On Jan 24, 2012, at 3:09 AM, Pete Turnbull wrote:
  David Riley wrote:
  I'll vouch for that.  My backplane (I
don't currently have a box) is
 an H9273; the designers kindly left proper square wire-wrap posts
 coming out the back.  Updating to 22-bit was a very simple operation
 with a manual wire-wrap tool, and everything appears to work
 perfectly.  If you do that, make sure you run your wires in the same
 serpentine pattern as the bus!  
 Are you sure yours was an H9273?  Not H9270?  I've never seen an H9273 with wirewrap
pins, and H9273 is straight (Q18-CD), not serpentine. 
Ah, yes, that's what I mean.  Momentary memory lapse, aided by the fact that it's
not marked on the thing anywhere I can see.  Four slots, right?
- Dave