Ai Overclock Tuner - Manual vs XMP

New to OC'ing - Just curious what would changing the AI Overclock tuner from manual to XMP do? Does it just auto set mem settings? Would it allow the use of lower volt's? (i.e. are there any advantages for oc'ing). I currently just typed in the bios settings - 8,8,8,20.

Thanks,

Current Setup - i7-930, Asus P6X58D prem, kingston hyperx dd3 1600 (xmp ready), radeon hd 5850, noctua nh-u12p se2

Ai Overclock Tuner.....................[Manual]
CPU Ratio Setting......................[19.0]
Intel(r) SpeedStep(tm) Tech............[Disabled]
Xtreme Phase Full Power Mode...........[Enabled]
BCLK Frequency.........................[200]
PCIE Frequency.........................[100]
DRAM Frequency.........................[DDR3-1603MHz]
UCLK Frequency.........................[3208MHz]
QPI Link Data Rate.....................[Auto]

CPU Voltage Control....................[Manual]
CPU Voltage............................[1.17500]
CPU PLL Voltage........................[1.80]
QPI/DRAM Core Voltage..................[1.20000]
IOH Voltage............................[1.14]
IOH PCIE Voltage.......................[1.50]
ICH Voltage............................[1.20]
ICH PCIE Voltage.......................[1.50]
DRAM Bus Voltage.......................[1.64]
DRAM DATA REF Voltage on CHA...........[Auto]
DRAM CTRL REF Voltage on CHA...........[Auto]
DRAM DATA REF Voltage on CHB...........[Auto]
DRAM CTRL REF Voltage on CHB...........[Auto]
DRAM DATA REF Voltage on CHC...........[Auto]
DRAM CTRL REF Voltage on CHC...........[Auto]

Load-Line Calibration..................[Enabled]
CPU Differential Amplitude.............[800mV]
CPU Clock Skew.........................[Delay 300ps]
CPU Spread Spectrum....................[Disabled]
IOH Clock Skew.........................[Auto]
PCIE Spread Spectrum...................[Disabled]

C1E Support............................[Enabled]
Hardware Prefetcher....................[Enabled]
Adjacent Cache Line Prefetch...........[Enabled]
Intel(r) Virtualization Tech...........[Disabled]
CPU TM Function........................[Enabled]
Execute Disable Bit....................[Enabled]
Intel(r) HT Technology.................[Enabled]
Active Processor Cores.................[All]
A20M...................................[Disabled]
Intel(r) SpeedStep(tm) Tech............[Disabled]
Intel(r) C-STATE Tech..................[Disabled]

Realtemp - Cores0-3 = 69,68,65,62

Leave Ai Overclock Tuner set to Manual, otherwise the BIOS changes the DRAM frequency and timings, and increases the corresponding voltages so that the resulting settings correspond to the ones recorded in one of the two memory SPD profiles.

I would also disable c1e support.