If the Dual 2Ghz G5 CPU's are upgraded, what will happen to the system bus?

fulmerfulmer
Posted:
in Current Mac Hardware edited January 2014
I know this is a little premature since the dual 2Ghz is already fast and there are currently no replacement CPU's available, but the other day I saw the German guys website where he completely took apart his G5 and it got me started thinking. I noticed that the CPU's are using a socket to connect the daughter card to the motherboard similar to the G4's. If the CPU's are upgradeable like the G4's then will the system bus also be bumped up? Or will it stay the same (1Ghz)?



Just a little forward thinking...

Comments

  • Reply 1 of 16
    smithjoelsmithjoel Posts: 240member
    It will stay the same.
  • Reply 2 of 16
    baumanbauman Posts: 1,248member
    Really? I've always heard that the bus is fixed at half the speed of the processor. Now, I don't know what kind of voodoo magic needs to happen when you upgrade it, but I would thing that it would need to increase just to keep the G5s happy.
  • Reply 3 of 16
    billybobskybillybobsky Posts: 1,914member
    isnt the bus run by a crippled 970?
  • Reply 4 of 16
    smalmsmalm Posts: 677member
    The bus ratio in a G5 is 4:1 at the moment. The 970 can handle 2:1, 3:1, 4:1 and 6:1. So you might see a 3GHz upgrade some day from Sonnet that uses the 6:1 bus ratio. Expect prices to be unsane

    Or perhaps the 970FX and its successors can handle more/other bus ratios.
  • Reply 5 of 16
    maclogicmaclogic Posts: 35member
    Quote:

    Originally posted by smalM

    The bus ratio in a G5 is 4:1 at the moment.



    I thought it was 2:1?
  • Reply 6 of 16
    cosmocosmo Posts: 662member
    Quote:

    Originally posted by maclogic

    I thought it was 2:1?



    It is.
  • Reply 7 of 16
    outsideroutsider Posts: 6,008member
    Well technically it IS 4:1 but the bus is also run at DDR so the end result is 2:1.



    But 2:1, 3:1, 4:1 and 6:1 are the ratios the 970 support. The 970FX or other later 970's may support more ratios. Who knows.
  • Reply 8 of 16
    stoostoo Posts: 1,490member
    So that's 2:1 as in effectively 1:1 if you take into account DDR ? Interesting, from a power saving point of view (i.e. running the CPU slower, rather than the bus faster).
  • Reply 9 of 16
    airslufairsluf Posts: 1,861member
    Kickaha and Amorph couldn't moderate themselves out of a paper bag. Abdicate responsibility and succumb to idiocy. Two years of letting a member make personal attacks against others, then stepping aside when someone won't put up with it. Not only that but go ahead and shut down my posting priviledges but not the one making the attacks. Not even the common decency to abide by their warning (afer three days of absorbing personal attacks with no mods in sight), just shut my posting down and then say it might happen later if a certian line is crossed. Bullshit flag is flying, I won't abide by lying and coddling of liars who go off-site, create accounts differing in a single letter from my handle with the express purpose to decieve and then claim here that I did it. Everyone be warned, kim kap sol is a lying, deceitful poster.



    Now I guess they should have banned me rather than just shut off posting priviledges, because kickaha and Amorph definitely aren't going to like being called to task when they thought they had it all ignored *cough* *cough* I mean under control. Just a couple o' tools.



    Don't worry, as soon as my work resetting my posts is done I'll disappear forever.
  • Reply 10 of 16
    big macbig mac Posts: 480member
    Does anyone know whether or not Apple has placed any proprietary hardware on the G5 CPU daughtercards? In the past Apple has made it more difficult for upgrade card manufacturers to upgrade certain machines by placing ROM chips on the cards. I do realize Macs are far less reliant on physical ROM than they used to be, but something tells me there's probably an OpenFirmware chip on board some place.
  • Reply 11 of 16
    smalmsmalm Posts: 677member
    Quote:

    Originally posted by AirSluf

    No, the front side bus is 2:1.



    The memory is double channel DDR (hence the need to upgrade in pairs of DIMMS), the double channel aspect ups the throughput between the memory and system controller so it is not considered a further 2:1 reduction. It's all about bandwidth numbers, not the latency.



    In a 2GHz G5 the FSB runs at 500MHz - there's one channel for read and one for write only for each cpu. It is double pumped, so it's called 1GHz.

    As with all DDR (or QDR as in the P4) buses doubling the speed declaration is a marketing trick. DDR does not virtually double the speed of a bus - it would be better to say it virtually doubles the width of a bus.

    Read the article about SDR and DDR at ars technica "understanding bandwidth and latency".
  • Reply 12 of 16
    airslufairsluf Posts: 1,861member
    Kickaha and Amorph couldn't moderate themselves out of a paper bag. Abdicate responsibility and succumb to idiocy. Two years of letting a member make personal attacks against others, then stepping aside when someone won't put up with it. Not only that but go ahead and shut down my posting priviledges but not the one making the attacks. Not even the common decency to abide by their warning (afer three days of absorbing personal attacks with no mods in sight), just shut my posting down and then say it might happen later if a certian line is crossed. Bullshit flag is flying, I won't abide by lying and coddling of liars who go off-site, create accounts differing in a single letter from my handle with the express purpose to decieve and then claim here that I did it. Everyone be warned, kim kap sol is a lying, deceitful poster.



    Now I guess they should have banned me rather than just shut off posting priviledges, because kickaha and Amorph definitely aren't going to like being called to task when they thought they had it all ignored *cough* *cough* I mean under control. Just a couple o' tools.



    Don't worry, as soon as my work resetting my posts is done I'll disappear forever.
  • Reply 13 of 16
    smalmsmalm Posts: 677member
    AirSluf, I really don?t get it.

    In a 2GHz G5 the FSB runs at 500MHz which is a quarter of 2GHz so it's a bus ratio of 4:1.

    Anything else doesn't matter. Not that the bus is double pumped and not that there is one way out and one way in.



    And thanks a lot for your advice!
  • Reply 14 of 16
    macusersmacusers Posts: 840member
    Quote:

    Originally posted by smalM

    AirSluf, I really don?t get it.

    In a 2GHz G5 the FSB runs at 500MHz which is a quarter of 2GHz so it's a bus ratio of 4:1.

    Anything else doesn't matter. Not that the bus is double pumped and not that there is one way out and one way in.



    And thanks a lot for your advice!



    It is 4:1 but it doubles... 2:1
  • Reply 15 of 16
    123123 Posts: 278member
    The G5's FSB is clocked at 500MHz. The processor runs at 2000MHz. Obviously, 4:1 clock multiplication is used, effective speed is irrelevant. Please back up your claims that the posted ratios refer to effective clock rates (source?). If so, then the actual ratios would be 4:1, 6:1, 8:1 and 12:1 but I doubt that.
  • Reply 16 of 16
    123123 Posts: 278member
    Quote:

    Originally posted by AirSluf

    But that doesn't make the current FSB 4:1 when using correct technical descriptions,



    Bullshit.
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