2 Nov
2007
2 Nov
'07
11:03 p.m.
On 3 Nov 2007 at 14:10, Ethan Dicks wrote:
That's like the opposite of what Amiga did to add
2MB (raw) high-density
floppy support to all models - since it wasn't feasible to get the
installed userbase to upgrade their Paula chips, even if C= wanted to
make a new one, they went the other way - the drive spins at half-speed
when high-density media are inserted so that even a 1985 Paula can
keep up with the bitstream.
In the early days of the PC AT, many PC XT wanted the ability to
handle the "new" 1.2MB media. This would have meant replacing the
floppy controller for one that could do the tri-rate (250/300/500
Kbps) trick, but such beasts were expensive (I have a Sysgen
Omnibridge that I use in my XT and it wasn't cheap). Someone (Fred
might remember; my mind is too fuzzy right now) came out with a 1.2MB
drive that would spin down to 180 RPM for high density and 300 RPM
for double-density use. Pretty slick--no need to replace your FDC,
but you get about one-quarter of the read head output voltage at the
lower speed, so performance on the inner tracks wasn't wonderful.
Cheers,
Chuck