UK EXCLUSIVE: Barcelona benchmarked

 

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Posted on 3 Oct 2007 at 10:41

After what seems like forever (actually a delay of just over six months), we've finally got our hands on production samples of AMD's Barcelona quad-core CPUs.

Barcelona - Quad-core Opteron, to give its production name - is the first Opteron to use 65nm fabrication, down from the 90nm of its previous-generation processors. Being Opterons, the new parts are bound for servers and workstations. Phenom, the consumer version based on the same architecture and replacing the Athlon range, will be coming next year.

Besides supporting four processing cores on a single silicon die, the major architectural difference is in the cache arrangement, being the first processor in modern times to sport L3 cache. While each core has 512KB of dedicated L2 cache, the third level is a shared extra 2MB available to all four cores for a total complement of 4MB.

Investment protection

Putting AMD's constant claims of investment protection to the test, we were keen to upgrade an Opteron NEC WA2510 workstation from its twin dual-core Opterons up to a pair of our test 1.8GHz 2346HE quad-core Barcelona parts, making for an eight-core workstation. AMD has made much of the fact that the new processors protect investment by being physically and thermally compatible with older second-generation Socket F CPUs, claiming on numerous occasions that existing systems would be upgradable to the new parts with nothing more than a BIOS update.

That may be true in the majority of cases, but certainly not all of them: the Tyan S2927 board in our three-month-old workstation doesn't support the dual-power planes of Barcelona. The message here is not to make any assumptions and only consider switching out the CPUs in existing systems if you have a specific compatibility assurance for the motherboard model you own. So, unable to use the WA2510, Boston supplied us with an impressive Barcelona-compatible rack-server system for testing, which we review in full here.

The numbers game

In terms of raw performance, Barcelona delivers no great surprises. To compare it core-for-core with the previous generation, we installed two dual-core Opteron 2214 CPUs in the Boston server, benchmarked and power-tested the system, and then replaced the two dual-core chips with just one of our test quad-core 2346HE parts.

From the results, it seems that the new L3 cache isn't doing Barcelona's architecture many favours; the single quad-core Barcelona system came out slower in every test than the dual, dual-core setup, including our multiple applications and multithreaded 3D tests. The clock-speed differential (1.8GHz against 2.2GHz) as well as the fact that a dual-CPU setup has its own dedicated banks of memory are both factors in the old Opteron's favour, of course, but we'd have hoped the new architecture would have closed the gap to a greater extent.

When it comes to performance per watt, the story continues to be interesting and far from clear cut. The 95W TDP (thermal design power) of the dual-core 2214 looks very hefty in comparison to the 55W ACP (average power consumption, a new figure that AMD believes reflects real-world usage more accurately than TDP) of the 2346HE, and when you look at consumption per core it's even clearer: 47.5W per core for the old part, compared to a mere 13.75W per core for the new.

Monitoring power consumption during our 3ds max test render - an extremely efficient user of all available cores - we were able to derive a performance-per-watt factor from average power consumption in relation to the time taken to render the first frame.