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- Socket 939 mother board for 4 x 1GB Ram
January 11, 2007, 3:53 pm
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Re: Socket 939 mother board for 4 x 1GB Ram
g. bon wrote:
Your processor has the memory interface on it. Unlike an Intel processor
board, AMD has the memory controller right inside the processor. If the
processor cannot be coaxed to drive the four sticks, it can be because
of an artificial restriction in the BIOS, or it can be a limit of the
processor's memory controller itself. (The AMD documentation,
specifically mentions slowing the clock when four sticks are present,
so the BIOS writers do that for "defaults". Then a user has to fiddle
with it manually, to get further than that.)
To run four sticks, you set "Command Rate" to 2T. The BIOS should have a
setting for that. Just like on Nforce2, the 2T option allows the
address/command bus to settle for two clock cycles, which allows higher
clock rates to be used. The two cycle presentation of command/address,
reduces performance (because only half the number of commands or
addresses can be sent across the bus), but it does allow a higher clock.
If it is a DFI board, it should offer you plenty of stuff to play with.
You can use the bandwidth display field on the memtest86+ test screen,
to monitor how well your memory adjustments are going. You can, for
example, run memtest86+ with the system default memory settings, then
tweak the settings (2T, plus bump the clock) and run memtest86+ again.
The memory bandwidth display will tell you whether what you are doing
is helping a lot or not. Like whether you are winning the battle...
A tiny bump in Vdimm, if the setting is available, can help. I expect
you were already doing that, when testing at DDR540.
Also, you've tested your old sticks at DDR540. Do the two new sticks
by themselves, also run at DDR540 ? There could be some difference
in the overclock range of the two pairs. But bus loading is what
causes the dramatic shift in max clock, when four DIMMs are present.
Articles like this one, show how aggressively the settings can be
with two sticks or four sticks. On this page, they run four
sticks at 200MHz, with command rate 2T. These memory tests, are
not an attempt to "overclock to the max" on memory, but are intended
to show what is needed for stock speeds. Each board responds in the
same way, because the processor is what sets the limit.
You should also test with Prime95 (mersenne.org) after you are
finished, as it is a more sensitive test that your system is
stable at 100% load.
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