KalieMa Posted January 21, 2007 Share Posted January 21, 2007 Hi, I just recently built a system with an Asus P5N-E SLI mobo which features the new 650i chipset from nVidia. To accompany it, I picked up the XMS2 6400C4 RAM due to it's "SLI Compatability". Unfortunately, it's simply not working out as planned. With the Asus board, I can run at the advertised 4-4-4-12 but only at 2T. The EPP settings and the board's default settings put the CMD at 1T instead of 2T, resulting in failures in MemTest86+ 1.70 and regular lockups in WinPE environments, Win XP, and Windows Vista (build 5840). I know it's a new board and I've tried both the stock 0202 BIOS and the Asus beta 0401 BIOS that Asus support sent me. Neither provide proper clocking of the RAM by default and the inability to use it in 1T is rather disappointing, to say the least. Any news on this? I'd like to see if this is a known issue and, if so, what can be done to resolve it. Link to comment Share on other sites More sharing options...
DerekT Posted January 21, 2007 Share Posted January 21, 2007 Contrary to popular belief, the Command rate or Command Per Clock rate is NOT a memory timing, it is a memory controller transfer characteristic. The CPU and most types of memory have an 8 byte data transfer bus. They transfer 8 bytes of data once, twice, or four times per clock tick. However, for efficiency the basic unit of data transfer is a 32 byte "burst" of data around the address of the data the CPU needs. Any CPU reference to memory is rounded up to a complete 32 byte block. This block is transferred in a burst of 4 consecutive 8 byte transfers. Your timing settings effect this transfer, not the Command per clock. The Command Per Clock sets the Command Rate for the memory controller and new chipsets are often the most finicky about ram, and especially so with Nvidia's Northbridges. When they work, they are fast, but they seem to issue quite a few problems. Can you disable the EPP and set the timings and command rate manually? Link to comment Share on other sites More sharing options...
KalieMa Posted January 21, 2007 Author Share Posted January 21, 2007 Can you disable the EPP and set the timings and command rate manually? Luckily, I can do this. Whenever I have to clear the CMOS though, it sets it back to 1T, resulting in instability. I guess I'll just have to manually leave it at 2T whenever I clear the CMOS until a firmware update fixes things. The strange thing though is that several other users on other boards are having alot of success running DDR-800 RAM at 1T. The only people that seem to be having problems on this board are the XMS2 users. :( Link to comment Share on other sites More sharing options...
KalieMa Posted January 21, 2007 Author Share Posted January 21, 2007 I'll also note that I'm extremely disappointed that I paid a decent price premium for the XMS2 modules only to find out that the modules I recieved have the Promos chips on them instead of the quality Micron D9. This is alarmingly uncool. :( Link to comment Share on other sites More sharing options...
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