Currently working on an X58 motherboard round-up and yesterday I had the time to test the overclockability of the rampage 2 extreme.
I didn't go for the excessive voltage results as I'm still on stock air cooling (awaiting mounting bracket from Noctua).
BCLK:
221MHz is no problem, even on stock voltages. Haven't been able to surpass the 222MHz barrier, which seems to be a chipset/motherboard related problem. Officially, manufacturers tell users that going beyond 222MHz bclk is a nogo, as the chipset is somehow limited to that frequency. Recently, more and more motherboards pop up, though, that give you the chance to break the limit and hit 230-235MHz!
MEMORY FREQUENCY:
Of course, overclocking the memory is limited to the memory chips, as the maximum frequency varies from kit to kit. However, certain motherboards can make your memory overclock just a tad higher.
Stock voltages:
668MHz CL7
651MHz CL9
Ironically, CL9 clocks much worse
Elevated voltages (1.45/1.85v):
850MHz CL7
1001MHz CL9
Note: when I did the same tests on the Intel DX58SO motherboard, I only achieved:
980MHz CL9
Althought the benchmarks (and thus request for stability) is different, I can tell you that even with 1.95v, I could not run 1M above 1GHz CL9.
Kudos for the R2E, in other words
CPU FREQUENCY
Using stock voltages (1.15v/1.8v pll) I found no difference between HT-on and HT-off overclocking:
Using a slightly higher voltage (1.2v/1.89v pll), there was a difference of 75Mhz between enabling and disabling HT.
To be honest, I'm quite impressed by this cpu: I'm closing in on 4GHz on stock air cooling using only 1.224v. TO BE CONTINUED
OTHER RESULTS
Fastest 4M run using stock voltages:
Fastest 4M run using elevated voltages:
Fastest 1M using elevated voltages:
995MHz 3Dmark06 stable:
When the Noctua mounting bracket arrives, I'll continue with more extensive testing.