Originally Posted by heero_yuy

I would hazard a guess that this is the higher 8 core spec processsor that the other four cores failed to perform in so is marked down in price. The dud cores are probably disabled by a bond wire option.

The other cores may well work but not be reliable at the clock rate of the working ones and if they're bonded out will not be accessable.

This is quite common, decades ago I remember the 2756 EPROM that was basically the working half of the 2716 EPROM but at a much lower price. IIRC there was a x86 CPU that had a dud co-processor so was marked as an SX type.

For the real old timers remember the undocumented orthogonal register set in the Z80 CPU?