jakethompson1 wrote on 2023-11-17, 01:03:
Any thoughts why this board vendor populated the jumpers to hardwire the board for 256K, double bank cache, but didn't put those chips on there?
I have seen some boards where they omitted chips and replaced them with eight diagonal resistors; could the board vendor have done that instead or is the need to be able to tri-state those outputs inherent in the design?
This is just guesswork, but you asked for "any thoughts": The vendor shipped the board in the 256K an 0K configuration, and they only omitted components in the "0K" edition that had a significant cost in the BOM. Jumper wires might be expensive to install, but they are very cheap to buy, so the vendor didn't think about removing them when they specified the 0K edition.
The '244 is a unidirectional buffer, and at that location on the board, I am very confident that it is used a address buffer, input is the processor address bus, and output is the cache address pins. As the cache chips are the only thing on the output side, and the 0K edition doesn't have the cache chips installed, the tristate option is definitely not required. As long as loading of the address bus is not an issue, the '244 chips can be replaced by 8 jumper wires each.