You've got it. People think that just because Bloomfield posts big (30%) improvements over Yorkfield, that'll carry over to
all Nehalems. Nehalem variants differ more widely than Penryn variants.
Nehalem brings the biggest improvements in the MP server area and the smallest improvements in the desktop and notebook areas. And at least for the Extreme / DP server segments, clock speeds appear to be similar from Penryn » Nehalem.
MP Server: Beckton's improvements over Dunnington:
- 6 cores » 8 cores
- 6 threads » 16 threads
- 16 MB L3 cache » 24 MB L3 cache
- 2 channel RAM » 4 channel RAM
- 1067 MHz FSB » 4x QPI
- Core improvements
1.5 MB L2 cache/core » 512 KB L2 cache/core (downgrade)
Extreme / DP Server: Bloomfield/Gainestown's improvements over Yorkfield/Harpertown:
- 4 threads » 8 threads
- New L2 cache
- 2 channel RAM » 3 channel RAM
- 1333/1600 MHz FSB » 1x/2x QPI
- Core improvements
12 MB L2 cache » 8 MB L3 cache (downgrade)
Mainstream/Value: Improvements over Penryn:
- 2/4 threads » 4/8 threads
- New L2 cache
- Core improvements
- On-chip IGPU
1067/1333 MHz FSB » DMI (not an upgrade)
6 MB L2 cache » 4 MB L3 cache (downgrade)
I expect Penryn » Nehalem in the mainstream and value segments to be not unlike the Pentium M / Core » Core 2 transition.