The World's First 65 W Desktop Quad Core
1:30 AM - May 21, 2008 by Frank Voelkel
Introduction
As far as performance is concerned, AMD is lagging behind its competitor Intel. But few users other than gamers still care solely about performance. In this age of burgeoning energy prices, AMD has an ace up its sleeve: the world’s first quad core CPU that consumes as little as 65 W (TDP). In comparison, Intel’s smallest quad core absorbs 95 W (TDP), despite the fact that Intel is already using 45 nm technology and AMD is still at 65 nm.
In terms of power consumption, AMD’s platform as a whole — motherboard, CPU and graphics chip — is not bad either. Its performance is perfectly adequate for office work and entertainment, though not for games. The integrated graphics engine in the 780G chipset is capable of rendering Blu-ray movies in 1920 HD resolution under maximum CPU load without jitter via HDMI. With Intel, this is only possible with a separate graphics card, as a comparable platform is not yet available.
AMD still has difficulties with high clock frequencies. While Intel’s quad core easily touches the 3 GHz mark, AMD is barely capable of 2.5 GHz. The Phenom X4 9100e presented in this article operates at 1.8 GHz.
Compared to classic Athlon 64 X2 CPUs, the first Phenom models with the B2 stepping featured improved power efficiency, but due to a TLB error — largely irrelevant in practice — the maximum clock rate had to be limited to 2.30 GHz. The B3 stepping eliminated the error, allowing the clock rate to be pushed up to 2.50 GHz. As even the B3 update failed to provide a major boost to the clock rate of the Phenom core, AMD was forced to increase the core voltage. Thus, the Phenom X4 with the B3 stepping is characterized by an extremely high power consumption (TDP) of 125 W.
Nevertheless, Tom’s hardware test of Phenom X3 CPUs provides evidence that AMD is capable of reducing the Phenom’s power consumption by optimizing the production process. Using a core based on the B3 stepping, the voltage and current requirements are much lower compared to the quad-core models at the same clock rate.
The following sections will shed light on how AMD was able to set the bar at 65 W.
Like all Phenom CPUs, the 9100e is also produced via a 65 nm process. In terms of technical features, it is completely identical to the conventional Phenom X4 CPU; the only differences are clock rates and the supply voltage. On the low-power Phenom, the speed of the memory controller and Hypertransport protocol has been set to 1600 MHz. The standard Phenom X4 runs these components at 1800 MHz, while the Phenom X4 9850 Black Edition has a clock rate of 2000 MHz.
MC = memory controller, HTT = hypertransport link
The low-power model does not have an unlocked multiplier.
Core Voltage: only 1.10 V
The fact that the Phenom X4 9100e is a low-power CPU is evident from the core voltage: at full throttle, the quad core CPU gets by with 1.100 V.
The tool Core Temp reads out the VID of the 9100e CPU correctly. Evidently, the board manufacturers did not expect that AMD would introduce a Phenom CPU with such a low supply voltage to the market; on our MSI K9A2 Platinum board, the voltage cannot be adjusted manually. The VID is only set to 1.100 V if the board is set to auto. The board supplies the CPU with 1.096 V; at this supply voltage, CPU operation is absolutely stable.
The manual setting of the MSI board for the core voltage begins at 1.128 V.
The table shows the voltages used by our models.
If the Phenom 9100e enters the Cool’n’Quiet power-saving mode when idle, its core voltage drops from 1.10 V to 1.00 V.
In Cool’n’Quiet mode, the Phenom 9100e lowers its voltage to 1.00 V; the Phenom X3 reduces its supply voltage to 1.050 V.
By comparison, the Phenom X3, whose power loss is also much lower than that of the classic Phenom X4, reduces its voltage to 1.05 V.
Overclocking to 2.40 GHz: the Board Is the Limit
The Phenom 9100e has greater overclocking potential than the other Phenom X3 and X4 models. We were able to overclock the Phenom 9100e from its standard clock rate of 1.80 GHz to 2.40 GHz without increasing the core voltage.
At its original voltage of 1.100 V, the Phenom 9100e operates smoothly at 2.40 GHz.
There is, however, a slight hitch. As the Phenom 9100e has a fixed multiplier of 9x, it can only be overclocked by raising the front-side bus. To achieve a CPU rate of 2.40 GHz, we had to increase the FSB from 200 MHz to 266 MHz. This elevated FSB represents the limit for the AMD 790FX chipset with the SB700 southbridge. With a good portion of luck and by increasing all board voltages, some boards can be stepped up to 295 MHz. Most, though, are not stable enough for long-term operation in such a configuration.
When clocked to the level of a Phenom X4 9750, the power consumption of Phenom X4 9100e is fascinating — see the next page.
CPU Power Loss: 63.9 Watts Under Full Load
Our measurement confirms AMD’s TDP specifications. Under full load of all four CPU cores with Prime95, we measured a power consumption of 63.95 W. Our measurement also includes the power loss of the voltage stabilizers, so the Phenom X4 9100e actually consumes even less power.
In response to the many inquiries of our readers, we included Intel’s Core 2 Quad Q9450 in the power measurements. As we could only get hold of a 45 nm Intel CPU, the Core 2 Extreme QX9770, we simulated the Core 2 Quad Q9450. The freely selectable multiplier was set to 8.0 and the FSB to 333 MHz; the CPU’s core voltage was 1.2875 V. Our Core 2 Extreme QX9770 was a sample with C0 stepping.
Compared to the Phenom X3, which has one CPU core less, the low-power Phenom’s power consumption is approximately 10.5 W lower. Though the clock rate of the 9100e is 300 MHz below that of the Phenom X3, it also consumes less power at the same clock rate.
Compared to the other Phenom X4 CPUs, AMD’s Phenom 9100e succeeds in saving the power consumption equivalent of one CPU core.
For more detailed information, please go to the link below. :D
Source: Toms Hardware
Labels: AMD, Intel, Phenom |
