Yes, I am absolutely going to do this. Thanks! I'll let you know how it goes.When you have finished testing your RAM, you could make the ROM from my article and run the programs from it (you won't need the hardware adapter now BASIC is running). Two of those programs work by writing the whole memory with a checkerboard pattern. First (one of them) fills the whole memory from 0400h to 7FFFh with byte 00. Then after that it writes over alternate address locations with FF. (the other program does the reverse FF then 00). The idea behind this is to check that writing into memory cells doesn't alter byte values at other locations. Also, because there is a delay in inspecting that programmed pattern (done with the M/L monitor) it also helps confirm that the memory retention is good and that the DRAM IC's all have a normal refresh function , as this is another way that DRAM IC's can fail, aside from the other 4 ways their outputs can be defective.