David,
The solution to run code from RAM is as follows:
Software: You must inform the compiler where your code which you intend to be in RAM will start.For example if your RAM starts from 2000h ,compile your code so it will reside in 2000h up.
After compilation you can store the code in EEPROM and copy it from EEPROM to RAM at Reset , then jump to 2000h.
Hardware: PSEN ored with RD as was said
Yossi