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ImageDisk refuses to work on Turbo XT

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First post, by wbahnassi

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Hi. I'm trying to run Dave Dunfield's ImageDisk program on my Turbo XT, but during initial loading it always hangs for a few seconds then gives a General Error Reading message.
The machine has a Juko mobo, V20 12MHz CPU, 640K RAM, no HDD, two 360K 5.25" drives, loading straight from a clean MS DOS 3.3 disk in drive A, and ImageDisk runs from drive B.

The floppy containing ImageDisk is fully ok, and I can DiskCopy it fully without errors, so it's not bad media nor bad contents. MS DOS fully reads the disk's contents without issues. The same ImageDisk files also work fine on a more modern machine, so the files are complete and not missing anything.

I've run out of ideas on what to try further. I believe the program should work on XT as it's mentioned in the readme file. Not sure what's wrong with my setup though...

Attachments

Turbo XT 12MHz, 8-bit VGA, Dual 360K drives
Intel 386 DX-33, TSeng ET3000, SB 2.0, 1x CD
Intel 486 DX2-66, CL5428 VLB, SBPro 2, 2x CD
Intel Pentium 90, Matrox Millenium 2, SB16, 4x CD
HP Z400, Xeon 3.46GHz, YMF-744, Voodoo3, RTX2080Ti

Reply 1 of 3, by Jo22

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Some Turbo XTs have issues with floppy drive access in Turbo mode.
That's why they have a "slow disk" setting in the Turbo utility.

Re: Unique (Juko ST) UX Turbo XT Mainboard - utility diskette

Not sure if that's the issue here. 🙁

"Time, it seems, doesn't flow. For some it's fast, for some it's slow.
In what to one race is no time at all, another race can rise and fall..." - The Minstrel

//My video channel//

Reply 2 of 3, by wbahnassi

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I'll see what options are available with TURBO.COM.

But toggling off the hardware turbo button doesn't make a difference in this case. And even if I don't, the machine seems to automatically toggle it off during disk access. Why I say that is because the Turbo LED will turn off during disk accesses, looking kinda like an HDD indicator, but for floppies this time.

Now why I don't think this is the issue is because I never had access errors on any other programs or DOS work. They all work fantastic.. only IMD.COM is sad..

Turbo XT 12MHz, 8-bit VGA, Dual 360K drives
Intel 386 DX-33, TSeng ET3000, SB 2.0, 1x CD
Intel 486 DX2-66, CL5428 VLB, SBPro 2, 2x CD
Intel Pentium 90, Matrox Millenium 2, SB16, 4x CD
HP Z400, Xeon 3.46GHz, YMF-744, Voodoo3, RTX2080Ti

Reply 3 of 3, by DaveDDS

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ImageDisk accesses the FDC hardware directly and in some fairly non-standard ways.
You really need a fully NEC 765 compatible AT FDC for it to work properly.
* This also means that any BIOS settings etc. won't have any effect on it!

It *may* work on some PC/XTs, but since those do NOT support high-density
disk formats, the FDC only has a data transfer rate of 250kbps, and therefore
you MUST use the command line option: LR=250
to keep IMD from attempting to set a 300kbs rate.

And unfortunately, many (most) PCs have more limited FDC hardware, as they were
never intended/designed to work Single-Density or other characteristics of many
non-PC floppy disk formats (especially classic ones which is the environment IMD
was created for).

In the PC world, BIOS and a myriad of "windows drivers" isolate the FDC quite
effectively from application software - so lots of factors about the FDC hardware
can be different, yet those systems still work ok in these environments with "officially
supported PC" disk formats!

The real "trick" to using IMD effectively is to try lots of different systems,
and fine one with a "good" FDC.

If all you want to do is backup/restore PC format disks, you can use my
earlier XDISK tool which uses DOS/BIOS to access the floppy drive.

Dave - Author of ImageDisk

Dave ::: https://dunfield.themindfactory.com ::: "Daves Old Computers"->Personal

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