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AM2: AMD Reinvents Itself

Automatically Overclocking SLI Memory

The memory module is clocked via the memory speed divider, which is in turn set by the CPU, normally to a maximum of DDR2 800 with an FSB of 200 MHz. With SLI memory technology, the FSB (Hypertransport, or HTT) is increased, which combined with the standard divider, results in a higher clock speed. In this case, the CPU multiplier is reduced so that it doesn't get overclocked.

Standard:

200 MHz * 14x = 2800 MHz / 7 = 400

Overclocking:

254 MHz * 11x = 2800 MHz / 6 = 466

The protective mechanism that adjusts the memory speed downwards to get a maximum of DDR2 800 is still activated.

At 2.8 GHz, which corresponds to the clock speed of the FX-62, the divider can assume the following values:

DDR2 800: dividers 6 and 7
DDR2 667: dividers 8 and 9
DDR2 533: dividers 10 and 11
DDR2 400: dividers 12 and 13

The processor thinks that it's working with an FSB of 200 and therefore adjusts the divider downwards. However, the FSB is actually increased to 254 MHz, which, in combination with the multiplier of 6, results in a memory clock of 466 MHz (DDR2 933).

With the multiplier set to 11, the memory divider is not optimal. Despite the high FSB, a memory clock of only 465 MHz can be attained.

With a memory clock of DDR2 800, the memory dividers 6 and 7 are available. Through the CPU's protective mechanism, the divider is set to 6.

2800 / 6x = 466 MHz (DDR2-932)

When SLI memory is activated, the HTT is set to 254, and the SLI technology automatically decreases the CPU multiplier to 11.

Through this, the memory clock can be increased to 465 - the value cannot be set manually.