Difference between FSB and actual Bus Speed?

By nico1606 ยท 11 replies
May 27, 2004
  1. Title pretty much sums up the question.

    As of right now i have a FSB of 133 and a Bus Speed of 266.

    I thought they were both the same?

    On a side note, my multiplier is 12.5...I thought it was supposed to stay at 10, unless you're overclocking it...which I'm not.

    Specs are:
    Giga-byte GA7-VAX KT400 chipset
    AMD Athlon XP 2000
  2. Vehementi

    Vehementi TechSpot Paladin Posts: 2,704

    They are the same. Read up on DDR to find out why.
  3. nico1606

    nico1606 TS Rookie Topic Starter Posts: 29

    Well see, that's my whole reason for posting the question here....
  4. Rory7

    Rory7 TS Rookie Posts: 119

    So your saying you can't be bothered reading up on what DDR is? Well it means double speed, only put into words that begin with D D and R. So normal RAM running at say 200mhz is turned into DDR 400. The number is doubled, resulting in more speed.

    Also if your multiplyer is running at 12.5 when it should be at 10 and its stable, what are you bitching about? You have a faster pc than you thought you had, so thumbs up.
  5. Arris

    Arris TS Evangelist Posts: 4,731   +379

  6. nico1606

    nico1606 TS Rookie Topic Starter Posts: 29

    I realize what DDR Ram is, what I'm saying is how does that tie into my FSB or Bus Speed?

    And for the record, I wasn't bitching about my speed, just was curious.

    Hold on .. I think I get it now.

    Since DDR Ram runs twice per cycle it basically doubles the speed of the bus.. So Since I have a 133 FSB... x2 would give me 266...
  7. Rory7

    Rory7 TS Rookie Posts: 119

    Sorry, i didnt mean to offend you, its just my way of speaking. As far as i know, your RAM doesnt have much to do with your bus speed. I think AMD's are double pumped, which is sort of like a DDR, only on your chip. So if somthing says it has a fsb speed of 400, it has bus speed of 200. When you are talking about your memory with your chipset, well they do work togeather, and you have to work out memory ratios when overclocking. So if you have a 400fsb on your chip, and you have DDR 400 on your memory, then they work in a 1:1 ratio, and should work quite nicely togeather. Say you have a different speed RAM, say DDR 333, you would have to work out a Ratio, for them to work nicely, say like 2:1 or somthing. So its important to get good, high frequency memory when overclocking, since it comes into play.

    Now i may be wrong here, im not an AMD person, not much AMD savvy. I do know that AMD's are double pumped, and Pentiums are quad pumped, for example i had a fsb of 533, and have a buss speed of 133.
  8. nico1606

    nico1606 TS Rookie Topic Starter Posts: 29

    Yea I think you're pretty much right on target except the Bus Speed seems to be 2x the FSB (since I have an AMD)

    133 x 2 = 266
  9. Rory7

    Rory7 TS Rookie Posts: 119

    yeah, 'double pumped'
  10. somekid007

    somekid007 TS Rookie Posts: 271

    Bus speed = actual rate
    FSB = effective rate

    ex1: Pentium $ Northwood C processors, 200Mhz ACTUAL BUS SPEED, quad pumped to 800MHz EFFECTIVE FSB SPEED

    ex1: Athlon XP Barton Processors, 166MHz or 200MHz ACTUAL BUS SPEEDS, double pumped to 333MHz or 400MHz EFFECTIVE FSB SPEED

    ex3: Athlon64 processosr, 800MHz ACTUAL BUS SPEED, dual pumped to 1600MHz EFFECTIVE FSB SPEED
  11. nico1606

    nico1606 TS Rookie Topic Starter Posts: 29

    I believe the Athlon 64 is actually a 400 FSB and 800 Bus Speed.
  12. ---agissi---

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

    Yeah, same here, (for the A64), 400 >> 800 ;)
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