Odd glitch in a PDP-8/i

Ok, here is one for the true wireheads among us. I finally got some time to start working on the PDP-8/i in my collection, and started keying in some test programs with the intent of getting the timing on the TTY interface tweaked in so I could load some serious software, and found that the old beast seems to have an odd problem. See if anyone has hit on this one and has a suggestion... I can't seem to write into location 0 on any memory field?!? Regardless of what I write into the location, it always reads back as 0000. I can write into any other location, and all of the primary logic functions seem to be ok... (I can load/run programs as long as they don't need location 0) The 'write all zeros' test program (that org's at location 4) runs as expected... Thots, suggestions, comments, eek!?! -jim --- jimw(a)computergarage.org The Computer Garage - http://www.computergarage.org Computer Garage Fax - (503) 646-0174