10 Nov
1999
10 Nov
'99
12:06 p.m.
ard(a)p850ug1.demon.co.uk (Tony Duell) wrote:
Hi Tony
If this is true, it looks like it is possible to work
wonders with this chip ;) The reason for doing DOS compatable
disk is that it makes transfers of info a little easier.
Dwight
Another
factor, the sectors for DOS formatted disk are
512 bytes long. Any loop that only does 256 won't make it.
It would need to be formatted with more wasteful 256 byte
sectors. This has been a good line of thought ;)
Is this a problem? Firstly, who says you'd use an MS-DOS format -- the
CoCo uses 256 byte sectors for virtually everything, and I'd suggest
keeping to that on the HD disks, just having more of them. As to being
more wasteful, well, MS-DOS 360K (and 720K) disks fit 9 512byte sectors
on a track, the CoCo fits 18 256byte sectors. Looks the same to me.
And the 6809 index registers (X, Y, etc) are 16 bit registers. The loop I
posted (and the ones others have posted) will transfer 512 bytes if you
want them to. Whether there's a speed penalty when you cross a 256 byte
boundary I don't know -- I don't remember anything like that in the 6809
instruction set, but it's been many years.