Intel vs. AMD 6-core CPUs: Speed vs. power?

Opinion – When Intel introduced its Dunnington 6-core processors back in September of 2008, we considered it a stunning achievement, but knew that it would be about as far as the Core architecture would allow Intel to go. Today’s announcement of the Istanbul CPU shows that AMD is catching up, at least in some product segments.

Let’s get this straight from the start. Like most of us geeks, I am still impressed how Intel has recovered from the Netburst architecture dilemma of the early- to mid-2000s, the way how Core has turned out and what Nehalem brings to the table. At the same time I was wondering when AMD would be able to challenge Intel again, after the Barcelona quad-core CPU disaster and a Shanghai processor that got much less traction than some thought. The new Istanbul 2400/8400 series appears to be such a chip that brings AMD back to the table.   

My optimism is based not so much on the speed of the Istanbul processors, but on the balance the chip offers, at least from what is possible to see to spec sheets and published benchmarks. There are very few published benchmark results of 6-core Opteron processors – in fact, the maximum SPECint_rate2006 value of 205 for the 2435 model (2.6 GHz, two CPUs, 8×4 GB) and 402 for an 8435 platform (2.6 GHz, four CPUs, 16×4 GB) are the only relevant results publicly available at this time. The integer value is about on par with a comparable Intel quad-core X7350 Tigerton CPU (211) system (16×2 GB). AMD will have to admit that, in terms of pure performance, Istanbul gets smoked at this time. A 2.66 GHz X7460 Dunnington system turned in a value of 291. And the performance gap is even more obvious if we are looking at the recently launched Nehalem-based Xeon 5500 series. A W5580 chip is posted with a performance level of 260.

However, Istanbul’s value is not just in performance, it is in power consumption. The chip is rated at a thermal design power of 75 watts, while the X7460, X7350 and W5580 carry a 130 watt rating (The X7460 can actually run up to 170 watts, according to Intel’s published tech documents.) I don’t want to get in the midst of a power efficiency discussion, but it is obvious that if performance isn’t everything, AMD clearly has a case with Istanbul. However, if companies consider 2-way servers and they do not need 4p and 8p configurations, it is an interesting side note that the quad-core Xeon E5520 processor is about comparable with AMD’s 2435 at a SPECint_rate2006 value of 199 and a TDP of 80 watts. At least in this perspective, it appears that Istanbul may be an interesting option for server buyers again.

Interestingly enough, it seems that AMD is aware of that circumstance and has priced its processors accordingly. I agree that a 6-core chip by default has to carry a certain premium over quad-cores, but the 2400 series may be a bit too expensive. The flagship 2435 clocks in at $989, which is less than any Intel 6-core (MP) chip, which start at $1177. However, it is substantially more expensive than a comparable 5500 series Xeon: The E5520 is priced at $373. The Opteron 8435, which compares directly to Intel’s 7400 series, runs for at least $2149 (8431, 2.4 GHz), which is just below Intel’s 2.4 GHz (90 watts) E7450.   
It’s good to see AMD back in the game, especially in the 4P and 8P segment. As it is always the case with these processors, the true performance and power efficiency is heavily dependent on the applications are running, but it seems that the new Opterons in fact carry much more business value than their quad-core predecessors.

Wolfgang Gruener is the founder of TG Daily. The opinions expressed in this commentary are solely those of the author.