The same XtremeSystems site owner who reported that the Mac mini could be processor upgraded simply by swapping out the socketed Intel processor, now reports that the unreleased Merom 64-bit mobile processor is also similarly compatible:
It is possible to drop in Merom into Mini, one hell of an upgrade path. confirming this is a working combo, just drop the chip in.
Further details are limited, presumably due to non-disclosure agreements for pre-release hardware. Intel's Merom processor is a mobile 64-bit processor due in late 2006.
The Merom is said to offer 20% more performance than the current Core Duo at the same battery life. The Merom will reportedly come with 4MB L2 Cache (up from 2MB on Yonah). This backward compatible capability has been advertised by Intel:
During a separate briefing, Intel's Mooly Eden showed a benchmark pitting a Dell Core Duo system against the same system with a Merom processor (Eden literally swapped out the Core Duo CPU and stuck in a Merom processor, partly to showcase its backwards comptability). The benchmark was a custom Quake 4 timedemo, with the Core Duo system scoring 106.6 fps while the Merom system scored 134 fps: advantage Merom by just over 25%. We don't know any of the specifics of the settings on the systems, other than they were claimed to be identical.
While the Intel iMac also has a socketed CPU, the MacBook Pro CPU is soldered to the motherboard.