Working on the x5670 a little more. Max I can hit stable with 1.328 vtt and 1.28v core is 4200mhz loaded. The bloodrage can force the turbo multi of 24x when all cores are loaded. I'll try and up the vcore to over 1.3 and see what happens.
Memory Timings
tCL (CAS Latency) .................: 7T
tRCG (RAS to CAS Delay) ...........: 7T
tRP (RAS Precharge) ...............: 7T
tRAS (Precharge Delay) ............: 21T
CR (Command Rate) .................: 1T
All Voltage Settings
CPU Core Voltage ..................: +80mV hwinfo reports 1.28 with all cores loaded
CPU Vdroop Compensation ...........: disabled
CPU VTT (UnCore) Voltage ..........: +140mV 1.328v
Memory Voltages
DRAM Voltage ......................: 1.72V
Chipset Voltages
X58 IOH Core Voltage .............: 1.24V
X58 IOH VCCA 1.1V ................: 1.134V
X58 IOH VCCA 1.5V ................: 1.530V
CPU Bclock (FSB) ................: 175MHz
QPI Link Fast Mode ..............: Enabled
QPI Multiplier ..................: x18
QPI Target Speed ................: 3158MHz
CPU Core Multiplier .............: x22
CPU Core Target Speed ...........: 3820MHz
CPU Uncore Multiplier ...........: x20
CPU Uncore Target Speed .........: 3509MHz
Memory Bus Multiplier ...........: x10
Memory Bus Target Speed .........: 1750MHZ
PCI Express Bus Clock............: 102MHz
A few things to try here, may help, may not.
CPU Core Voltage ..................: +80mV hwinfo reports 1.28 with all cores loaded
Try this at ~+100-140 Whatever value it takes with VDroop enabled to arrive at ~1.35 under load.
CPU Vdroop Compensation ...........: disabled
Enable this
CPU VTT (UnCore) Voltage ..........: +140mV 1.328v
I never really had to run this quite so high, but it may be due to your 1750MHz ram frequency.
CPU Uncore Multiplier ...........: x20
CPU Uncore Target Speed .........: 3509MHz
Memory Bus Multiplier ...........: x10
Memory Bus Target Speed .........: 1750MHZ
PCI Express Bus Clock............: 102MHz
You could try dropping your memory multiplier to x8, would probably allow you to drop your VTT (and memory voltage back to 1.65) and may reduce stress on the IMC. This would also allow you to drop the uncore multiplier to x16, though your uncore is probably not an issue at 3509 anyway, so if it works out you could remain at x20 if you wish. There was testing done back in X58's heyday that showed virtually no gain for memory frequencies above 1600MHz, now this was done on the four core cpus, so if you notice a decrease in performance benchmarks obviously feel free to try increasing again. Note that for the time being though we're just trying to get your CPU frequency higher, that's going to trump any increases the memory would give you no matter what. As for the pci express clock, I've never seen any benefit to changing this from the default 100MHz except at extremely high BCLK (212-220). Once you can find your max stable clocks, then you can just drop it back to whatever you feel comfortable with for mining.