Barcelona Architecture: AMD on the Counterattack
by Anand Lal Shimpi on March 1, 2007 12:05 AM EST- Posted in
- CPUs
The Chip
Barcelona is AMD's first quad-core processor, featuring four cores on a single 65nm die. Unlike Intel's quad-core Kentsfield, Barcelona is not made up of two dual core die, which is why AMD calls it a "native" quad core solution. Although there is a technical performance advantage to AMD's approach, we're unsure if it's something that will be visible in real world testing.
Built on AMD's 65nm process, Barcelona is a more complex design than the K8 requiring a total of 11 metal layers compared to 9 for K8 and 8 for Core 2. AMD has required more metal layers at the same process generation than Intel in previous years, so Barcelona is not unique. Additional metal layers make manufacturing a bit more complicated, but there are no significant downsides to the end user.
With four cores and an optional 2MB of L3 cache on-die, Barcelona weighs in at 463 million transistors. At 463 million transistors, Barcelona is 119 million transistors shy of Kentsfield's 582M count. The lower transistor count boils down to a lack of cache; each Barcelona core has a 128KB L1 cache and a 512KB L2 cache, with all four cores sharing a 2MB L3 cache, for a total of 4.5MB of cache on-die. Each of the two die that compose a single Kentsfield have two cores, each core with its own 64KB L1 and a shared 4MB L2. A single Kentsfield chip has a total of 8.25MB of cache on-die, over 80% more than Barcelona, thus explaining the 25.6% increase in transistor count.
However, Barcelona is far more than a quad-core K8 with an L3 cache. We estimate the number of non-cache transistors in a dual-core Athlon 64 X2 to be approximately 94M, and the Barcelona core is around 247M; even doubling the dual-core K8 figure won't get you close to Barcelona. Note that simply doubling the 94M number also isn't an accurate comparison as Barcelona only features a single on-die Northbridge. In essence, there are more than 60M additional transistors (or more than 15M per core) that went into architectural enhancements outside of more cores and cache in Barcelona.
Barcelona is AMD's first quad-core processor, featuring four cores on a single 65nm die. Unlike Intel's quad-core Kentsfield, Barcelona is not made up of two dual core die, which is why AMD calls it a "native" quad core solution. Although there is a technical performance advantage to AMD's approach, we're unsure if it's something that will be visible in real world testing.
Built on AMD's 65nm process, Barcelona is a more complex design than the K8 requiring a total of 11 metal layers compared to 9 for K8 and 8 for Core 2. AMD has required more metal layers at the same process generation than Intel in previous years, so Barcelona is not unique. Additional metal layers make manufacturing a bit more complicated, but there are no significant downsides to the end user.
With four cores and an optional 2MB of L3 cache on-die, Barcelona weighs in at 463 million transistors. At 463 million transistors, Barcelona is 119 million transistors shy of Kentsfield's 582M count. The lower transistor count boils down to a lack of cache; each Barcelona core has a 128KB L1 cache and a 512KB L2 cache, with all four cores sharing a 2MB L3 cache, for a total of 4.5MB of cache on-die. Each of the two die that compose a single Kentsfield have two cores, each core with its own 64KB L1 and a shared 4MB L2. A single Kentsfield chip has a total of 8.25MB of cache on-die, over 80% more than Barcelona, thus explaining the 25.6% increase in transistor count.
However, Barcelona is far more than a quad-core K8 with an L3 cache. We estimate the number of non-cache transistors in a dual-core Athlon 64 X2 to be approximately 94M, and the Barcelona core is around 247M; even doubling the dual-core K8 figure won't get you close to Barcelona. Note that simply doubling the 94M number also isn't an accurate comparison as Barcelona only features a single on-die Northbridge. In essence, there are more than 60M additional transistors (or more than 15M per core) that went into architectural enhancements outside of more cores and cache in Barcelona.
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Amiteriver - Tuesday, March 27, 2007 - link
Sounds groooovyNow lets just hope they have something good to plug it into.
trisweb2 - Friday, March 16, 2007 - link
I just want to say how refreshing it is to read an article written by Anand. He is a master of the English language; he perfectly communicates and explains every technical detail and I come away with a better understanding of whatever he's talking about.Thank you, Anand, for being a good writer!
MrWizard6600 - Thursday, March 22, 2007 - link
I Agree, Outstanding.No other site I know of gives nearly as many in depth details, and while ill admit my knowlage of some of the terms is sketchy, I got through that one with a good understanding.
Sounds like AMD has something to fight Core 2 against.
I do have one criticism:
I would have loved to have heard what Intels equivilent to all of AMDs technologies would be, mind you this criticism corrects it self toward the end of the artical.
stance - Monday, March 5, 2007 - link
Remember AMD's old president and CEO Jerry Sanders with commentslike "We will see what we see" and "More bang for your buck" I
cannot wait to see duel socket motherboards with two four core
Barcelona's working their magic. reminds me of Carol shelby
when he brought the Cobra out for road test. exciting is not
the word, jaw droping performance? Don't take Richard's Statements
lightly
lordsnow - Sunday, March 4, 2007 - link
Does anyone have any idea how compatible the "Barcelona" CPU will be with current motherboards? When it comes out, does it need a new n-phase voltage regulator, for example?the reason I'm asking is, I want to upgrade and with the current state of affairs was going to go for a C2D CPU. But with these Barcelona CPU's due out I may stick with AMD - get a AM2 motherboard and cheap AM2 CPU and upgrade to the Barcelona CPU at a later date. But I have to be sure that whatever motherboard I buy now will be 100% Barcelona compatible.
Can anyone inform us about what the situation is in this regard?
coldpower27 - Sunday, March 4, 2007 - link
Barcelona being the server variant will be compatible with the Socket F infrastructure, while Agena will be a Socket AM2+ processor compatible with exisiting Socket AM2 infrastructure.lordsnow - Sunday, March 4, 2007 - link
Any ideas as to what kind of features a user will be missing by dropping a AM2+ "Agena" CPU into a AM2 socket? The enhanced Power Saving features, perhaps?chucky2 - Sunday, March 4, 2007 - link
I asked above and non-AnandTech folks like you and I said it would...but no one from AnandTech themselves jumped right in to give an affirmative.I asked for links from AMD's own website confirming that Agena and Kuma would work in current AM2 motherboards, and no one posted back.
Right now the AM2+ CPU's will work in current AM2 boards rumor is just that, a rumor...when AMD themselves confirm it, or a site such as AnandTech confirms it with AMD and reports on it, then I'll believe it.
Until then, it's <i>probable</i> that AM2+ will work in current AM2 motherboards...if you're willing to take the risk I say go for it, else, wait until we have an official answer one way or the other.
JMHO...
Chuck
Calin - Saturday, March 3, 2007 - link
"Intel regained the undisputed performance crown it hadn't seen ever since the debut of AMD's Athlon 64."Intel in fact lost the "undisputed performance king" title during the early lifetime of the K7 architecture. The Pentium !!! was faster at some tasks and slower at others (games) than the K7. Before that, the Pentium II was better than the K6-2 (the K6-3 had better IPC than Pentium3, but was slower in MHz)
coldpower27 - Sunday, March 4, 2007 - link
Intel had the undisputed performance crown again with the Athlon XP 3200+ vs the Pentium 4 3.0C/3.2C and higher processors.