DIMM Memory Board

    This is the DIMM board the came as an option on the ALR 6x6.  Increasing the capacity from the 2 GIG of RAM that the SIMM board could handle, to a whopping 4 GIG!  To quote from the ALR web docs:

    "The optional DIMM memory board has 16 DIMM sockets for system memory. These 16 sockets are organized as four banks of four sockets. All sockets in each bank on the memory board must be filled with the same type and speed DIMMs (60ns or faster). Always use 3.3 Volt, buffered (even RAS) 168-pin, Fast Page Mode DIMMs with a 4K refresh, ECC (Error Checking and Correcting) capability, and a maximum height of 1.6 inches. Up to 4-GB of RAM may be installed on the board."

    The memory controller on the board is part of the GX, or Orion, chipset.  This chipset used memory interleaving to increase the throughput to the CPUs.  The result:  memory must be installed in sets of 4, but the motherboard is able to access 4 different DIMMs at once!

    Now for the issues we faced.   First, the memory, being buffered, ECC, non-EDO, and DIMMS, is quite hard to get ahold of, and is about a quarter to half as much more expensive then it's more standard counterparts.  This RAM was only popular in servers (anything with over 4 memory slots).  (There is an EBAY auction that states that EDO DIMMS work.  Anyone out there that can confirm this?)

    Secondly, some of the boards out there seemed to have defects from the factory.  In the above picture, you can see a "NB" on the DIMM slot.  This stands for NonBuffered, and is the wrong slot for this board.  We have some SIMM boards on the way so that we can continue testing.  But, because we had a board that SDRAM could fit into, we tried an experiment with some extra PC100 DIMMs we had lying around.  For the record, the board hated it, although no damage was done.

   According to Ken Stoen, cutting the offending pin out of the slot caused the buffered DIMMS to work fine in the defective boards.  Looks like just a wrong box of parts was dumped into the mix...