Philip Blundell writes:
> Previously, I wrote:
> >It seems to me that the code we use for floppy pseudo-DMA at the moment is
> >unnecessarily complicated. [...]
>
> Russell, you mentioned that you thought whole-track reads might fall foul of
> this. By my calculations the maximum buffer size with my code is 0x18004/4
> or 24577 bytes. If you extrapolate this to an 80-track double sided disk you
> get a capacity of 3840 kilobytes which is (as far as I know) way beyond
> what any drive fitted to Acorn equipment is capable of. In fact the Acorn
> PRMs give the maximum "actual workable track length" as 12312 bytes.
Careful how you refer to a track and a cylinder. A cylinder consists of
two tracks on a two headed drive. The disk controllers are capable of
automatically changing 'sides' of the disk. Hence, for an 80-cylinder
disk, the maximum capacity that would be supported by this is not 3840KB
but 1920KB. (as specified in the A5K TRM incidentally). Since this
format would require a data rate of 500kbps, it is just within the
drive specs.
_____
|_____| ------------------------------------------------- ---+---+-
| | Russell King [EMAIL PROTECTED] --- ---
| | | | http://www.arm.linux.org.uk/~rmk/armlinux.html / / |
| +-+-+ --- -+-
/ | THE developer of ARM Linux |+| /|\
/ | | | --- |
+-+-+ ------------------------------------------------- /\\\ |
unsubscribe: body of `unsubscribe linux-arm' to [EMAIL PROTECTED]
