Remember, when nothing else works, as a last resort - RTFM!!.
P4T manual, pages 22 & 23 (amended from 128Mb to 256Mb):
1. The memory configuration of channel A (RIMMA1 and RIMMA2) and channel B (RIMMB1 and RIMMB2) must be identical, (see below).
2. C-RIMMS (Continuity RIMM) must be used to complete the sockets that are not populated by RDRAMs. A C-RIMM is necessary to avoid breaking the signal lines, which make serial connection in a Rambus interface, such as used in this motherboard. This ensures the electrical integrity of a Rambus interface.
3. When C-RIMM are required, it is recommended that they be inserted into RIMMA2 and RIMMB2.
Total system memory is 2Gb max.
Examples. (Note: When using only two memory modules, it is recommended use use configuration (a).)
(a).
RIMMB1--------256Mb RDRAM
RIMMB2--------C-RIMM
RIMMA1--------256Mb RDRAM
RIMMA2--------C-RIMM
(b).
RIMMB1--------C-RIMM
RIMMB2--------256Mb RDRAM
RIMMA1--------C-RIMM
RIMMA2-------- 256Mb RDRAM
(c).
RIMMB1--------256Mb RDRAM
RIMMB2--------256Mb RDRAM
RIMMA1--------256Mb RDRAM
RIMMA2--------256Mb RDRAM
Working on the above, what you have, and what you're buying, you should install as follows:
(c).
RIMMB1--------256Mb RDRAM
RIMMB2--------64Mb RDRAM
RIMMA1--------256Mb RDRAM
RIMMA2--------64Mb RDRAM
