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Qemu only recognizes Floppy 1440kb format and not smaller 360kb images?!


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#1 davidm71

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Posted 12 March 2018 - 09:53 PM

Hi,

I am trying to create Fat12 images of various sizes using MTools (MFormat) and if the file size of the image is less than 1.44 mb Qemu -fda or -device if floppy fails to recognize the disk image! Will work as an Hda image though. My best guess is that the disk characteristics become non-standard and confuses Qemu. Not sure what is the best way to format the image to get the characteristics needed to be accessed by a PnP option rom as an emulated drive. Using Qemu for time being to test out the code but eventually will have to go much smaller than 1.44 mb!


Thanks

#2 Wonko the Sane

Wonko the Sane

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Posted 13 March 2018 - 10:38 AM

Maybe the issue is not with Qemu, but rather with the BIOS it uses.

 

When it boots the VM uses the hardware that is recognized by the (virtual) BIOS.

 

The floppy driver in itself does support various formats:

https://github.com/q.../hw/block/fdc.c

including the 360 Kb

 

Depending on the Qemu version, it will normally use either SeaBios or PC-Bios, it is possible that the one (or the other) doesn't support that size/format:

 

https://github.com/q.../master/pc-bios

 

Cannot say specifically how to solve the issue, but I believe you can use the 1.44 Mb size for development and then *somehow* have the thing loaded as option ROM "directly", similarly with what is done for PxE ROM's and similar, example:

http://etherboot.org...romburning/qemu

 

Also maybe it depends on the specific build/version of Qemu. :unsure: , older versions used the BOCHS BIOS, and for some formats an ooption "-no-fd-bootchk" was needed, if I recall correctly.

 

:duff:

Wonko






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