-*- text -*-
This is a list of possible replacement parts for OSI board repairs.
History:
11/18/2011: updated part numbers on molex connectors, clarified some
notes on buffers.

Replacements for OSI Molex PCB connectors:

12-pin right-angle (horizontal) edge connector (sockets): Molex 09-52-3121
12-pin vertical molex connector (sockets): Molex 09-52-3123
12-pin header (pins): Molex 26-60-2120

Notes on PIA:
6820 PIA can be hard to find. The 6821 and 6521 are electrically improved
direct replacements


Potential replacements for 8T26/8T28:

1) note that the 8T28 and 8T26 are basically interchangeable in OSI
   computers, as long as a machine has uniformly one or the other.
   For RAM boards, it doesn't matter which you use: you can use either
   chip, or you can use an 8T26 in one socket and an 8T28 in the
   other.

2) 74LS243 or 74HC243, 14-pin quad bidirectional transciever.  This
   can be used in many OSI boards, since on many boards, the input
   and output buffers on the 8T28 are tied together.  Like 8T28,
   these have complementary read/write enables.  Differs from 8T28
   in that there are no separate inputs/outputs; just A1-4 and B1-4.
   The i/o pins are tied together on most OSI boards, except the
   542 keyboard.  Where it can be used, an adapter would have
   to be made.

3) Nat. Semi DS8641 (formerly Dallas Semi. part).  Similar to 8T26,
   except pinout is different.  Open collector outputs require
   resistor termination.  Also apparently obsolete, so not a great
   choice.