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 Post subject: AM3 power consumption in AM2 motherboard?
PostPosted: Thu May 06, 2010 9:42 am 
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Does anybody here know whether efficiency of the Socket AM3 CPUs is affected by running them in an older Socket AM2 board, such as my MSI K9AG Neo2-Digital?

I'm currently using an Athlon X2 BE-2350 (AM2) undervolted to 0.875V @1.0GHz, 1.075V @2.1GHz. This runs at just the right temperature with a Scythe Ninja being cooled by just the exhaust fan at 600RPM. When running at stock voltages there is too much heat and the fan needs to ramp up.

There are times when I just wish for a bit more speed, but I would be willing to sacrifice the speed if it means staying with the low temperatures (and hence noise). The new AM3 Athlon X2 such as the 240 and 250 look perfect on paper, but all reviews tested them in brand new AM3 boards, not an older board.


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PostPosted: Fri May 07, 2010 8:51 am 
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I recently dropped an AM3 Sempron 140 into an older Asus M2A-VM AM2 motherboard and my power usage dropped pretty significantly with some judicious undervolting. Prior to the Sempron, I was running a Brisbane 3600. The CPU is passively cooled with one 800 RPM exhaust and it runs perfectly cool and completely silent (HTPC application) even under load.

What is your system being used for?

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PostPosted: Sat May 08, 2010 2:08 am 
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Thanks, that's good to know. I had a look at your previous posts and see that you get nice low 30-40W idle power consumption with the Sempron. Do you have any numbers for how this compares with the X2 3600+?

This is for my HTPC, running Windows 7 Media Center and MediaBrowser.


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 Post subject: Re: AM3 power consumption in AM2 motherboard?
PostPosted: Sat May 15, 2010 9:39 am 
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Joined: Wed May 21, 2008 9:16 pm
Posts: 85
Location: Texas
CX23882-19 wrote:
Does anybody here know whether efficiency of the Socket AM3 CPUs is affected by running them in an older Socket AM2 board, such as my MSI K9AG Neo2-Digital?

I'm currently using an Athlon X2 BE-2350 (AM2) undervolted to 0.875V @1.0GHz, 1.075V @2.1GHz. This runs at just the right temperature with a Scythe Ninja being cooled by just the exhaust fan at 600RPM. When running at stock voltages there is too much heat and the fan needs to ramp up.

There are times when I just wish for a bit more speed, but I would be willing to sacrifice the speed if it means staying with the low temperatures (and hence noise). The new AM3 Athlon X2 such as the 240 and 250 look perfect on paper, but all reviews tested them in brand new AM3 boards, not an older board.


I think the main important thing to consider is how much electricity the particular motherboard chipsets use. I doubt there's a big efficiency difference relating to the processor, DDR3 used less voltage then DDR2 but it's a very very small difference. Off the top of my head I happen to know some of the lowest power boards are
1 anything by via
2 AMD 740G/760G
3 Nvidia 8200

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Wattage is 73W Idle, 205W Fully Loaded


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 Post subject:
PostPosted: Mon May 24, 2010 5:18 am 
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Joined: Sun Oct 09, 2005 3:37 am
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if you put an am3 chip into a am2 board (not an Am2+ board though) the am2 board doesn't support split plane voltage so it will use more power
as there isnt the lower voltage available.

so if you used say a am3 chip in a geforce 6100 board vs say a newer board like a 785g it would use a little more power.


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 Post subject:
PostPosted: Mon May 24, 2010 7:57 am 
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Location: Riga
I compared 760G to 785G, did not see any difference (at idle).
Split voltages are not that important, there is not much to gain, sometimes the two would be the same.
An AM2 board would mean slower hypertransport, less power.
Anyway, I think a newer CPU will give you more speed at the same temperature. I don't think there is any difference in power draw, AM2 versus AM3 boards (at the same voltage)


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 Post subject:
PostPosted: Wed Jun 02, 2010 12:29 pm 
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There is considerable power difference using a single vs. dual place board as the internal CPU component voltages are higher in the single plane along with the current draw on each CPU rail... nor do they support PSI, nor C1E, nor the lower P-States. The difference is lower however for the L3-less chips.


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 Post subject:
PostPosted: Wed Jun 02, 2010 4:25 pm 
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Location: USA
I also have a Asus M2A-VM (AM2) motherboard with a 4050e running at 2.1 GHz (stock speed). I would like to upgrade to a AMD Athlon II X2 240e 2.80 GHz (which is supported by the latest bios of my MB).

What CPU limitations will I encounter (in practical terms, not acronyms)? I don't care about the lower memory speed of my existing 4 GB of DDR2 memory (instead of DDR3 memory that AM3 boards can use).


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 Post subject:
PostPosted: Thu Jun 03, 2010 11:19 pm 
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My AM2+ Phenom II X4 runs 2.5GHz, 1.1375V CPU, 1.2V NB, draws 50W (load), at 1.2V would draw 58W. Separate power planes save me some 8W. It is quite a difference. But more common situation would be more GHz, CPU voltage more than NB voltage. There would be little difference, NB does not draw much. At idle separate power planes save me some 2W.
PSI can save me about 0.6W (idle). PSI is not about reducing CPU's draw, it is about reducing losses in the voltage regulation module by using less circuits when CPU voltage (and power) is reduced. Some AM2 boards support PSI.


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 Post subject:
PostPosted: Thu Aug 05, 2010 8:32 am 
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Joined: Mon Mar 21, 2005 11:18 am
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Location: Hessle
I finally pulled the trigger on a Phenom II X4 905e (low voltage version - reason being that I just wanted to plug it in and use it rather than mess around with undervolting).

I don't know what I was so worried about! Power consumption at idle seems no higher than the BE-2350 (~85W system with everything installed). I can't compare temperatures directly, since I have gone from a semi-passive Scythe Ninja Rev.B to a Noctua NH-C12P. I didn't want to use the Ninja Rev.B again - it seemed like a good idea at the time, but always felt "dangerous" (in terms of physical CPU damage during installation). The clips are ridiculously difficult to fasten in a cramped case such as my ECE-4252 and the last time I removed it, it ripped the CPU out of the socket. The original Ninja which I had on my S939 was much better.

Anyway. Even with the Noctua's 140mm fan running at 700RPM (the lowest I can do without hunting for a spare Zalman Fanmate) I can't get the CPU temperature above 35°C and that was with all 4 cores running flat-out. The BE-2350 with Ninja, even undervolted to 1.075V, was difficult to keep below 40°C. I suspect the Ninja's poor pressure more than the CPU though.

Full marks to MSI for adding Phenom II support to such an old board (I bought it in 2007). The Phenom II is correctly identified with the latest December 2009 BIOS and all voltages etc are correct. This motherboard was great value for money, although I must admit to getting frustrating with it in the early days due to various BIOS issues. MSI will be at the top of my list in the future.


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