Hi More back on subject, the MRAM looks like it is a non-distructive read, unlike the core. Back on cores: It seems like they also used a 1/2 opposite inhibit while doing reads to give them a little more noise margine. This way, cores without a x or y would have a 1/2 wrong way and those with only x or y driven would have 1/2 positve. The matching would get 2 - 1/2 or a full 1.5 write. Both X and Y would be driven with the average Im, of all of the cores, and not half. Dwight