From the P35 datasheet (31696602.pdf page 352):
http://www.intel.com/design/chipsets/datashts/316966.htm
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The system memory controller supports three memory organization
modes, Single Channel, Dual Channel Symmetric, and Dual Channel
Asymmetric.
Single Channel Mode
In this mode, all memory cycles are directed to a single channel.
Single channel mode is used when either Channel A or Channel B DIMMs
are populated in any order, but not both.
Dual Channel Symmetric Mode
This mode provides maximum performance on real applications.
Addresses are pingponged between the channels after each cache line
(64 byte boundary). If there are two requests, and the second request is
to an address on the opposite
channel from the first, that request can be sent before data from the
first
request has returned. If two consecutive cache lines are requested,
both may be retrieved simultaneously, since they are ensured to be on
opposite channels.
Dual channel symmetric mode is used when both Channel A and Channel B
DIMMs are populated in any order with the total amount of memory in
each channel being the same, but the DRAM device technology and width may
vary from one
channel to the other.
Dual Channel Asymmetric Mode with Intel Flex Memory Mode Enabled
This mode trades performance for system design flexibility. Unlike
the previous mode, addresses start in channel 0 and stay there until
the end of the highest rank in channel 0, and then addresses continue
from the bottom of channel 1 to the top. Normal applications are unlikely
to make requests that alternate
between addresses that are on opposite channels with this memory
organization; so, in most cases, bandwidth will be limited to that of
a single channel.
Dual channel asymmetric mode is used when both Channel A and Channel
B DIMMs are populated in any order with the total amount of memory in each
channel being different.
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That doesn't sound like an exact match for your manual's description.
That still sounds like an "A1 + A2 = B1 + B2 for dual channel" type
chipset.
If you want to test it on your board, there is a way to do that. I
modified memtest86+, to test an nforce2 config consisting of 3x512MB,
and you could do the same for your P35, if you have an odd assortment of
memory.
The code I added is specific to the amount of RAM, so the code has to be
modified for the test configuration. (I didn't waste time adding code to
automate
the setup.)
http://groups.google.ca/group/alt.comp.periphs.mainboard.asus/browse_frm/thread/27e23db56f02cbf2
Paul