Here's one explanation I found on the Hocp forum:
thanks to *foo
Quote:
On the P4 platform, the host clocks (CPU clocks) are different from earlier Intel platforms. Instead of acting as a voltage source with a set voltage swing, it acts as a current source and injects a set amount of current into the transmission line. You have to use parallel termination on the line to set the voltage swing.
The "differential current" option in the Abit bios just lets you fiddle with the amount of current injected into the line (by mulitiplying some set value, which they don't tell you). This effectively lets you change the voltage swing of the clocks.
The Abit TH7-II manual says "This option allows you to select the current multiple of CPU clock. The options are: 4x, 6x, 5x, 7x. The default setting is 6x." (Bad English theirs).
They call it "differential current" because the clocks are differential. That means instead of a single clock, you have a CLK and CLK#. One is going high while one is going low (for those who care, they operate in odd-mode differential signalling). That means when CLK is on, CLK# is off. Thus, differential current.
