Q: Can I attach a hard disk to my Rainbow?
Yes, the Rainbow can have a hard disk. In order to connect one, you must have a hard disk controller. Two hard disk contollers were made for the Rainbow 100: Digital's own controller and the Micro/CHS Dual Hard Disk controller. Digital's own controller supports one MFM hard disk up to 80 MegaBytes in size. It connects only to MFM drives using the ST-506 interface. The Micro/CHS controller supports two MFM hard disks. The Micro/CHS controller is extremely rare. The hard drive controller is attached at the front right of the motherboard and uses two front-most expansion ports.
The problem with Digital's controller is that it uses a proprietary cable to attach to the hard disk. The ST-506 interface uses two card-edge connectors and usually makes use of two separate cables. The Rainbow uses only one cable which splits into the two connectors.
The following letter written by an unknown source describes how to build your own cable and the problems surrounding Digital's cable:
I followed the schematics for making a new cable and compared
with the original one. All connections were the same, *but* on
the original cable two lines had quite a remarkable resistance
(pin 10 and 12 on the big disk-connector). The two lines are
signals from the disk called 'track 00' and 'write fault'. No
wonder it didn't work properly !!So, I made myself a new cable and installed a ST-225 disk. I
installed MS-DOS, CCP/M-86, Windows, lots of utility programs
and some games. No problems that far... Using the disk for
a couple of days, convinced me it worked properly.Therefore I installed a 40Mb NEC D3142 disk (3.5", 615 cyl,
8 head) and uploaded almost every program I have on three
partitions with MS-DOS 3.10b, CCP/M-86 and CP/M-80. The
'wutil 3.2' program did not report any bad sectors, nor did
the 'Norton Disk Test'.Right now I have used the current setup for about a week,
without any troubles what so ever.Here's the schematics:
r = Red mark on flat ribbon cable.
M = Mark on the connectors (for pin nr 1).
o = PIN which is used.
/ = PIN not used, do NOT cut the cable line, it's the pin on the
connector which is not used...Cut between as shown________________________________________
| | | |
V V V V
1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 FLAT
1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 RIBBON
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |_______
o o o o o o o o o o o o o o | | o o o o o o o o o o | | |________ \
| | | | | | | | | | | | | | | | | | | | | | | | | | | |_________ \ \
r | | | | | | | | | | | | | | | | | | | | | | | | | |__________ \ \ to 20
| | | | | | | | | | | | | | | | | | | | | | | | | | \ \ pin card
r | | | | | | | | | | | | | | | | | | | | | | | | | \ edge
| | | | | | | | | | | | | | | | | | | | | | | | | | connector
r | | | | | | | | | | | | | | |_|_|_|_|_|_|_|_|_|_|________________
| | | | | | | | | | | | | | |___|_|_|_|_|_|_|_|_|_|______________ |
r | | | | | | | | | | | | | | | | | | | | | | | | |
| | | | | | | | | | 1 | 1 | 1 | 1 | 2 | 2 | 2 | 3 4
_1_|_3_|_5_|_7_|_9_|_1_|_3_|_____7_|_9_|_1_|_3_|_5_|_____________3_4_
|M |
| 34 PIN CARD EDGE CONNECTOR |
---------------------------------------------------------------------The 20 pin card edge connector:
2 2 2 3 Cable line
7 8 9 0 numbers
| | | |
| | | |
1 1 | 1 1 | 1 2
___2___4___6___8___0___2_|_4___6_|_8___0_
|M | o | o |
| o o |
-----------------------------------------
1 1 1 1 1
1 3 5 7 9 1 3 5 7 9Finally the 34 pin connector for the controller card, just
make sure the mark on the cable is lined up with the nr 1
pin on the connector.