Daily News (Tech) Overclocking the Phenom 8750 Triple-Core

[Guy00]

It was almost The Overclock That Wasn't.

After a long and mostly fruitless battle, I must conclude that the Phenom 8750 Triple-Core was manufactured with extremely little overhead. Oh yeah, I fought it. I raged through the BIOS, specifically Gigabyte's MB Intelligent Tweaker (M.I.T.) page. I went easy at first, as every overclocker should do. But every time I tried to really push the envelope, the CPU pushed back. Three cores of didn't-want-to-budge fury in my face, I finally gave up.

It took about two entire, 10 hour days, and a few hours in the middle of the night, too. I battled across the memory frequency, the CPU voltage, and, of course, what passes for the FSB on an AMD-based system. Because the chip is multiplier-locked, any gains would have to be made there. Gains, however, were a precious few hundred megahertz and even those were hard to come by.


Read on for the blow-by-blow account of the glorious battle. A battle that the Phenom 8750 won, and I—and users who wish to overclock this CPU—lost. Continued... About a week or so ago, I reviewed the AMD Phenom 8750 Triple-Core CPU at spec. I pitted it against an Intel Core 2 Duo E8400, which runs at about the same price, and, surprisingly, the Phenom held its own. That's the first time I've been happy with the performance of an AMD processor in a very long time.

I promised in that review to give the Triple-Core CPU a good thrashing in overclocking tests. Here are the results. They're disappointing, but not altogether unexpected considering my last overclocking-centric encounter with an AMD Phenom CPU.

The testbed is the exact configuration I used in the review of this Phenom 8750, and it's based around a Gigabyte GA-MA78GM-S2H motherboard powered by the AMD 780G chipset. Gigabyte has made a name for itself in terms of overclocking with its M.I.T. technology, which gives the user excellent BIOS-level control over the chipset and the CPU.

Specifications are:

Component Make/Model

Processor Phenom 8750 Triple-Core

Motherboard and chipset Gigabyte GA-MA78GM-S2H / AMD 790G

Memory 2GB Corsair DDR2 CM2X1024-10000C5D

Hard drive Seagate ST3320620AS SATA-II 7200.10 320GB

CPU Cooler Arctic Cooling Freezer 64 Pro

Frequency 2.4GHz

Socket AM2+

Audio SoundBlaster XtremeGamer

Graphics AMD/ATI Radeon HD 3870 X2

Operating system Windows Vista Home Premium SP1


Note the CPU cooler: the excellent Freezer 64 Pro. This, coupled with just enough Arctic Silver 5 thermal compound, ensured the CPU never got very hot. In fact, in a Prime95 torture test with all three cores being punished, the CPU temp never cleared 60 degrees Celsius. It idled at about 33C.

Nevertheless, when I really tried to turn the screws on the overclock, Windows Vista coughed up one BSOD after another. At one point, I had to restore a cloned image of the freshly formatted and installed Vista partition because the installation became unloadable. It went into a continuous boot-BSOD-reboot cycle.

I used the methodology outlined last year, which is a solid technique for overclocking pretty much anything. I raised the system frequency slightly, and later tweaked the memory settings a bit to maintain the HT frequency as near as 1800MHz as possible. No matter; by the time I pushed the system clock past 225MHz (its native is 200MHz, and the CPU multiplier is locked at 12x for a native frequency of 2.4GHz), the dreaded bluescreen reared its ugly head. Continued... An overclock of a mere 25MHz on the FSB, with a 12x multiplier, comes out to only 2.7GHz, a gain of 300MHz, or about 12.5%. That's really not much to get excited about. Every time I tried to go beyond that, though, the system either wouldn't boot at all, or it would BSOD within seconds of the Vista desktop appearing.

I attempted to alleviate the situation by raising the core CPU voltage, easing it above its factory max of 1.25V. That had no effect. I tried to go easier on the memory by lowering the spec through the BIOS; it didn't help. I checked the CPU temperature frequency to see if it was overheating, but it rarely got above 40C at idle.

This chip wouldn't budge past about 2.7GHz, and that was that. Anything even higher caused unacceptable instability.


Unfortunately, such a minor overclock resulted in barely-noticeable performance improvements. Most of the noted performance enhancements barely showed up in synthetic benchmarks, and real-world gaming was only marginally affected. Nevertheless, we did run a series of performance tests. Continued... We tested pre- and post-overclocking. We'd planned on running a series of tests as we pushed the CPU higher and higher, but since the first stop at a 300MHz gain was the last, there are only two sets of data to contend with.

The performance tests we used were:


PCMark Vantage: The latest, Vista-required full-system benchmark from Futuremark. It blasts the entire PC and each subsystem and comes back with a series of scores for various functionalities.


3DMark Vantage: The DirectX 10 synthetic GPU benchmark from Futuremark. It pits the graphics subsystem and the CPU against a series of game-like routines, plus a number of direct feature tests.


3DMark06: The DirectX 9 synthetic from Futuremark. This benchmark assesses the GPU and CPU with a series of gamecentric environments.


Crysis: The ultimate real-world game benchmark is brought to you by the most realistic looking game there is. Capable of both DirectX 10 and DirectX 9 graphics, it's the killer app in more ways than one.


World in Conflict: A powerful RTS with astronomical graphics, this DX9 and DX10 hybrid game boasts a tough benchmark.


Company of Heroes: The original RTS-that-thinks-it's-an-FPS, this DX 9 game later added some DX10 effects just to become even more realistic than it already was.


Supreme Commander: The giant-robot RTS, this game boasts some of the harshest DirectX 9 graphics, plus CPU-brutal physics calculations running the entire way through.


The machine was fitted with the latest drivers for all of its components as of June 25, 2008, including AMD/ATI's Catalyst 8.6 suite for the graphics card. Continued... The gains were hardly statistically significant, but they were somewhat consistent throughout the synthetic benchmarks. First up: PCMark Vantage.


The results almost mirror each other, with little performance gain seen from the 300MHz boost—mainly in the overall score and the Productivity score.


In 3DMark Vantage, there was almost no difference from one score to the next.


The same goes for legacy, synthetic benchmarking. Continued... Meanwhile, in gaming, we don't see huge gains either.


Besides Supreme Commander, the Crysis CPU benchmark shows the most performance difference between the spec and overclocked system. Still, the gains are minimal.

Depending more on the graphics card than the CPU, the Crysis GPU benchmark was fairly static.


Both World in Conflict and Company of Heroes showed only modest gains, if any at all.


Supreme Commander, perhaps being more CPU dependent than the other games, did show some significant improvement. One out of four ain't bad, right? Well, it isn't very good. Continued... The battle was finally over. I threw up my white flag, once again a victim of a Phenom CPU with very little factory overspec to speak of.

I'd tried everything to win. I tried the direct assault, by attacking the system frequency. I tried flanking maneuvers, by tweaking memory and HT settings. I sent in the spy, by upping the CPU core voltage. The enemy was ready for my every move, and countered with its dreaded and always-devastating Blue Screen defense.

I was helpless, with no other option than to concede this battle. I'd fought hard, and rather than go down fighting, I chose the better part of valor: To live to fight another day (and to avoid frying another installation of Windows Vista).

In my concession speech, I noted the Phenom 8750's "lack of overhead" and "tight manufacturing." But I also left the door open: Not every Phenom I encounter will defeat me. I shall prevail...one day.

When are those 45nm Phenoms shipping?