On Fri, 18 Apr 2003, Al Hartman wrote:
> A rule of thumb I use, but I won't swear is
> universal... Is the LED color. USUALLY... Red LED
> signifies 360k/180k Drives, and a Green LED signifies
> 1.2mb Drives.
Like the faceplate color, that is one that TENDS to be correct, but with
exceptions. Some of the earliest 1.2M had red LEDs, andsome of the later
360K drives had green. But it would work for a rough sort, followed by
confirmation by model number.
> And I also think that as for IBM Drives, the 360k at
> one point were made with and Asterisk molded into the
> front case. I could have this reverse. But, I seem to
> remember some discussion (perhaps here) that someone
> thought it was odd that IBM would start adding the
> asterisk to 360k Drives, hence having some with and
> some without, rather than just making all 1.2mb drives
> with asterisks.
> I may have this one reversed though.
No, YOU have it right; IBM did it wrong. Once there were two similar
drives, there was a need for visual identification. The RIGHT way to do
it would have been to put the added emblem on the NEW type, so that all of
the old ones would already be correctly labelled. OR make two different
emblems, so that all emblemed drives would be labelled.
> But, I've used the LED color as a good indicator for
> years.
Glad it's worked for you, but there ARE exceptions. The incorrect door
handle one worked for somebody (who had simply switched brands of drives
at the same time that they switched from buying 360K to buying 1.2M)
> Also, if you look at the jumpers on the logic board,
> near the drive select jumpers... A 1.2mb drive should
> have a Speed Select Jumper (SS) to select High speed
> Data Transfer to work on AT-Standard Floppy
> Controllers, and low speed (for what? I don't know...
> Maybe to work on an 8in Drive Controller?)
NO!
At least a third of the 1.2M drives do NOT have a speed select. It is for
whether the drive changes speed 300 v 360 RPM, NOT for data transfer
rate. The data transfer rate of a 1.2M at "high" density IS the rate of
an 8" DSDD. The two are indistinguishable, unless you count 77 v 80
tracks.
> So, that's another indication of whether the drive is
> high or low density.
If a drive does both 300 RPM AND 360 RPM, then it is 1.2M
If a drive supports both 300 and 360 RPM, then the controller needs only
250K and 500K data transfer rates. (Plus 125K bits per second if you want
to do 5.25" FM (150K bits per second with single speed 1.2M drives))
If a drive only does one speed, then it could be a 360K drive, OR it could
be a 1.2M that expects the controller to handle the difference. The IBM
AT controller did 250K, 300K, and 500K bits per second data transfer
rates, and used single speed drives.
If the single speed is 300 RPM, then it is a 360K drive.
If the single speed is 360 RPM, then it is a 1.2M drive.
--
Grumpy Ol' Fred cisin_at_xenosoft.com
Received on Sat Apr 19 2003 - 13:47:00 BST