14 Nov
2007
14 Nov
'07
8:52 a.m.
At 11:27 PM 11/13/2007, you wrote:
On 13 Nov 2007 at 22:57, Grant Stockly wrote:
Wait one darned second. There's a lot of confusion here--many
vendors refer to the *data rate*, not the actual clock. Since the
1771 is an FM-only chip, that translates to 2 cells per bit time, or
a 250 KHz clock rate. The frequency of the clock at pin 24 of the
1771 should be 1MHz. If it's 2MHz, it's running at the 8" rate
(500KHz = data rate of 250KHz).
I'm sorry about that! : ) Right now it has a 2MHz crystal to run
the 1771 at 1MHz. I forgot all about the divider...
Grant
FYI:
3.5" disks were never meant to run at 125khz. The
720k mode is 250khz and the 1.44mh is 500khz. The read
amps just may not work well down that low.
Do you think that it would be better if I were to get the Tarbell to
run at 4MHz (250kHz)?