Does PAT function with asynchronous RAM?

Discussion in 'Abit' started by Metaphoid, Jul 11, 2003.

  1. Metaphoid

    Metaphoid Guest


    I've got a new Abit IC7 and have managed to overclock my 2.4C to 3.2Ghz with
    a fsb of 275 and PC3500 RAM running at 220 on a 5:4 ratio. Sounds like a
    perfectly good setup. However, some will have you believe that the
    performance boosting PAT function of the Canterwood chipset will only
    operate if RAM and CPU fsb speed are run synchronously. If I do this, I'll
    have to drop the fsb to 220 also, and hence the CPU will only be running at
    2.7Ghz or lower. I'd rather not do that.

    So, can anyone tell me whether or not PAT works with asynchronous memory,
    and whether the performance increase could even come close to justifying the
    necessary CPU speed drop.

    Metaphoid, Jul 11, 2003
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  2. Metaphoid

    Strafe Guest

    I haven't seen anything definitive. Some say PAT only works at 1:1, some say
    thats poppycock. One thing I do know is that Higher CPU speed is more
    important than memory speed.
    Strafe, Jul 11, 2003
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  3. Metaphoid

    Alceryes Guest

    Screw PAT!
    I'd turn it off and adjust the settings myself. You get much better results
    then PAT's 10-15% OC. From what I remember there are supposed to be 3 or 4
    different levels of PAT. Each higher level indicates a higher level of OC
    that PAT will go but I think the highest level only OC's by 10-15% (anyone
    confirm?). There's nothing special about's just automatic OC'ing.
    Oh and I think it will work sync or async, doesn't matter.

    "I don't cheat to survive. I cheat to LIVE!!"
    - Alceryes

    (check out my modded/OC'd system at
    Alceryes, Jul 11, 2003
  4. How did you arrive at that 90% value?
    David Maynard, Jul 12, 2003
  5. Metaphoid

    John Guest

    According to, with the 800 FSB cpu's on the 865/875
    chipsets, increasing CPU speed has a better effect on overall performance
    than increasing memory speed

    John, Jul 12, 2003
  6. Metaphoid

    TomG Guest

    I don't know which is more effective or important, raising cpu speed or
    memory bandwidth. I'd guess that one is no good without the other, myself.
    you can have the fastest cpu around but if it is just sitting there waiting
    on data, than it will not be doing anything. conversely, you can have the
    fattest memory pipe but it might well be empty.


    Thomas Geery
    Network+ certified Abit Mirror <----- Cable modem IP
    This IP is dynamic so it *could* change!...
    over 113,000 FTP users served!
    TomG, Jul 12, 2003
  7. Metaphoid

    Gaidheal Guest

    "How did you arrive at that 90% value?

    LOL I did not.. the people whose job it is to look at things like that did
    :¬) Why not do the same research I did to find it? Hehe!

    Conservative estimates have always been "50%" since the days of "crossing
    the 1GHz barrier".

    Of course, SOME applications are going to keep the CPU working more, but
    even there, the CPU is not the bottle neck, memory and other I/O devices
    are. A modern fast CPU spends a lot of time waiting for data to be
    retrieved from memory, even with improvements in cache technology,
    prefetching, etc.
    Gaidheal, Jul 12, 2003
  8. Metaphoid

    John Lewis Guest

    Depends on the application, doesn't it ?

    Running a complex MathCAD computation --- CPU
    Running a data-base sort ---------- memory

    John Lewis
    John Lewis, Jul 13, 2003
  9. Metaphoid

    TomG Guest



    Thomas Geery
    Network+ certified Abit Mirror <----- Cable modem IP
    This IP is dynamic so it *could* change!...
    over 113,000 FTP users served!
    TomG, Jul 13, 2003
  10. Which would be, who? Just because someone has a web site doesn't mean
    they are an 'expert' nor, no offense intended, do I know if you
    interpreted it correctly.
    Because, for one, I don't know what kind of search you did and, since
    you 'already did it', I would think you could provide the source.
    Again, I need a source for those "conservative estimates" to know who is
    making them, their qualifications to do so, the method they used to
    determine it, and precisely what it means.
    There IS a "lot of time" (whatever that means) spent 'waiting' for
    memory but one of the most significant chunks is memory latency, and no
    amount of 'bandwidth' will solve that (faster access times would help
    and longer memory streams would help [as in larger cache sizes, etc]).
    Which is but one example of what I mean by asking "what does it mean?"
    when a generic statement like "spends a lot of time waiting" is tossed
    out. e.g., if the 'time waiting' in the articles you read are due to
    memory latency then the suggestion to increase FSB vs processor speed
    isn't necessarily good as latency will remain the dominant factor.

    Just off hand, what you seem to be implying by "spends 90% of it's time
    waiting," and that it is due to the memory pipe bandwidth being maxed
    out, is contradicted by observable performance numbers. If it were true
    then increasing processor speed would have virtually no effect on
    performance as performance would be completely memory pipe bound (I.E.
    you're only able to execute as many instructions as come down the
    already speed limited pipe, which can't provide 'more' of them) and you
    would just be processing the previous 10% portion faster while waiting
    more. (This is analogous to the jackrabbit start dragster driving down a
    street where the lights are timed for 30 MPH. He just gets to the next
    stop light quicker [time spend 10%] and then waits at the next one
    longer [time spent 90%] than the more sedate driver. And him going
    faster just means he get's there quicker to wait longer. I.E. The "hurry
    up and wait" syndrome.)

    However, even memory intensive benchmarks (meaning high data throughput
    as well as instructions stressing the memory pipe) show corresponding
    performance increases with CPU speed (within the realm of currently
    available CPU to memory bandwidth ratios) so the memory pipe is
    apparently not 'maxed out' with the slower processor. Otherwise, anyone
    who buys more than the slowest, cheapest, processor available on any
    particular speed FSB is a fool as they get 'nothing', under your theory,
    for more processor speed.
    David Maynard, Jul 14, 2003
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