Importance of stepping for MP 1,1 CPU upgrades

Discussion in 'Mac Pro' started by Neodym, Aug 11, 2011.

  1. Neodym macrumors 68000

    Neodym

    Joined:
    Jul 5, 2002
    #1
    In all guides and postings i've read so far regarding the CPU upgrade inside a Mac Pro 1,1, noone is actually stressing the importance of the stepping to be considered before buying a new processor.

    For example - the popular X5355 (Quad-Core 2.66 GHz) is available in three flavours: SLAC4, SL9YM and SLAEG.

    All of those are reportedly running in the MP 1,1. There is an important difference between those, however:

    Only the SLAEG variant features the latest G0 stepping, which reduces the IDLE power by roughly 50%!

    The original 5150 Woodcrest processors (DualCore 2,66GHz) have an IDLE power of 24W, while the 5355 Clovertowns (QuadCore 2,66GHz) have an IDLE power of 50W in the older steppings, which is twice the amount and explains, why some people have to adjust fan speed with smcFancontrol to get rid of the additional heat (those are the ones w/o the G0/SLAEG stepping ;).

    With stepping G0 (to be found in the SLAEG variants) Intel about halved the power consumption in IDLE state, which brings the x5355 down to 25W, thus being nearly identical to the original 5150's 24W.

    Of course when fully under load, the Quadcores will sip significantly more power than the Dualcores (after all it's twice the amount of cores at work and that's why the TDP has been nearly doubled from 65W to 120W), but overall heat and power consumption should be significantly lower and closer to the "original" with the SLAEG x5355's.

    On the other hand, if you don't need more processing power, but want to save on the energy bill (i remember one member here from India being on UPS during regular blackouts), you could try to get the 5150's in G0 stepping ("SLAGA"), because the energy consumption in IDLE state is only 1/3rd (8W compared to the original 24W)!

    Interestingly enough, the x5365 is said to have the exactly identical IDLE power consumption as the x5355, which makes you wonder whether an x5355 is in fact nothing more than an artificially crippled x5365 (at least with G0 stepping - earlier steppings have a different TDP) that could be overclocked to 3,0GHz w/o any problem...

    Sources of information: Techreport.com, Wikipedia

    btw: Did anyone ever try to mix 5150 and 5355 to get a 6-core machine?
     
  2. MacinJosh macrumors 6502a

    Joined:
    Jan 29, 2006
    Location:
    Finland
    #2
    You can't mix different CPUs like that. IIRC you can mix a 5355 with a 5365 but they would both run at 2.66Ghz.
     
  3. somnbulance macrumors newbie

    Joined:
    Aug 12, 2011
    #3
    just curious, what if you mix between SLAC4, SL9YM and SLAEG? does it cause any issues or does one CPU just pull more power?
     
  4. MacinJosh macrumors 6502a

    Joined:
    Jan 29, 2006
    Location:
    Finland
    #4
    AFAIK TDP has to match as well so I would say no, it wouldn't work. It's all in Intel's sheet somewhere...
     
  5. 666sheep macrumors 68040

    666sheep

    Joined:
    Dec 7, 2009
    Location:
    Poland
    #5
    It just works ;) Search the forum, you'll find few reports of 1.1 upgrade with 2 CPUs with different steppings. No issues.

    See above and read this: http://ark.intel.com/products/28035
     
  6. somnbulance macrumors newbie

    Joined:
    Aug 12, 2011
  7. MacinJosh macrumors 6502a

    Joined:
    Jan 29, 2006
    Location:
    Finland
    #7
    Ok, TDPs match in those cases so I guess stepping is not an issue then.
     
  8. SirVikon macrumors newbie

    Joined:
    Aug 19, 2009
    #8
    So, my CPU X5355 will arrive on monday and i will upgrade my Mac Pro 1,1.

    I looked a couple of videos on YouTube and all people do different things with the Thermalpaste. Some do on Heatsinks and the cpu´s thermal paste, some only on the cpu, and some other ones make on both and then a line from left to the right in the middle of the cpu without elapsing the line ...

    What is the right to do?

    I have the G0 (SLAEG) and have bought me the arctic cooling MX4 paste. Do i really have to buy me some equipment against static electric?

    Sorry for my bad english, but i will hope that you can understand me ;)
     
  9. reebzor macrumors 6502a

    reebzor

    Joined:
    Jul 18, 2008
    Location:
    Philadelphia, PA
    #9
    Vertical line on the CPU only.

    See this for more info
     
  10. SirVikon macrumors newbie

    Joined:
    Aug 19, 2009
    #10
    I have the Arctic Cooling MX-4. I do nothing wrong, if i make it like the instruction for Arctic Silver or are there differences between them.
     
  11. Neodym thread starter macrumors 68000

    Neodym

    Joined:
    Jul 5, 2002
    #11
    There are generally differences regarding consistency of the various compounds, but any method can be viable if done correctly.
     

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