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Old 12 June 2017, 16:21   #1
mark_k
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Join Date: Aug 2004
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Extended ADFs, PAL vs NTSC

One change in WinUAE 3.4.0b6 was this:
- If extended ADF's track space is smaller than write length, ignore first bits in sector buffer (it is most likely part of the gap).

That should prevent disk corruption when using extended ADFs which were created on an (emulated) PAL machine, on an emulated NTSC machine. [The slightly-higher clock speed of NTSC machines means track lengths are longer.]

That probably works fine in the usual case where an entire track is written at once using DMA. However...

I recently installed Mac System 6 from extended ADFs in A-Max emulation with an NTSC machine. I left the files write-enabled, and during the Mac boot process these lines were in the log:
Disk decode: sector 0 header: 00020008 00020000 00000000 44014401
not an amigados track 0 (error 2), writing as raw track
disk raw write: image file's track 0 is too small (12668 < 12798)!
Disk decode: sector 0 header: 00020008 00020000 00000000 44014401
not an amigados track 0 (error 2), writing as raw track
disk raw write: image file's track 0 is too small (12668 < 12798)!
Disk decode: sector 0 header: 00020008 00020000 00000000 44014401
not an amigados track 0 (error 2), writing as raw track
disk raw write: image file's track 0 is too small (12668 < 12798)!


Having those lines in the log may not be a problem due to the above-mentioned change. But later in the Mac OS install process, I saw this:
Disk decode: checksum error on sector 0 header
And the emulated Mac showed a dialog saying "That disk is unreadable."
So it seems the extended ADF was corrupted by the writes.

Is there any easy way to increase all track lengths in a created-on-PAL extended ADF, to allow it to work properly when used on an emulated NTSC machine?


Edit: It turns out I had floppy drive speed set to turbo which may explain the error I saw.

Last edited by mark_k; 12 June 2017 at 16:37.
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