Desktop CPU Power Survey, April 2006

CPUs|Motherboards | Power
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TEST RESULTS

A. AT FULL LOAD

Prevailing conditions during testing were 20~21°C and 117~119VAC, measured with the Extech power meter.

Power Consumption at Full CPU Load
Processor
Platform
Clock Speed
Vcore
CPU Power* (DC)
System Power† (AC)
Stock
Min
Stock
Min
Stock
Min
Intel P-M 770 Dothan
479-1
2.13 GHz
1.30V
1.12V
23.3W
13.8W
65W
53W
AMD Turion 64 ML-40 Lancaster
754
2.2 GHz
1.22V
1.05V
26.4W
18.1W
64W
54W
Intel Core Duo T2600Yonah
479-2
2.16 GHz
1.26V
1.15V
25.4W
19.5W
78W‡
75W
AMD A64 3000+ Venice
939
1.8 GHz
1.39V
1.18V
31.9W
20.5W
74W
61W
AMD Sempron 3400+ Venice
754
2.0 GHz
1.39V
1.19V
38.9W
26.4W
82W
66W
AMD A64 3500+ Winchester
939
2.2 GHz
1.41V
1.24V
47.5W
31.6W
98W
80W
AMD A64 4000+ San Diego
939
2.4 GHz
1.39V
1.29V
42.8W
34.3W
88W
76W
AMD A64 3500+ Venice
939
2.2 GHz
1.41V
1.22V
53.8W
34.6W
104W
83W
AMD A64 X2 3800+ Toledo
939
2.0 GHz
1.39V
1.22V
58.0W
41.4W
109W
90W
AMD A64 X2 4800+ Toledo
939
2.4 GHz
1.37V
1.22V
87.3W
61.9W
144W
115W
Intel P4 630 Prescott
775-1
3.0 GHz
1.23V
1.23V
77.7W
77.7W
128W
128W
Intel P-D 820 Smithfield
775-1
2.8 GHz
1.31V
1.14V
124.0W
90.5W
181W
142W
Intel PD 930 Presler
775-2
3.0 GHz
1.22V
1.21V
93.6W
93.6W
146W
146W
Intel PD 950 Presler
775-2
3.4 GHz
1.22V
1.22V
105.1W
105.1W
160W
160W
Intel P4 670 Prescott
775-1
3.8 GHz
1.34V
1.34V
128.9W
127.7W
197W
195W

Notes for above table:
*CPU power includes losses in the motherboard voltage regulators. The power drawn by the CPU alone is probably ~20% lower.
The system power includes losses in PSU AC/DC conversion. At >100W AC, it is probably not much more than 20%. At <70W AC, the loss could be >30%.
System power on the Yonah platform is higher because it required an outboard PCIe graphics card. With an onboard graphics motherboard, it would be 10~15W lower.

The table above is ranked by CPU Power, with the lowest at the top. The top two-thirds of the table (<60W) contains only AMD processors and two mobile Intel processors. There is only one AMD processor, the X2-4800+, arguably the most high performance CPU in the entire group, that reaches 60W. Five Intel processors make the bottom ranks; the 670, a single core P4-3.8, requires more than double the power of the dual core X2 4800+.

This is not the result of us choosing processors to bias the test. The Intel 630, just about the slowest desktop P4 Intel offers at this time, draws more power than the AMD A64 X2 4800+, the second most powerful desktop processor AMD offers currently. To top it off, the 630 is a single core processor while the X2 4800+ is a dual core.

It is true that Celerons are missing while there is a Sempron in the mix. However, this would have made little difference. All the current 2.4~2.8 GHz Celerons have 60~68W TDP, while our Sempron 3400+ sample measured 31.9W including VRM losses. Also, retailers FrontierPC and NCIX in the Vancouver area reported that there was no demand for Celerons — and hardly any supply at this time.

B. AT IDLE

Power consumption at idle is similarly one-sided. At the top with 1~2.2W power consumption are the mobile processors. At the bottom are the Intel desktops at 21.6~33.6W. AMD desktop processor systems ranged from a low of 4.1W to a high of 9.8W, which is pretty narrow, given the performance range represented — Sempron 3400+ to X2 4800+.

Power Consumption at Idle
Processor
Platform
Clock Speed
CNQ / EIST
Vcore
CPU Power*
System Power†
Intel P-M 770 Dothan
479-1
800 MHz
yes
0.734V
1.0W
40W
Intel Core Duo T2600‡ Yonah
479-2
1.0 GHz
yes
0.95V
1.5W
53W‡
AMD T64 ML-40 Lancaster
754
800 MHz
yes
0.92V
2.2W
40W
AMD Sempron 3400+ Venice
754
1.0 GHz
yes
1.10V
4.1W
44W
AMD A64 3000+ Venice
939
1.0 GHz
yes
1.18V
4.8W
48W
AMD A64 X2 3800+ Toledo
939
1.0 GHz
yes
1.18V
5.6W
51W
AMD A64 4000+ San Diego
939
1.0 GHz
yes
1.18V
5.6W
51W
AMD A64 3500+ Winchester
939
1.0 GHz
yes
1.19V
8.1W
53W
AMD A64 X2 4800+ Toledo
939
1.0 GHz
yes
1.18V
8.8W
53W
AMD A64 3500+ Venice
939
1.0 GHz
yes
1.18V
9.8W
55W
Intel P4 630 Prescott
775
2.8 GHz
yes
1.23V
20.7W
64W
Intel PD 820 Smithfield
775
2.8 GHz
yes
1.17V
26.7W
71W
Intel PD 950 Presler**
775
2.4~3.4 GHz
yes
1.19V
6.4 / 31W
74W
Intel PD 930 Presler**
775
2.4~3.0 GHz
yes
1.22V
7.8 / 32W
75W
Intel P4 670 Prescott
775
3.8 GHz
yes
1.24V
33.6W
84W

Notes for above table:
*2x12V power includes losses in the motherboard voltage regulators. The power drawn by the CPU alone is probably ~20% lower.
† The system power includes losses in PSU AC/DC conversion. At >100W AC, it is probably not much more than 20%. At <70W AC, the loss could be >30%.
System power on the Yonah platform is higher because it required an outboard PCIe graphics card. With an onboard graphics motherboard, it would probably be just over 40W.
** The Intel Pentium D 930 and 950 idle power measurements
require some explanation. When our standard high precision LTS 25-NP Current Sensor was used to read the AUX12V current, very low <10W values were obtained. Using our old Fluke 36 Clamp Meter on the 12V leads gave us the second set of 31~32W readings, which are much more believable. It's an odd testing anomaly isolated only to these processors.

Idle CPU Voltage for the socket 939 processors could not be set below 1.18V on the ASUS A8N-VM CSM motherboard used for thiis platform, neither in the BIOS nor with any software utilities like Crystal CPU ID. Chances are very good that the idle Vcore could be considerably lower, and this would mean lower system power as well. Some SPCR forum members have reported fine operation with <1.0V idle C'n'Q Vcore on A64 processors.



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