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.
Facebook
Twitter
RSS
83 Comments
View All Comments
JarredWalton - Thursday, March 1, 2007 - link
Games have quite a lot of LOAD instructions, like most programs, as well as plenty of branches (esp. in the AI routines). Most likely the boost that Core 2 gets is due in a large part to the better instruction reordering and branch prediction, although the cache and prefetchers probably help as well. Given AMD was better than NetBurst due to memory latency, through in better OOE (Out of Order Execution) logic and keep the improved latency and they should do pretty well.Naturally, everything at this point is purely speculation, but in the next few months we should start to get a better idea of what's in store and how it will perform. One problem that still remains is that even if AMD can be competitive clock-for-clock, Intel looks primed to be able to go up to at least 3.6 GHz dual core and 3.46 GHz quad core if necessary. AMD has traditionally not reached clock speeds nearly as high as Intel, possibly due in part to having more metal layers (speculation again - process tech and other features naturally play a role), so if they release 2.9GHz Barcelona at $1000 you can pretty much guarantee Intel will launch 3.2 and/or 3.46 GHz Kentsfield (and/or FSB1333 3.33 GHz).
On the bright side, at least things should stay interesting in the CPU world. :D
yyrkoon - Thursday, March 1, 2007 - link
Yes, interresting indeed, but from experience, AMD has always been too vocal in what they plan on doing, especially during the times they are in a 'rut'.What this usually means to me, is that AMD is trying to blow smoke up our backsides, we'll see though.
Keep in mind, my main desktop system, and my backup server for that matter, both are AMD systems. The phrase "cost effective" applies here.
kilkennycat - Thursday, March 1, 2007 - link
Yesterday, Intel announced that they were converting a fourth fab to 45nm. A great deal of confidence in that process. And a few days ago they announced desktop shipments of Penryn-based CPUs pulled forward into 2007. Looks as if AMDs 'window of opportunity' is likely to be very small. IBM has not yet announced a successful implementation of a RAM on their 45nm process. Intel had their RAM design on 45nm up and running late 2005.archcommus - Thursday, March 1, 2007 - link
True but the move to 45 nm might not make a huge difference in real world performance, just like the move to 65 nm didn't for AMD. Their next full blown architecture will still be a ways off.Roy2001 - Thursday, March 1, 2007 - link
Dislike AMD's move to 65nm process, move to 45nm has shown that Penryn would eats less power and runs faster thanks to its high K material and metal gate.smitty3268 - Thursday, March 1, 2007 - link
Every process shows that in theory before chips are actually being made on it. We'll see what actually happens when Penryn is released, not before.chucky2 - Thursday, March 1, 2007 - link
Has AMD given any indication of how probable dropping an Agena or Kuma CPU into an existing AM2 motherboard will go?Especially AMD's own newly released 690G or the upcoming nVidia MCP68?
Chuck
mamisano - Thursday, March 1, 2007 - link
It has been stated in the past that AM2+ based products will run in AM2 based boards. The limitation, if I understand it correctly, will be the lack of support of the new power features.Someone correct me if I am wrong :)
chucky2 - Thursday, March 1, 2007 - link
Then it should be no problem for AMD to confirm through AnandTech that this is the case.Surely if Barcelona is this close to shipping (only a few months away), AMD must know if Agena and/or Kuma will work in current AM2 motherboards, especially their own 690 series their just about to release.
All I'm asking for is a definite either way, it shouldn't be that hard for AMD to do at this point.
Chuck
mino - Friday, March 2, 2007 - link
AMD stated PUBLICLY to anyone who listened that AM2+ stuff will plug into AM2, just BIOS update needed.Why should they react to any consumer who ask on some forum the same question every second week ?
Most important is they said it WILL(not "may") work with AM2-spec boards to big Tier 1 OEM's.
They can not make it incompatible therefore. They would be out of bussines in no time.