<On the MPU-A: <Pin 68 has no connection, right at the card edge. <Pin 77 goes to an 8T97 pin 9 (an output pin). < <Now that I look at it this way, this is VERY WEIRD! <Maybe very bad? Does this mean that the CPU can not <write to this memory card? Does the front panel <arbitrate pin 68 for the CPU? Arbitrate is the wrong word. PWR/ is generated by the CPU as is SOUT, those combine in the front pannel to make MWRITE. Mwrite is used to deposit front pannel data in ram and the cpu data to ram. Most memories use Mwrite to write data but some will use PWR/ and SOUT instead (for non frontpannel systems). I belive the ram you are using wants Mwrite. So you need to see if there is activity on the mwrite line (68) If it's there when you hit deposit then look at sout and PWR/ on the bus. Do you have prints for the cpu and FP? they are a must as you can literally follow the signal forward or backward to the problem. Or if you have BURSKY, Hayden books THE S100 BUS HANDBOOK that will do as it has the IMSAI prints in it. Allison