Desktop CPU Power Survey, April 2006

CPUs|Motherboards | Power
Viewing page 7 of 8 pages. Previous 1 2 3 4 5 6 7 8 Next

F. WHAT ABOUT TURION 64 VS. ATHLON 64?

Our original article about the Turion 64 on the Desktop examined the this AMD mobile chip as a lower cost alternative to the Intel Pentium M. One of the often-repeated questions that came up after the Turion 64 article was,

"How does the Turion 64 fare against the latest Athlon 64s, in terms of power efficiency, computing power, ease of use on the desktop and price?"

This article was started originally to answer the above question. We have enough data to answer it. Please consider the summary table below. Note that all the figures are based on minimum stable CPU voltages; they are the lowest power numbers we could obtain in the systems we assembled.

Turion 64 versus Athlon 64
Processor
Price
Platform
Max Clock
CPU Power* (DC)
System Power† (AC)
Avg. Power
Idle
Load
Idle
Load
AMD Turion 64 ML-40 Lancaster
$268
754
2.2 GHz
2.2W
18.1W
40W
54W
41.4W
AMD A64 3000+ Venice
$140
939
1.8 GHz
4.8W
20.5W
48W
61W
49.3W
AMD A64 4000+ San Diego
$341
939
2.4 GHz
5.6W
34.3W
51W
76W
53.5W
AMD A64 X2 3800+ Toledo
$301
939
2.2 GHz
5.6W
34.6W
51W
83W
54.9W

1. NOISE

A major reason for seeking out low power CPUs is that they can be cooled more easily with less noise than the high power ones. The T64 ML40 has an idle power of just 2.2W and full load power of 18.1W. With an appropriately large heatsink optimized for low airflow, this CPU could probably be cooled just by a low speed fan in an efficient power supply — assuming a minimalist system with few heat producing parts, with the CPU placed close to the PSU, as is the norm in most case layouts.

Can a similar performance Athlon 64 be cooled passively? At idle, yes, but at extended full load, probably not except for the A64 3000+. The other A64 models exceed 30W at full load, and they would probably need a little more cooling, either an extra case exhaust fan on the back panel near the heatsink, or a fan directly on the CPU heatsink. But the airflow could be kept very low. The noise difference between a T64 system with one fan in the PSU versus an A64 system with an additional very quiet fan on the CPU might be inaudible in many environments for many users. We could be talking about as little as a 1~2 dBA@1m difference. When you consider that a dual core X2 3800+ is in the mix, the added performance might well be a worth the price of a 1~2 dBA noise increase. Pricewise, the cost of the X2 is just 10% more.

If the A64 3000+ Venice was overclocked to 2.0~2.2 GHz to match the performance of the T64 ML-40, we could expect the CPU power at load to go up to 25W. This might still be cool enough for passive cooling with a big heatsink like the Scythe Ninja. But the problem is that it's unlikely that this clock speed would be reachable while the CPU was undervolted as it has been to reach the 20.5W mark at 1.8 GHz. Raise the Vcore back up to default while overclocking to 2.2 GHz, and we're probably at 30W, which is not a realistic passive cooling target.

2. POWER

The relevant data to examine is the AC power consumption. The 54W full load power of the T64 system is impossible for the others to match. They don't even come close. The A64 3000+ idle power is 8W higher, and the others are 11W higher. If you look at the big picture, however, the energy consumption difference between the T64 and the X2 3800+ is not 30W; it is 13.5W average power, which is very small. This is assuming you use your computer much like most users do, in idle mode 90% of the time.

Even looked at only in average power terms, there seems no way the A64s can match the miserly T64. But they are not that far off. Compared to the 41.4W average of the T64 system, the others consume 19%, 29% and 33% more energy. The decision about whether the extra energy savings or extra performance is preferable is ultimately a personal one: It's your choice.

G. THE NEW PENTIUM D 930 & 950

These new dual cores may be the last of Intel's Netburst technology that began with the original P4. They differ from the 800 series in a number ways. Here's a three-way comparison.

Feature
Intel 900
Intel 800
AMD A64 X2
Core
Presler / 65nm
Smithfield / 90nm
Manchester, Toledo / 90nm
Clock
2.8 - 3.4 GHz
2.8 - 3.2 GHz
2.0 - 2.4 GHz
FSB
800 MHz
800 MHz
HyperTransport
1 GHz
Cache
L1: 24+32KB, L2: 2MB per core
L1: 24+32KB, L2: 1MB per core
L1: 128KB, L2: 512KB or 1MB per core
Memory Controller
n/a
n/a
Integrated on-die, dual ch DDR-400
Dynamic clocking
EIST
EIST
CnQ
64-bit
yes
yes
yes
Other
Virtualization, SSE 2/3, NX Bit Support
SSE 2/3, NX Bit Support
SSE 2/3, NX Bit Support

A primary difference between the Pentium Ds and the A64 X2 is that the former has two separate cores in one package while the latter has a fully integrated die with two cores within it. The Pentium D cores use the shared FSB to communicate with the memory controller located on the motherboard, which means worse memory latency and inability for the cores to communicate directly. The on-die memory controller of the Athlon 64 X2 has none of these limitations.

The big news with the 900 series is that it's on a smaller 65nm die with 376 million transistors compared to the 800 series' 90nm and 230 million transistors. There's also been extensive optimizations to reduce idle power consumption as much as possible. These refinements do help the 900s to outperform the 800s while drawing at bit less power. Unfortunately, the improvement is not enough to match to the energy efficiency of the AMD X2 processors.

Intel Pentium D
Processor
Price
Clock
CPU Power* (DC)
System Power† (AC)
Avg. Power
Idle
Load
Idle
Load
Intel D 820
$241
2.8 GHz
26.7W
90.5W
71W
142W
78.1W
Intel D 930
$316
3.0 GHz
31W
93.6W
75W
146W
82.1W
Intel D 950
$637
3.4 GHz
32W
105.1W
74W
160W
82.6W
AMD A64 X2 4800+
$643
2.4 GHz
8.8W
61.9W
53W
115W
59.2W

The 930 and 950 were somewhat hampered in this comparison by a motherboard that locked the Vcore. The only board on hand that supported these processors was the Intel D945GTP. It was not an ideal test bed because of a very limited BIOS and lack of support for Windows-based clock-speed and Vcore utilities. It is very possible that these processors could have run with a touch less Vcore, perhaps 0.1V, which would have been enough to drop the load CPU power by at least 5W and the system power by as much as 8~10W.



Previous 1 2 3 4 5 6 7 8 Next

Power - Article Index
Help support this site, buy from one of our affiliate retailers!
Search: