[syslinux] isohybrid and ISO images whose size is not a multiple of 2048 bytes vs. VirtualBox

[Ady]

> 
> Same result as yours.
> 
> 
> Have a nice day :)
> 
> Thomas
> 
 
I was under the impression (apparently the wrong one) that your 
pseudo-code was adding 4 cylinders to the first example, from 132 to 
136, which would be non-optimal. Since I am not a developer, I believe 
you when you say that such jump won't happen :). Perhaps the code will 
be more clear to me when I'll see it included in isohybrid.c (and/or in 
the Perl variant).

I understand the math. Your code is focused on the valid values for the 
amount of cylinders, and my focus was on the padding ranges. Of course 
they are equivalent.

Now, I have a question:  what about the "offset" parameter? How it 
modifies our assumptions and calculations if the "offset" parameter is 
not zero?

For example, in isohybrid.c I see:
 660:     psize = c * head * sector - offset;
and
 1135:	psize = isosize / 512;

among others. There are partial equivalents in the Perl variant.

Since I am not a developer, I am not really asking about the code. My 
interest is about how the "partition offset" parameter ([0, 64]) could 
affect the optimization we have been discussing.

Regards,
Ady.
 

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