In the last week I got a couple more CPUs to play with and also repaired the motherboard.

The first CPU is an E6850, decent clocker too bad for the low FSB wall (~ 550 MHz single stage cooled, ~ 520 MHz when air cooled).
Managed to run 32M at 4770 MHz with a very good efficiency.

E6850 530x9
Cellshock PC8000 4-4-4-4 636 MHz trfc 26 PL 7 - VDIMM 2.9 volt just to be safe, 2.7 or 2.8 volt should be enough



http://hwbot.org/submission/2585225_

The second CPU is a Xeon E3110, still have to try it on cold (not the best days to fireup a single stage, 30?+ C in Milan today) but looks good at least FSB wall wise.
Managed to boot with both motherboard and CPU air cooled at 650 MHz of FSB.

E3110 650x6
Cellshock PC8000 650MHz 4-4-4-4 trfc 26 PL 10 - VDIMM 2.9 volt just to be safe



http://valid.canardpc.com/1cxjxy

The trick to run this particular Cellshock kit at such high frequency/low latency combination and FSB : DRAM ratio 1:1 is play with drive strengths, in this case I used +3 on all settings in the drive strength's page.
Drive strengths on auto -> no more than 585 MHz in 1:1
1333 MHz OC profile -> boot up to 610 MHz in 1:1
+3 on everything -> boot up to 650 MHz 1:1
PL9 could be possible, I'll work on it in the next days.