Is DDR worth it?

bigcbigc
Posted:
in Future Apple Hardware edited January 2014
10% to 20% gain doesn't seem worth it. Apple is probably on the right track with DDR cache.



<a href="http://www6.tomshardware.com/mainboard/00q4/001030/athlon-15.html"; target="_blank">DDR speed</a>
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Comments

  • Reply 1 of 34
    wheewhee Posts: 46member
    [quote]Originally posted by Bigc:

    <strong>10% to 20% gain doesn't seem worth it. Apple is probably on the right track with DDR cache.



    <a href="http://www6.tomshardware.com/mainboard/00q4/001030/athlon-15.html"; target="_blank">DDR speed</a></strong><hr></blockquote>



    ... not worth it? Was the 25% MHz boost going from a 800MHz G4 to a 1GHz G4 "not worth it"? Is it not worth shaving an entire day off of a memory-intensive computation that would otherwise take a full week? Adding DDR support isn't the most complicated operation in the world. It has been done before, used mainstream for quite a while, and its operation is well known for those who care.



    These "small" performance gains all add up. The computing industry as a whole would be going nowhere if developments such as these were not taking place.



    So yes, it's worth it.
  • Reply 2 of 34
    luciferlucifer Posts: 2member
    [quote]Originally posted by whee:

    <strong>



    ... not worth it? Was the 25% MHz boost going from a 800MHz G4 to a 1GHz G4 "not worth it"? Is it not worth shaving an entire day off of a memory-intensive computation that would otherwise take a full week? Adding DDR support isn't the most complicated operation in the world. It has been done before, used mainstream for quite a while, and its operation is well known for those who care.



    These "small" performance gains all add up. The computing industry as a whole would be going nowhere if developments such as these were not taking place.



    So yes, it's worth it.</strong><hr></blockquote>
  • Reply 3 of 34
    mattyjmattyj Posts: 898member
    DDR is important, but mainly for memory bandwidth, this is all important in apps like games, and this is why macs fall behind so badly in Quake 3 framerates etc. So it is needed, if not mostly from a market point of view.
  • Reply 4 of 34
    spartspart Posts: 2,060member
    [quote]Originally posted by Lucifer:

    [QB][/QB]<hr></blockquote>



    You quoted him yet said nothing...wtf?
  • Reply 5 of 34
    matt hansonmatt hanson Posts: 4member
    Yes, DDR is worth it. Apple has to keep up with the times -- I am not saying they are not (bluetooth is off the hizzy!), but, if the GeForce has it I think the mobo should too. Just because they have protected memory doesnt mean they can stay behind hardware wise.
  • Reply 6 of 34
    brussellbrussell Posts: 9,812member
    [quote]Originally posted by Spart:

    <strong>



    You quoted him yet said nothing...wtf?</strong><hr></blockquote>
  • Reply 7 of 34
    horned_froghorned_frog Posts: 577member
    [quote]Originally posted by Spart:

    <strong>



    You quoted him yet said nothing...wtf?</strong><hr></blockquote>



    I see this quite a bit around here. Always makes me scratch my head!
  • Reply 8 of 34
    outsideroutsider Posts: 6,008member
    I think it's a way of saying "what he said".



    On topic, DDR needs to be well implimented to be of any use. Modern G4's don't have the ability to make full use of all the bandwidth so... until they do.
  • Reply 9 of 34
    bigcbigc Posts: 1,224member
    [quote]Originally posted by Outsider:

    <strong>I think it's a way of saying "what he said".



    On topic, DDR needs to be well implimented to be of any use. Modern G4's don't have the ability to make full use of all the bandwidth so... until they do.</strong><hr></blockquote>



    Apple didn't institute write combining til last year.
  • Reply 10 of 34
    r-ager-age Posts: 21member
    found this at ramjet <a href="http://www.ramjet.com/g42001.asp"; target="_blank">http://www.ramjet.com/g42001.asp</a>;

    is this true?



    CAS Latency:

    For the 512mb PC-133 DIMM for G4, there is no such thing as a CL2 IC chip. Any claim by a manufacturer or reseller that they have CL2 512's is actually false. They are reprogramming the SPD chip on the module to tell the computer that the RAM is CL2, but it is still CL3 RAM, and it will not perform any faster. This is why Apple's spec calls for CL3 RAM in the G4.



    when will we see true CL2 512MB DIMMs?
  • Reply 11 of 34
    r-ager-age Posts: 21member
    opps...2



    [ 03-28-2002: Message edited by: R-age ]</p>
  • Reply 12 of 34
    bodhibodhi Posts: 1,424member
    Write Combining was instituted with the 466, 533, 667 & 733 machines.



    Is DDR worth it? Is double the bus speed worth it? Considering that AltiVec and the processor is spending most of it's time waiting for info I think DDR will bring incredible increases in performance.
  • Reply 13 of 34
    outsideroutsider Posts: 6,008member
    The bottleneck is the 64bit 133MHz MPX bus of the G4. No matter how you slice it, even if you somehow eliminated packet overhead you could NEVER exceed 1.0 GB per second! How hard is that to understand? Until MPX support over 133MHz or supports DDR interface PC133 will be enough for the implimentation Apple uses. Apple COULD run the G4 out of spec but that's like selling overclocked processors. Apple's not going to do it.
  • Reply 14 of 34
    programmerprogrammer Posts: 3,458member
    - Write combining was introduced with the 7450, the 7400/7410 don't have it. This is part of the processor, so it was up to Motorola to add it, not Apple.

    - The quoted 10-20% performance increase is on generalized benchmarks. Some operations will see a 100% performance increase (especially media processing type algorithms).

    - People are correct in pointing out that DDR isn't possible until a revised G4 with a faster bus interface arrives. This depends on Motorola.

    - Is DDR worth what? It isn't noticably more expensive than SDRAM now, and once the DDR chipset is designed it isn't going to be any more expensive to produce than the current chipsets. So there is minimal cost for appreciable gain.
  • Reply 15 of 34
    bigcbigc Posts: 1,224member
    [quote]Originally posted by Programmer:

    <strong>- Write combining was introduced with the 7450, the 7400/7410 don't have it. This is part of the processor, so it was up to Motorola to add it, not Apple.

    - The quoted 10-20% performance increase is on generalized benchmarks. Some operations will see a 100% performance increase (especially media processing type algorithms).

    - People are correct in pointing out that DDR isn't possible until a revised G4 with a faster bus interface arrives. This depends on Motorola.

    - Is DDR worth what? It isn't noticably more expensive than SDRAM now, and once the DDR chipset is designed it isn't going to be any more expensive to produce than the current chipsets. So there is minimal cost for appreciable gain.</strong><hr></blockquote>



    It wouldn't hurt to have it but is it worth a motherboard redesign (given that the x86 MB DDR implementation seems to have various results in speed depending on chipset).



    As to media processing algorithms MPEG-4 decoding doesn't seem to be much faster (&lt;0.075%).



    <a href="http://www6.tomshardware.com/mainboard/00q4/001030/athlon-18.html"; target="_blank">http://www6.tomshardware.com/mainboard/00q4/001030/athlon-18.html</a>;



    (sorry paste into url link don't work )
  • Reply 16 of 34
    derrick 61derrick 61 Posts: 178member
    [quote]Originally posted by R-age:

    <strong>CAS Latency:

    For the 512mb PC-133 DIMM for G4, there is no such thing as a CL2 IC chip. Any claim by a manufacturer or reseller that they have CL2 512's is actually false. They are reprogramming the SPD chip on the module to tell the computer that the RAM is CL2, but it is still CL3 RAM, and it will not perform any faster. This is why Apple's spec calls for CL3 RAM in the G4.



    when will we see true CL2 512MB DIMMs?</strong><hr></blockquote>



    My question: What is the difference between "CL2" and "CL3" RAM? <img src="confused.gif" border="0">
  • Reply 17 of 34
    bigcbigc Posts: 1,224member
    [quote]Originally posted by Derrick 61:

    <strong>



    My question: What is the difference between "CL2" and "CL3" RAM? :confused: </strong><hr></blockquote>



    <a href="http://www.sysopt.com/articles/latency/"; target="_blank">http://www.sysopt.com/articles/latency/</a>;
  • Reply 18 of 34
    programmerprogrammer Posts: 3,458member
    [quote]Originally posted by Bigc:

    <strong>It wouldn't hurt to have it but is it worth a motherboard redesign (given that the x86 MB DDR implementation seems to have various results in speed depending on chipset).</strong><hr></blockquote>



    Hopefully Apple would do a good implementation. Their current SDRAM implementation is quite good, so it isn't unreasonable to believe that they could add DDR support with good results.



    [quote]<strong>As to media processing algorithms MPEG-4 decoding doesn't seem to be much faster (&lt;0.075%).



    <a href="http://www6.tomshardware.com/mainboard/00q4/001030/athlon-18.html"; target="_blank">http://www6.tomshardware.com/mainboard/00q4/001030/athlon-18.html</a></strong><hr></blockquote>;



    This is encoding which is typically completely CPU bound, not memory bound. MPEG encoding is a fairly intensive process which uses only a couple of frames worth of memory at once so it'll usually fit in the caches pretty well. A better example of memory bound processes would be image filters on large images, but there are many others.
  • Reply 19 of 34
    outsideroutsider Posts: 6,008member
    The G4 would need major modifications to use a DDR bus. The easiest way is for them to design a SDR bus that operates at a higher frequency. 200MHz would give you 1.6GB per sec and then using PC2100 RAM would make more sense.
  • Reply 20 of 34
    mattyjmattyj Posts: 898member
    Maybe the G4 won't have DDR implemented at all, at least in the PowerMac series. Perhaps Apple decided not to push DDR into G4 macs because the G5 is not that far round the corner, and that will use DDR 333Mhz RAM from what I've heard. I'm not saying it is, it could just be a possibility.



    Oh well, I can dream.... <img src="graemlins/lol.gif" border="0" alt="[Laughing]" />
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