Precision Workstation 690 memory installation

Question

At work, I have a Precision 690 that came with 4GB of RAM total, 1GB chip in each riser.  I ordered 2 more gigs (two 1GB chips) because it must be installed in pairs.  However, after installing, I receive an error message every bootup of a memory mismatch.  Is there a certain order installation I need to follow, or, is it because it's quad processor workstation, and I actually have to add RAM in quads and not pairs?  Or is it something else?

ejn63 · Answer

Yes, that is what Dell recommends: ' This version of the Dell Precision 690 is equipped with a 1000 watt power supply and memory riser cards which plug into the motherboard. The memory riser cards double the number of DIMM slots from 8 to 16 and all memory is installed on the risers. Since the 690 has a quad memory bus architecture, Dell recommends that all four memory channels be populated with DIMMs for maximum performance.'

anonim · Answer

Is this valid only for quad processor? My 690 came from Dell with 2x1GB memory and I added later another 2x1GB. I still have bank 1 free (4 risers). When I want to add some more memory, is it necessary to fill up all other 4 risers?

useriffic · Answer

Thanks for the input guys.  we went ahead and ordered two more chips.  It would seem as if you could run it with the two chips, but you just can't use it.  The dell utility gives some strange readings on the two extra chips,  like different memory access times.

tphillips63 · Answer

This chipset (intel 5000) basically is a 4 channel (4 DIMM) ssytem so to get maximum memory performance you do need a minimum of four DIMMs filled. With two you memory bandwidth is actually less than half of what it could be.

anonim · Answer

If this is the case, why Dell sells 690 with 2x1GB instead of 4x512MB?

useriffic · Answer

That I cannot explain. All that I know is that when I attempted to install 2 1GB memory modules, I received an error message at every boot up.  When I tried a different configuration, the workstation wouldn't even boot past the BIOS; at least in the first configuration, I could boot to windows.  Perhaps if you're mixing bus speeds on the chips, it needs to be installed in quads so that all of the DDR2 RAM modules will run at the speed of the slowest module in a quad processor application.

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