Maz 8MB, 1MB or 2MB simms only. Depends on processor speed: 16 used 85ns 20 ones used 80ns. 2 slots, one of them is 32bit slot that allows u to put a memory card in there to go over 16mb. There were bunch of ECA's on those P70's, check the computercraft.com about it and check that ECA's that is done on your P70. I found that my model 35 bios was not dealt with except one other ECA slot riser was dealt with. Interesting. Far easier done by replacing that notorious slow MCA hd with scsi controller and a scsi hd under 1023MB limit. That gives easier way to deal with when needs to replace that hd instead of searching out another remaining MCA hd. MCA hds is not made anymore but scsi is. Can use TI or Cyrix 486DLC or DLC2 with coprocessor set in place of stock cpu. These are very effective cpus. Every time anyone wants to talk about ibm anything please state the model and suffix. Thanks! Keep PS/2ing! Wizard