Does RAM have anything to do with overclocking?

By SubKamran ยท 8 replies
Jan 22, 2004
  1. I was talking to a person on IRC (who was very rude by the way) and he said that memory doesn't have anything to do with overclocking your processor.

    I was wondering if this is true? And if it is, why do people make a big deal out of faster memory? Is it because if I buy a PC4200 it will be speedier and thus not be a bottleneck if I overclock a processor?
  2. Didou

    Didou Bowtie extraordinair! Posts: 4,274

    Well yes & no. For P4s where the multiplier is locked, you can only overclock with the FSB & in general that means also overclocking the memory.

    But then again, certain boards can run the Ram with a divider where even if you were to raise the FSB, you can use a divider to make the memory run at a lower speed.

    Here's an example :

    Let's say you have a P4 with a 200 FSB ( 800 ) & some PC3200 Ram. You run both in Sync so 200 FSB = 200 mhz for the Ram ( 400 ). That's what PC3200 is rated for, so no problems so far.

    If you start raising the FSB by 1mhz, the memory will follow & its speed will also go up by 1mhz. So if you get your FSB all the way to 250mhz ( 1000 ), you Ram will be running at 250mhz ( 500 ) putting it way beyond its rated speed ( it probably won't even do a POST ). In this case, you would need PC4000 Ram.

    Now, if your board has a 4/5 divider for the memory, you can set the FSB to 250mhz & the divider will keep the memory to 200mhz because ( 250 / 5 ) * 4 = 200mhz. In this case, your PC3200 Ram will work fine.

    Another matter is the amount of memory bandwidth. The P4 FSB at 200mhz ( 800 ) is capable of adressing 6.4 GB/s ( in theory ). PC3200 can deliver 3.2 GB/s. If you put them in a Dual Channel configuration, then 3.2 GB/s *2 -> 6.4 GB/s. In other words, it's exactly what the P4 needs. Now if you overclock the FSB to 250 ( 1000 ), the FSB can adress up to 8 GB/s ( once again in theory ) & if you keep the Ram at PC3200 in Dual Channel, it will still deliver 6.4 GB/s, thus you will loose some benefit from running a higer FSB. That's why it's better to keep the FSB in sync with the Ram even if you don't overclock.
  3. ---agissi---

    ---agissi--- TechSpot Paladin Posts: 1,978   +15

    Couldnt have said it better myself

    (der, thats didou ^^)
  4. SubKamran

    SubKamran TS Rookie Topic Starter Posts: 166

    Wow, thanks Didou :D

    Hopefully the RAM I bought will be suitable to run in sync up until a decent speed.
  5. PreservedSwine

    PreservedSwine TS Rookie Posts: 325

  6. farmer

    farmer TS Rookie Posts: 48

    I found that with the Asus P4P800 Dlx mobo, running async created a lot less problems, and with the better memory, could hit just as fasta speeds. In a perfect world, running the CPU and ram in sync would be the ideal, but it hasn't proven it for me...

  7. SubKamran

    SubKamran TS Rookie Topic Starter Posts: 166


    My CPU is entirely capable of running at 250Mhz FSB (3.1Ghz). Now, how do I set the ratio to "5:4"? My RAM is PC3200 and is running at 2-2-3-5.

    I'm running an Asus P4P800-Deluxe with a 2.4CGhz.
  8. SubKamran

    SubKamran TS Rookie Topic Starter Posts: 166

    I read that the "320" DRAM setting means a 5:4 divider...

    So, if I set the FSB to 250, and set the DRAM setting to 320, this will *hopefully* work? (I'm not at my computer...I'm at school ;) )
  9. farmer

    farmer TS Rookie Posts: 48

    Yes it should work. You set the fsb to 250, and your using the 5:4 divider, your ram is running at 200, which is stock speed. The ram you got should be able to do better than 200, so if your stable, try raising the fsb by 5, til you hit the wall...

    Good luck....
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