Yes. As was noted by Wes, the bus speed can drop when you go to 3
sticks. This drop is related to the fact the the 754 package only
provides 6 clock pairs, with each DIMM requiring 3 clock pairs. When
you put in the third DIMM an external clock buffer is recommended and
while DIMM1 gets its own address and command pins, DIMM2 and 3 must
share the second one.
Also, the use of Pstate transistions (basically Cool'nQuiet) can result
in unpredictable results when 3 DIMMs are used.
On the K8NE, the owners manual, specifies that the max speed for a
single DIMM is DDR400. For 2 DIMMs it is DDR400 as long DIMM1 is filled.
For 3 DIMMs, it is DDR333 if all single sided DIMMS or the combination
of Double/Single/Double are used and DDR200 for any other combination.
(note: this is double sided, not dual channel).
Lastly, there is an approved list of DIMMs that can be used.
See page 2-12 in
http://www.asus.com.tw/pub/ASUS/mb/sock754/K8N-E_DX/e1883_k8n-e_deluxe.pdf
There is supposed to be an updated list on the ASUS site, but I haven't
found it.
