6 Jun
2005
6 Jun
'05
7:55 a.m.
From: "Jules Richardson" <julesrichardsonuk at yahoo.co.uk>
Sent: Monday, June 06, 2005 6:54 AM
On Sun, 2005-06-05 at 17:45 -0700, Eric Smith wrote:
Part of my original point about using 4.77Mhz is that all of the CGA cards I
ever saw had their own crystals and ignored the MB clock.
The fact that the PC used 5Mhz parts but only ran at 4.77Mhz was just a loss
of speed. One of my real peeves about IBM's design.
As far as the 8' disks I always had to get a couple of buddies to help
change disks, the real bitch was the lock down bar or was that holding down
the shift key when typing ;-}
Randy
www.s100-manuals.com
Patrick wrote:
Does that mean that IBM machines running PAL display rates had a
slightly different CPU clock frequency as the main crystal would be
different?
[btw, where did we suddenly get an 8-foot floppy from!?]
If the 8088 has an 8 bit bus and the 8086 is 16 bits, is there a good
reason why it didn't get named the 80816? I'm assuming that's what the
last digit in the number signifies...
cheers
Jules Ok, I don't understand that... Colorburst is
(on NTSC), about 3.58 MHz,
which isn't easy to derive from 4.77MHz. I highly doubt IBM's reason
for using that speed had anything to do with (at least NTSC) video.
Yes, that was the reason. They had a 4x colorburst crystal (14.31818
MHz).
They divided by three for the CPU clock, and by four for the colorburst.