The Core 2 Quad Q8400: Intel's $183 Phenom II 940 Competitor
by Anand Lal Shimpi on May 7, 2009 12:00 AM EST- Posted in
- CPUs
Final Words
It took dual-core chips falling below $200 to start increasing their prevalence in the market, and today only one of our standard CPU tests won't see a performance increase from a dual core chip. I believe we're at the beginning of that same transition for quad-core CPUs. Many of our tests show a benefit from having four cores over two but in the next two years that should change significantly. The advent of GPU computing and the impending release of Larrabee will both bring about more focus on multi-threaded development. In the coming years a new group of applications that can run on both GPUs and multi-core CPUs will cement the transistion from applications that struggle to stress more than two cores to applications that scale to a virutally infinite number of cores.
The sheer affordability of quad-core processors today is impressive; $180 - $190 will buy you a Core 2 Quad Q8400 (2.66GHz/4MB L2), a Core 2 Duo E8500 (3.16GHz/6MB L2) or a Phenom II X4 940 (3.0GHz). Whether you go dual or quad is really a personal choice depending on the types of apps you run. If you look at our SYSMark 2007 results you’ll see that the E8500 is a better choice overall. Personally I’d opt for the quad core but that’s because when I’m most performance constrained it’s in applications that scale well to four cores, but if you don't do any 3D rendering or video encoding (or heavy multitasking between two multithreaded apps) then a fast dual-core may make the most sense for you today. If you're buying for a system that you plan on keeping for 3 - 5 years however, I suspect that quad-core is the way to go.
Between the Q8400 and the Phenom II X4 940, at stock clock speeds, the 940 is the way to go unless you're very concerned about power consumption or happen to be running applications that are very well optimized for Intel's Core architecture. Update #2: Intel has just confirmed that the Core 2 Quad Q8400 does support Intel's VT-x from the start, so the update below is incorrect. The Q8300, E5400, E5300, E7500 and E7400 will also end up transitioning to versions with VT-x support as well but only the Q8400 supports it from launch. Update: As many readers have pointed out, the Q8400 does not support Intel's VT for hardware accelerated virtualization. Honestly it's silly that Intel is attempting to use VT as a profit driver at this point. Not supporting VT on any quad-core CPU just doesn't make sense. The Phenom does support AMD's hardware virtualization AMD-V, and thus gives it a tremendous leg up if you care about the feature.
If you plan on doing some light overclocking, the Q8400 has more inherent potential. Start bumping up core voltages and the Phenom II X4 940 regains strength as it's able to increase the clock speed advantage once more. Throw overclocking into the mix and the comparison isn't quite as clean cut, both AMD and Intel trade blows in their advantages. I'd say AMD would probably have more wins in our applications but at the expense of much greater power consumption.
It's good to see that there's competition here, but Intel's profit margin advantage on the Q8400 is ridiculous. AMD has to sell something Nehalem sized for under $200 to remain relevant today. I'm far less concerned about who pulls ahead while overclocked and far more concerned about AMD's health at the end of all of this. Maybe the right way of looking at this isn't by talking about a 6% performance advantage, but instead talking about whether or not you want there to be a real competitor to Intel in the future. Maybe the Phenom II X4 940 should get the win here just to ensure we have an AMD to talk about in a couple of years...
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TA152H - Friday, May 8, 2009 - link
Anand,Have you ever asked Intel why they don't lower the latency of their processors when they cut the cache size? Why should a processor with two MB cache run at the same latency as one with six MB? Certainly it does not need to.
I could understand it where they are just cutting off some of the cache because it's faulty, but when they are actually two different dies, with the different cache sizes designed into the chip, why do they artificially slow down the chips with the smaller cache? They should have no trouble lopping off one cycle, since the 4 MB Conroes were 14 instead of 15, and these processors are 2 MB cache per core, so it could allow 13 cycles, but surely can handle 14 easily.
It's maddening when Intel slows things down for no good reason. It's probably a marketing decision, and we all know how marketing decisions are.
Anand Lal Shimpi - Friday, May 8, 2009 - link
It actually comes down to design resources. It's fairly easy to change a cache size, but changing the access latency requires more of a design change. I'm guessing those resources are better spent on newer architectures. e.g. Intel could go back and make even better versions of the Penryn based cores, but it makes more sense to put those efforts into engineering Westmere and its successors.Plus, a given architecture is usually optimized for whatever latency cache it's originally designed with. Speeding up the L2 may not yield as big of a gain as it would had the architecture been originally designed around a faster L2.
I believe there's always a focus on lowering cache latencies, and that's what we saw with Nehalem. From what I've heard, the new focus is bringing down that L3 latency...
Take care,
Anand
Seramics - Friday, May 8, 2009 - link
I noticed a strange trend in Phenom II X3 720 performance. They consistently performed very well, always outperforming similarly clocked buy quad core model of PII X4 920 and sometimes even besting PII X4 940. Strange... wonder why is that... the only advantage of 720 over quad models is higher L3 cache per core... but still, i would thought even 920 should be better.... strange strangecfaalm - Friday, May 8, 2009 - link
Why are we getting new Core2 models in the first place? Shouldn't Intel be selling us i5 rather sooner than later?garydale - Friday, May 8, 2009 - link
In almost every benchmark the AMD chip bested the (cheaper) Intel - often by a noticeable margin. The real competition for the 940 remains the 9400. A better comparison would have been between the 8400 and one of AMD's comparably-priced CPUs.Still, with VT disabled on the 8400, we're talking apples and oranges. I don't know what Intel were thinking by disabling it but seems remarkably silly with virtualisation even hitting home users these days. It's quite like disabling SSE but the idea seems like a win for marketing over engineering. Pay the extra $30 and get a CPU.
ssj4Gogeta - Saturday, May 9, 2009 - link
I can't understand what all this fuss is about. As if everyone in the world is going to be running the Ultimate version of Windows.LoneWolf15 - Friday, May 8, 2009 - link
Intel VT as well.Sorry, I think my Q6600 is worth more than a Q8400 for that reason alone. I'm also pretty sure that AMD's hardware virtualization trickles down to a cheaper level than Intel's does.
Intel really needs to stop cutting VT on all but perhaps Celeron-class CPU's and maybe Pentium Dual-Core on laptops. I certainly wouldn't buy anybody's quad-core that didn't have it.
leexgx - Friday, May 8, 2009 - link
all AM2 or higher chips have amd-V (apart from semprons None of them have amd-V), i think some 939 cpus have amd-V not sure but not the point realy as thay not been sold for yearsall q8000 cpus do not have VT (unless thay bring one out that does), q9000 do
Scali - Friday, May 8, 2009 - link
Yup, AMD leaves VT enabled on pretty much everything.Makes sense, because it's an added value over Intel's offerings, and it doesn't cost much extra, since it's already in the chip design.
For Intel it makes sense to leave it disabled, because it's a feature that's mainly useful for business users, and Intel has always tried to push business users to the high-end CPUs by disabling certain features on the lower-end models. Performance alone isn't really a reason to get a high-end CPU anymore.
LoneWolf15 - Friday, May 8, 2009 - link
It will be useful for far more than business users shortly. Windows 7's new XP-mode option requires Intel VT or AMD-V. While I admit that so far I haven't had app issues under Win7RC (that includes 32-bit app issues in a 64-bit environment) there IS one 16-bit app I still run that I'm sure I'll need XP mode for under 64-bit Windows. I'm also sure there will be other instances that pertain to the general market.Eventually, hypervisors are going to be a big deal, just like multi-core processors are becoming now. At that point, people without Intel VT will be screwed, and I think they'll be pretty ticked if they're the ones that thought that buying a quad-core CPU like the Q8400 was a good future-proofing move.