I purchased a complete boardset from an R3000 predator in Europe because it was too expensive to ship the whole rack to Australia. This boardset had an IO3B. Great! I can immediately swap in a Crimson IP17 board (in place of the R3000s/MC2s) and make this machine a 4D/510 Crimson - or so I thought. When this IO3B and IP17 combination was booted, the diagnostics failed and the machine dropped into POD (I'll get the exact details of the error and diags produced later). Hmmm. Better make sure all the boards are seated correctly and that the cables are connected. Do this, boot it again, same problem! At this stage I gave up and put the R3000s back into the machine thinking that perhaps this IO3B is a bit flakey.

The answer came along several months later from an anonymous source. Apparently there is a jumper on the IO3B board (030-0222 but could also be on 030-0180 and 030-0210) near location C0F0 (I'll photograph it soon) that must be set on either:

• pins closest to the backplane connectors for IP17 R4000/R4400 Crimson/PowerSeries
  
  
• middle pins for IP7 & IP15 R3000 PowerSeries

The anonymous source also mentioned that it was important that the IO3/IO3B have version 010 PROMs.