When it comes to selecting the components for your home theatre PC (HTPC), the one biggest problem is how to balance performance and heat. Since heat needs to be exhausted away from the computer, and the primary way to do that is with fans, it would stand to reason that the higher performing a component you want to install the noisier it’ll be. The two components that have the most effect on this are the video card and CPU. With video processing duties specific to home theatre and multimedia applications moving onto the motherboard we’re basically left with the CPU.
AMD has an answer to this conundrum; their latest low power processors offers all the performance of a Phenom II X4 at a reasonable clock speed and low-as-can-be TDP output.
Introducing the AMD Phenom II X4 905e Energy Efficient Quad Core CPU
The AMD Phenom II X4 905e is a processor designed specifically to provide the lowest CPU voltage while maintaining a decent clock speed. The CPU has four cores all clocked at 2.5GHz, while only running at a TDP (Thermal Design power) of 65W. The 905e basically contains the same core we’ve seen in the previous AMD Phenom II Black Edition processors we’ve reviewed, but the multiplier on this CPU has been locked to 12.5 (12.5 x 200MHz = 2500MHz = 2.5GHz).
In addition to the lower TDP, to further combat heat and improve stability the core voltage on this CPU has been reduced to 1.15V. This is indeed a purpose built part, as it can’t really be overclocked easily, and is tested to specifically run within the afore mentioned specifications.
Unfortunately the Phenom II X4 905e is priced like a purpose built part. The street price for this processor appears to be between $180 and $200 USD, depending on while vendor you go with. To put that in perspective, you can get a Phenom II X4 955 for about the same price, or a 965 for another $50. Making your decision easier is the fact that those processors spew a lot of heat due to their TDP ratings and voltage requirements. Also this is the cheapest CPU in this performance bracket, with the equivalent Intel Core 2 Quad running you another $60 to $80 USD. Seems like an easy choice to me. We just need to figure out how well it performs.
The Test Rig, aka My Home Theatre PC
I figured the best way to test the AMD Phenom II X4 905e was to install it in my current Home Theatre PC. This is pretty well what this CPU was built for; well thisa silent PC, but the goals of the two systems are essentially the same.
Here are the specifications for my system:
- AMD Phenom 9600 Black Edition CPU
- GIGABYTE GA-MA770-UD3 AM2+ AMD770 Mobo
- OCZ Platinum XTC REV.2 PC2-6400 2GB Dual Channel Kit
- Foxconn 9500GT-256FR3 OC Video Card
- Western Digital Caviar Black WD1001FALS 1TB Hard Drive
- Seagate Barracuda 7200.11 1.5TB Hard Drive
- Corsair HX520W Modular 520W Power Supply
- Arctic Cooling Freezer 64 Pro CPU Cooler
- Silverstone Grandia GD01-MX HTPC Case
This is actually my favourite system build. Unlike my performance rigs, which consist of throwing the fastest components together, this HTPC has parts that were selected specifically for the duties of an HTPC. The fans are all extremely quiet, and there’s a sound card installed to replace the awful onboard audio.
As for how I plan to test the CPU in this rig, I’m going to focus on some of the points I’ve made thus far. To see how this CPU stacks up against the 95W Phenom 9600 in there now, I’m going to test thermals and power consumption. I’m then to going to check CPU and multimedia performance, and see how quickly it chews through a compressing a DVD. Finally we’ll see if there’s any difference in CPU usage when playing back 1080p high definition video, testing to efficiency of each CPU.
A Twin Peak at the Two Procs
Comparing the older Phenom and newer Phenom II X4 processors side by side in CPU-Z, we get to see some of the differences that lay the groundwork for the benchmarks ahead. This may be a bit of a rehash for those who read our AMD Platform Showdown, but bear with me.
First and foremost is the 200MHz jump in speed when switching from the older CPU to the newer Phenom II X4 905e. This will help out in the few performance benchmarks we are going to do. As for the first tests we set out to do, the lower die size and lower voltage should help out. Multimedia testing should also see a bit of a boost from a more efficient core.
Heat and Power
The first test in our battery of efficiency benchmarks is a simple run through with OCCT. This program can monitor and log CPU and chipset temperatures, as well as voltages. We basically used it to drive the AMD Phenom II X4 905e to 100% CPU usage, gauging how much of a difference in temperature the lower voltage and smaller core make.
Idle temperatures weren’t that different, with only a 12% difference between the older core and our review unit. Placing load on the two processors made things a little more interesting. The 905e was 17% cooler under load then the older CPU, which is a good thing. The less heat the CPU dumps into the case, the better off your system will be in both stability and longevity.
Another area where the 905e is said to be ahead of the rest is in power consumption. To test this we used an UPM Blue Planet EM100 Energy Meter to monitor how many Watts the system was using, while running through a loop of 3DMark Vantage on Performance mode. We took our idle readings after letting the system sit for 30 minutes, which allows Windows Vista to settle down and stop doing things.
We found that at idle there wasn’t a significant difference between the processors, most likely due to the other hardware in the system. When we turned the dial up on performance the 905e did shine through, posting a 17% drop in power consumption while still posting a higher final score in 3DMark.
A Little Multi In Our Media
Our final test, before moving on to some performance benchmarks, is to simply see how the 905e handles HD playback when compared to the older CPU used in my HTPC. We tested CPU usage while playing back a 1080p h.264 video file of the Top Gear Polar Special. Of particular interest was the first couple minutes, as they are panning over a field of white snow with snow blowing over the surface. This scene has crushed most CPUs that aren’t quad core.
I’m happy to say that for a processor that only has an 8% boost in raw MHz, the Phenom II X4 905e used 19% less CPU resources playing back this video.
You Must Perform
Before wrapping this up, we need to do a couple performance benchmarks to show that the Phenom II X4 905e does actually post significantly better performance number then the older CPU. No it can’t all be efficiency tests. Anyhow our first benchmark consists of a run through PCMark Vantage. For this benchmark you’ll notice that we’ve nearly picked the exact same scripts as our regular CPU reviews, adding Music to play to the HTPC theme.
Overall the 905e posted an 18% performance boost in PCMark, but the breakdown of the scores is much more interesting. Productivity got the biggest boost, with the 905e posting a whopping 22% advantage over the older core. In direct contrast to our CPU usage test on the previous page, the TV & Movies benchmark was only 8% in the 905e favour. This scales perfectly only with the speed increase between the two processors, and doesn’t give any benefit to efficiency upgrades.
Music had similar results with only a 10% performance increase. This isn’t necessarily a bad thing, as these two benchmarks rate performance in editing, converting, and playback of their representative mediums.
With those numbers in mind, I decided the final benchmark we could perform that would most appropriate with the HTPC theme is to see how long it would take for the 905e to re-encode and compress a DVD into a more manageable format. Our format of choice was video optimized for the iPod. This was selected due to the limitations in Nero Recode, one of the few multithreaded video encoding programs that actually uses the full resources of the CPU.
The 905e blew away it’s previous PCMark Vantage number in this area, posting a 21% advantage on the Phenom 9600. This was with full 2-pass encoding enabled, and compressing a DVD copy of Stargate to CD size.
Final Thoughts and Conclusion
So what are we looking at after the dust is settled? On the one hand, the AMD Phenom II X4 905e seems like the perfect CPU for a home theatre PC or silent PC. It’s just as efficient as it’s 3GHz+ cousins, while running cooler and on less energy. This makes it more efficient than the original Phenom 9600 CPU I was using in my HTPC at the time of testing, but I think that was a given for the get go. The one thorn in the side of this processor is the price however the AMD Phenom/Phenom II platform itself provides value as any AM3 processor will drop in and upgrade your system on the spot without changing your motherboard and RAM. If AMD can make a chip this efficient, only time will tell what else they come up with as a drop in upgrade for AMD fans out there.
When one looks at the raw numbers, this CPU looks like it’s a bit too expensive. 2.5GHz processors are easy to come by and relatively cheap. The 905e requires explanation as to why it may be worth the dollar value placed on it. Requiring explanations like these tend to place products in a niche, which is where this CPU is headed. In looking around for a place that sells this CPU, I found Newegg had it deactivated. I only found a couple Canadian retailers who still had the 905e listed and in stock.
In the end, the AMD Phenom II X4 905e is a good product for a particular user. Earlier on I extolled the virtues of my HTPC, and why it was my favourite system build. Its purpose built, and it serves its purpose well. This CPU is the same way. It’s not the fastest in raw performance at its price point, but the intangibles are there waiting to be utilized. And hey, it’s still cheaper than the Intel part sporting the exact same specifications.
I would say that this is a recommended CPU for those looking to build a powerful HTPC or silent PC that strikes the perfect balance between cool, quiet operation and raw performance.
Pros
- Low TDP keeps temps down
- Reduced voltage prolongs CPU life
- Chews through video and audio
- Helps HTPC and Silent PC systems stay quiet
Cons
- Price to performance ratio a little out of whack
- Niche product, might be hard to come by
Overall Rating: 8.0/10.0
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