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ADDING A SECOND (EXTERNAL) HARD DRIVE TO THE TANDY 1000HD
The Tandy 1000HD comes with an internal 10 megabyte drive and the Western
Digital WD1002S-WX2 controller board. This controller board is capable of
handling two hard drives. If you have a 1000HD and wish to add a second hard
drive to the system, it is possible, but you have to know how to do it. This
document will detail the necessary steps.
First, you must make a new set of cables for the hard drives. Each hard
drive uses a controller cable and a data cable. The controller cable is a 34-
lead ribbon with a 34-pin dip connector at one end. The data cable is a 20-lead
ribbon cable with a 20-pin dip connector at one end. The cables in the 1000HD
connect to the controller board with the dip connectors, and to the hard drive
with card-edge connector. You have to determine first what kind of connectors
you will need with the external drive. Some drives use DIP connectors, others
use card edge connectors.
The data cable for the external hard drive should be at least three feet
long, to allow it to pass out of the 1000HD case to the external drive. The
controller cable should be 8 to 9 inches longer than the data cable. You will
need to fasten two connectors on the controller cable in addition to the first
34-pin DIP connector. The first one should be a 34-pin card edge connector and
should be placed approximately nine inches from the dip connector which fastens
to the controller board. Attach this connector so that it faces the OPPOSITE
direction from the controller connector. Then, at the other end of the
controller cable, attach the connector for the external hard drive. Be careful
in making up these cables; a short in either cable could destroy the controller
board!
Figure 1 -- Controller Cable diagram
(2)
__
(1)||==========||=============================||(3)
~~ ~~
|----9 in.---|----------36 in.--------------|
legend: (1) DIP connector to WX2 controller board
(2) card edge connector to internal HD, facing in
opposite direction from (1)
(3) connector to external hard drive
Remove the WX2 controller board from the 1000HD by removing the fastening
screw at the rear wall and lifting the board straight up. Carefully remove both
cables from the board and lay the board on a flat surface component side up,
with the rear metal bracket to your right. Look carefully at the right side of
the board, near the metal bracket. You will see a jumper block marked SW1, with
8 positions. Positions 2, 3, 4 and 5 (numbers AS MARKED on the board) should
have jumpers. The positions are numbered 1 2 3 4 8 7 6 5.
Positions 1 and 2 tell the controller board the capacity of the internal
drive. Position 2 jumpered means a 10-megabyte drive with 306 cylinders and 4
heads which is the configuration of the internal hard drive.
Positions 3 and 4 determine the size of the SECOND (external) hard drive.
They are both jumpered. This defines a 30-megabyte drive with 512 cylinders and
8 heads. You must reconfigure for the type of external drive you are adding.
The BIOS parameter tables can recognize four types, as follows:
A: 512 cylinders, 8 heads, 30 megabytes (3,4)
B: 306 cylinders, 4 heads, 10 megabytes (4)
C: 306 cylinders, 6 heads, 15 megabytes (3)
D: 612 cylinders, 2 heads, 10 megabytes (no jumper on 3 OR 4)
The external hard drive you are connecting MUST be one of these four types.
The numbers in parentheses indicate which positions of the SW1 jumper block
must be jumpered to define it. Note that type D requires no jumpers. Configure
the board as noted for the external hard drive you are connecting.
The next step is to jumper the drive select position. This will be on the
hard drive itself. Between the controller cable cable and the data cable
connectors ON THE HARD DRIVE is a jumper block with 4 positions. Hold the hard
drive so that the PC board attached to it is on the bottom. With the controller
connector to your right, the jumper positions are numbered 1 through 4, left to
right. The external hard drive must be jumpered as 3, or the second rightmost
position.
Attach the cables to the external hard drive. Make sure you attach them so
that the cables go in the proper direction (usually in the direction of the pc
board attached to the drive). Now pass the cables into the 1000HD. If you have
only two boards the easiest way to do this is to move the memory board to the
farthest slot, leaving the middle slot empty, and pass the cables through the
opening in the back. If you have three boards attached, pass the cables above
the boards. In this case do not place them on top of each other or they will be
crushed when you close the case.
Attach the other end of the controller cable to the WX2 board. Attach the
data cable from the INTERNAL hard drive to the connector nearest the controller
cable on the board, and the data cable for the external hard drive to the
connector farthest from the controller cable. Carefully seat the controller
board back into the 100HD expansion slot nearest the fan. Now attach the 34-pin
card edge connector to the internal hard drive. Arrange the controller cable so
that it is not putting any strain on the internal hard drive connector (you
don't want this connector to pull loose without your knowing it, believe me!).
Apply power to the external hard drive and computer If the drive select
light on the external comes on immediately the cable is upside down at the
external drive. Turn off all power and reverse the cable. Apply power again.
Now allow the computer to boot. If you get a boot failure message, or if you
are asked to place a system disk in drive A:, then the connector to the
internal hard drive may be upside down. Check it.
If the internal hard drive boots properly your next step is to check drive
D:. Enter HSECT D: to hard-format drive D:. If you are successful, run FDISK.
Select option 5 ("Select next hard drive") and define the partition size.
REBOOT your system by pressing the red RESET button. This is very important
and must be done after running FDISK. Now enter HFORMAT D: to format drive D:.
If this format proceeds properly you are done.