Syslinux - Jul 2014 - Possible memdisk issue

From: Ady, Tue, 8 Jul 2014
> [...] every document related to newmkfloppyimg.sh
> specifically recommends adding:
>   floppy c=$CYLINDERS s=$SECTORS h=$HEADS
> to the MEMDISK arguments.
Good advice. As it turns out, according to the memdisk output, it is 
already correctly determining CHS. Explicitly specifying the values 
doesn't seem to have an effect.
> You might also want to add "raw" too.
I tried "raw" and "edd", the infinite looping still occurs.
> There is a chance the resulting floppy image is not adequate
> anyway, but I have not tested it.
That could be. Here are the results of more testing to isolate where 
between 8MiB and 9MiB the problem surfaces, and to lend support to the 
hypothesis that there is a definite transition (i.e., everything below a 
certain size will work, everything above a certain size fails):

fdos_8000KiB works
fdos_8125KiB works
fdos_8180KiB works
fdos_8192KiB works (8MiB)
fdos_8200KiB works
fdos_8202KiB works
fdos_8203KiB works
-----------------
fdos_8204KiB loops
fdos_8205KiB loops
fdos_8208KiB loops
fdos_8215KiB loops
fdos_8250KiB loops
fdos_8500KiB loops
fdos_9000KiB loops
fdos_9216KiB loops (9MiB)

Question: what's special about the transition from 8203KiB to 8204KiB? 
Both have CHS=8/64/32 and both involve a fractional end cylinder.

Alex

On 07/08/2014 03:05 PM, Alexander Perlis wrote:
> 
> Question: what's special about the transition from 8203KiB to 8204KiB?
> Both have CHS=8/64/32 and both involve a fractional end cylinder.
> 
Fractional cylinders with floppy disks is almost certainly a very bad thing.

	-hpa

Alexander Perlis schreef op 9-7-2014 00:05:
> Question: what's special about the transition from 8203KiB to 8204KiB?
> Both have CHS=8/64/32 and both involve a fractional end cylinder.
Can you test the images at [ http://bootcd.narod.ru/images_e.htm ] ?
No idea how these bootdisk images were created, but they're supposed to 
work ( see http://bootcd.narod.ru/fd700000_e.htm )

Bernd

On 07/08/2014 05:55 PM, H. Peter Anvin wrote:
> On 07/08/2014 03:05 PM, Alexander Perlis wrote:
>>
>> Question: what's special about the transition from 8203KiB to
8204KiB?
>> Both have CHS=8/64/32 and both involve a fractional end cylinder.
>
> Fractional cylinders with floppy disks is almost certainly a very bad
thing.
>
Agreed, but that doesn't appear to be the issue here. Fractional 8203K 
FreeDOS does work, yet larger values, including non-fractional ones, do not.

Alex