you should match it by

• Speed
• Size
• architecture

• A pair of matched memory modules installed in connectors DIMM1 and DIMM2 and another matched pair installed in connectors DIMM3 and DIMM4

  **********************************************
  Inspiron XPS Gen2
  
  Custom Built System
  AMD Athlon FX55
  A8N-SLI Premium
  2x 1GB Dual Channel DDR
  Chieftec Bravo Case BX-01SL-SL-SL
  Dual 350 Watts Thermaltake Fan Less PSU
  Nvidia 6800 GT
  146 GB Ultra 320 SCSI Seagate Cheetah 15K
  Adaptec Scsi Controller
  Liquid Cooled System

   

  Message Edited by cmisidro on 08-22-2005 11:05 PM

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@dillfest wrote:
I had 4 sticks of 128 Mb PC3200 RAM in my Dimension 4600. Today I removed 2 sticks and added 2 512 Mb sticks of PC3200. On rebooting, it recognized the memory, but I'm now only running in single-channel mode instead of dual-channel. I thought as long as the pairs were identical, I would stay in dual-channel. Can anyone shed some light on this?

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Most likely you didn't realize that the pairs are NOT next to each other.  The slots are numbered 1,3,2,4.  Notice the colors - 2 white, 2 black.  Put the new sticks in a matching set of slots.

Also, then boot to bios and make sure that you're running at 400mhz.  If you bought CL 2.5 memory you won't be.