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BIOS And Overclocking

X48 Motherboard Comparison
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BIOS Frequency and Voltage settings (for overclocking)
FSB Frequency 100 - 700 MHz (1 MHz)
Clock Multiplier Adjustment Yes
DRAM Frequency FSB x 1.0, 1.2, 1.25, 1.33, 1.5, 1.6, 1.66, 2.0
PCIe Clock 90 - 150 MHz (1 MHz)
CPU Vcore 0.50000- 1.6000 - 2.35 Volts (0.00625/0.05 Volts)
CPU FSB Voltage 1.20 - 1.55 Volts (0.05 Volts)
Northbridge (MCH) 1.25 - 1.625 Volts (0.15 Volts)
Southbridge (ICH) None
DRAM Voltage 1.80 - 3.35 Volts (0.05 Volts)
CAS Latency Range
tCAS: 4-11; tRCD: 1-15; tRP: 1-15; tRAS: 1-63

Carried over with few (if any) changes from the previous X38-DQ6, the X48-DQ6 BIOS provides broad voltage and frequency ranges to meet the demanding needs of most overclockers.

The CPU Front Side Bus clock rate ranges from 100 to 700 MHz, well beyond the capabilities of the chipset. Even with extreme cooling and voltage modifications, top overclockers rarely exceed 600 MHz FSB on any motherboard.

Memory ratios are listed as DDR2 data rate to FSB clock rate, so each setting appears twice as high as the actual multiplier. All ratios are available at all bus speeds, but a handy chart on the side appears when selecting a data rate, to tell builders which northbridge bootstrap applies. Choosing the "wrong" bootstrap can cause the system to become unbootable at otherwise achievable frequencies, but using the chart to find the correct ratios can prevent these issues.

The CPU core voltage is available from 0.500 to 1.600 volts in ultra-fine 6.25 millivolt steps, while processors that require even more voltage can only be adjusted in 50 millivolt steps. The higher voltage levels generally apply only when overclocking older Pentium D processors, though we have seen a few "extreme overclockers" with equally extreme cooling configurations use insane voltage levels on Core 2 processors.

DRAM voltage ranges up to 3.05 V in 50 mV steps, but even the most avid overclocker probably won't need more than 2.60 V for excessively-cooled DDR2.

While CPU core voltage is listed in actual values, the remaining voltages are labeled as "over stock" levels. Determining the actual voltage chosen requires one to know what the stock voltage was supposed to have been.

We chose 1.60 volts core and the +0.30 volt FSB setting, reaching 4023 MHz on our Core 2 Duo E6850. Lowering the CPU core multiplier to 6x allowed us to reach an FSB limit of 538 MHz.

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