5 Apr
1999
5 Apr
'99
6:03 a.m.
According to the jumper settings on the 5150, it
appears that 4 floppy
drives can be connected to the computer. How is this possible? I'm
guessing 2 internal, and two external, but there's only one connector for an
external drive, so it would only allow 3 drives.
Or is there a special controller that has dual external ports?
The external connector is electrically quite similar to the internal
connector (which supports two drives).
You will need to make a cable with a 37 pin male connector, similar to
your internal cable. Typically, that would include a twist, but there are
ways around that. The pin-out of the cable (Tech Ref p1-182):
Unused 1-5
Index 6
Motor Enable C 7
Drive Select D 8
Drive Select C 9
Motor Enable D 10
Direction 11
Step Pulse 12
Write Data 13
Write Enable 14
Track 0 15
Write protect 16
Read Data 17
Side Select 18
Ground 20-37
Because of the difference in how pins are numbered on D connectors v dual
row headers or card edges, that may seem completely scrambled. But if you
sketch it out, you'll see that you can get away with crimping a 37 pin D
Male onto an ordinbary PC drive cable. (BUT, align pin 34 of the cable
with the 19/37 end of the D connector!!)
If you make up such a cable, then jumper your external drives as "B:",
just like you do for internals.
In addition, if you want to do it "right", turn off positions 7 and 8 of
the 5150 configuration dip switch, so that the PC will know that it has 4
floppies. Hard drive letters, etc. will then begin at E:. Otherwise,
with DOS >= 3.20, you could access the external drives with use of 2
inclusions of DRIVER.SYS (/D:2, and /D:3), which will insert the drive
letters for your extra floppies AFTER your hard drives, etc.
--
Fred Cisin cisin(a)xenosoft.com
XenoSoft http://www.xenosoft.com
2210 Sixth St. (510) 644-9366
Berkeley, CA 94710-2219