On Mon, 12 Jun 2000, Greg Woods wrote:
>
> Alexander Clouter wrote:
>
> > due to microsofts infinite wisdom dos (and so windoze) has trouble
> > handling more than 1024 cylinders (if I remember correctly).
>
> Much as I love a good M$-bashing occasionally, I don't think this is
> Microsoft's doing. The 1024 cylinder limit was in the original design of
> the PC BIOS. Those engineers just couldn't see that anyone would ever
> have a 30GB disk drive on a PC :-)
>
> On most PC's, running any kind of modern operating system (including
> Windoze), the 1024 limit only applies at boot time. Whatever program is
> loaded at boot time must not be stored beyond cylinder 1024. I am told
> that there are some newer BIOS's that can play games with the disk
> geometry and translate block and cylinder numbers on the fly, to make it
> look like the disk has a different geometry than it actually has, and
> get around this limitation. But that is a function of the BIOS, not the
> operating system.
>
actually from what I've read the old BIOS indeed couldn't use do more than
1024 cylinders however that was easily changed. The problem lay in how
MS-DOS calculated the amount of disk space available for using
CHS. However due to a useful feature more than 1024 cylinders could not
be identified. To overcome this problem LBA (or something like it) was
used to translate a 'virtual' CHS to real CHS. This is usually done by
the BIOS however sometimes a software patch instead had to be used
(causing a slight performance hit).
Alex
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