RDRAM help...

jdcraunjdcraun
edited October 2006 in Hardware
I have a Dimension 8250 and am looking for an affordable RAM upgrade. It has modules of PC1066 RDRAM 256MBx2. I want to get it up to a gig but don't want to spend the dough on 526MB of PC1066. I was wondering if I can put PC800 in the other two modules or maybe even some kind of DDR SDRAM. I know it needs to be in a pair but that's about it. I have read some talk of latency or something... what is the best combo or would I just be better off getting 256MB module of PC1066 or does that have to be in a pair to and have to get two 128MB PC1066???

And my FSB runs at 533MHz...

Any help on what might be the best choice would be apprecitated. :bigggrin:

Comments

  • ThraxThrax 🐌 Austin, TX Icrontian
    edited October 2006
    You can put PC800, but you'll downclock your processor by 66*(Your CPU's multiplier). RDRAM needs to be paired, and no you can't use DDR.

    //EDIT: Fuzzy math.
  • jdcraunjdcraun
    edited October 2006
    So my processor would slow by 33%... ouch!
  • ThraxThrax 🐌 Austin, TX Icrontian
    edited October 2006
    PC800 = 200MHz FSB * 4. Your CPU speed with PC800 = (Multiplier * 200). With 1066, it's 266MHz FSB, so your CPU is (Multiplier * 266). Moving from PC1066 to PC800 means your FSB speed drops by 66MHz. So, your CPU speed on a 1066-designed CPU with PC800 is the (CPU Multi * 200) instead of 266.

    My initial math was fuzzy, but it's even more dire than I first said.
  • muddocktormuddocktor
    edited October 2006
    Actually, no, PC800 RDRAM won't downclock his processor, Thrax. It will downclock the ram speed to 800 MHz though, but won't mess with his fsb speed on the board.

    jdcraun, I would suggest that you seriously consider a mobo and processor and ram upgrade though, or at lest a mobo and ram upgrade. Unless you plan to find some PC800 RDRAM on eBay and get a good deal on it, that ram you are talking about getting is a big hunk of money for what you get. 2 X 256 MB sticks of Samsung PC800 is selling for around $170 plus shipping at Newegg. I hate to see someone pouring that kind of money into an old, seriously outdated system. :(

    EDIT: Thrax, it don't work that way with RDRAM. They have divisors in the board to run the ram at it's proper speed.
  • TheLostSwedeTheLostSwede Trondheim, Norway Icrontian
    edited October 2006
    Mudd,

    Sure about the dividers on those old boards?
  • muddocktormuddocktor
    edited October 2006
    I am sure that the ram's speed isn't tied into the fsb speed on the RDRAM chipsets made by Intel, TLS. I have some experience with the i820 chipset via my brother's old Dell P3 abortion he still has (now his son's computer). When the i820 chipset first came out, it was specc'ed for running PC600-PC800 ram with up to a 133 fsb chip. And back then RDRAM was rediculously expensive, with a 256 MB stick of PC800 costing around $1000. So Dell dressed out their machines with either PC600 or PC700 RDRAM for the normal configuration and an upgrade to actual PC800 stuff costing some atrocious amount. But his system would run at 866 MHz regardless of the speed ram used. I think it has something to do with the serial nature of RDRAM letting communication between MCH, ram and cpu operate totally independently. About 2 years ago I did do a memory upgrade on that old system and bought him a 256 MB stick of PC800 and I actually tried looking at the performance difference between his stock 256 stick of PC700 and the stick of PC800 I bought. It was actually a minimal performance hit between the 2, but in both instances the processor still ran at 866 MHz. So I just plugged both sticks of ram into his board and the board ran the memory at PC700 speeds, since that was the slower ram's capacity. BTW, the i820 chipset was a single channel version of the i840 and later i850 & 850E chipsets, so it only needed to popullate 1 channel with ram instead of 2 like all the rest.
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