HP-75 RAM expansion?

[Paul Berger (Canada)]

The only memory upgrade that I can think of that would be that simple would be adding the equivalent to the 8K module, but even that would not be that straight forward. The MAR chip in the 75 that is the interface to the RAM is set up for using 2K chips, so it provides 4 chip select lines to the connector for the 8K module. If the upgrade was done using 2 chips that would suggest they are 4Kx8 and addition logic would be required to encode the 4 select lines into 2 4K select lines and the extra address bit on the 4K chip.