong road anyway - the Aptiva is '96 or '97 vintage and the BIOS itself contains a setting for a 360k drive. So I don't think DRIVPARM or DRIVER.SYS would help...

Reply 14 of 17, by Subjunctive

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Yeah just tried both methods from the MS article, no dice.

Just to confirm that I'm not crazy, I put a variety of disks in the drive and was able to copy all the files off them. Just... refuses to format. Which sucks because the whole reason I got this drive was to make boot disks and other things that the drive in my 5150 is capable of reading.

Reply 16 of 17, by Subjunctive

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You're probably right.

And it seems like my issue has been solved in a totally different way. I put the HD drive back in, and instead of using ImageDisk, I used a self-extracting program that put DOS 2.1 onto a DSDD disk.

The HD drive wrote it to a DSDD disk... and it worked in the 5150.

So, whatever other issues exist with the DSDD drive (and like I said, I think you're right, I think the Aptiva is just too new; this is also evidenced by the fact that when the DSDD drive was installed, the 3.5" drive refused to recognize anything... not sure wtf is going on there), it seems I at least have a boot disk now and I can get the 5150 up to a usable state.

I appreciate everyone's help very much.

Reply 17 of 17, by jwt27

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Have you tried Imagedisk's TESTFDC on the Aptiva with DD drive? At least 250k MFM mode should work...

keropi wrote:

I can't add anything of value to the op's problem but I can write 360kb disks on my 386DX's 1.2MB drive and read them correctly on my Acer XT system that has 2x 360kb drives. Both "just files copied with DOS" and rawrite3 for images work for me. Is that pure luck?!

If you write a disk on the DD drive, then modify some files with the HD drive, can the DD drive still read them...? 😉

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