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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agaelebe - Friday, March 2, 2007 - link
Wow! A lot of dicussion in here.And, by the way, very interesting article.
I'm a software engineer from Brazil and I'm planning to change my PC this year.
I've bem using AMD processors since the K6.
Today I've a XP Mobile 2500+(@2.2ghz), 1gb ram, 200gb and an AGP 6600GT
My PC is not very slow, but I'm thinking in going dual core to speed things up(office applications, web development and some games).
I can run some of the newest games, but not in high graphics.
I expect that my PC can run C&C 3 (Already run the demo in 1024 medium, but have some craches although it's not running it slow)
So, today I'm thinking in 3 options:
1) Stay with this computer and wait until AMD launchs it's new architecture (I pretend to go with an average price Kuma)
2) Go with Intel Core 2 Duo (e6300 or e6400). They're not expensive and for games I can easily make an overclock and gain more performance.
3) Buy a good AM2 board and a cheap Atlhon X2 (3600) and wait new AMD processors and then change only the processor.
Here in Brazil the taxes are to high, so I'm planning in buying a PC with these specs:
- CORE 2 Duo e6300/6400 or X2 3600/3800
- mid-tier motherboard (
- 2 x 1gb DDR 800 4-4-4-12
- 2 x 250 gb
- X1950pro 256 or 512
- 500watts power
So the prices are below:
e6300 box US$ 300 (same price for a X2 4200+ box)
x23800 box US$ 220
motherboard: US$ 220
ram: US$ 400
video: US$ 450
DVD: US$ 70
case: US$ 150
HDs : US$ 250
Power: us$ 180
So I plan to spent about 2000 dollars (Sadly, I can buy this same PC in US for the half of the price).
My new PC should spent not to much power so I can leave it turned onall day long(max 150watts on iddle without monitor), otherwise I'll keep my old computer turned on just for downloding stuff)
So, If someone has an opinion, I'd like to "hear" it. You can give another options to, or make some comments about the specs I'm choosing now.
I had Pentium 75 and after that only AMD CPUs... Should know I surrender to the Core 2 Duo or believe that AMD can really beat it until the end of 2008?
And thanks for the cooperation and patience.
Zebo - Saturday, March 3, 2007 - link
Athlon 64 AM2's arnt exactly slow so if you're an AMD fan just get one..like a 3800+ or 3600+ and overclock it. It will be at least 4x faster than what you have now and accept K8L Agena core later. It will be cheaper than C2D by about $50 USD and You'll also pay cheap for a GeForce 6100 Motherboard which is only $50 USD. Overall expect the the AM2 system to be about $100 USD cheaper.Keep in mind that C2D is 20% faster clock for clock in most apps so it's not exactly a quantum leap here getting a C2D.. Gap gets a lot larger when overclocking since C2D's overclcok higher like 3.2Ghz is common on air vs. only 2.8Ghz for AM2, so, at the end of the day a C2D setup is able to be about 40% faster over most benchmarks. That is getting significant and why enthusiasts are buying C2D's.
agaelebe - Friday, March 2, 2007 - link
And,as always, sorry with the errors and not so good writing...Kiijibari - Thursday, March 1, 2007 - link
Hi,never heard of of that before, does anybody know what it is ?
So far I see 2 pad areas at the DIE photo, therefore I assume that it would be also 2 interfaces, e.g. x8 PCIe like Sun uses ?
bb
Kiijibari
mino - Friday, March 2, 2007 - link
It should be some management/coodrination stuff (can-t remember the name of that bus).Every northbridge and CPU has that.
davecason - Thursday, March 1, 2007 - link
Anand,Great article! I know it took a lot of time and I wanted you to know I really appreciate your effort. It is the kind of article that keeps me coming back to your site.
-Dave
yyrkoon - Thursday, March 1, 2007 - link
Page 5, paragraph 4 'pretty significantly'. Well is it, or is it not it ?
http://www.wikihow.com/Avoid-Colloquial-%28Informa...">http://www.wikihow.com/Avoid-Colloquial-%28Informa...
Aside from my gripe concerning writing style, good article :)
trisweb2 - Friday, March 16, 2007 - link
Usually we criticize writing style based on a whole experience... obviously Anand is one of the best technical review writers on the Internet; if you bother to read his articles more fully perhaps you'd realize that. The colloquial writing sometimes brings it to a more personal level that a reader can better relate to and understand -- it works especially well in this case, where it's a future design, we really don't know how it's going to perform. That he can guess and say "pretty significantly" tells me he understands the uncertainty of the situation, and the language communicates that fact perfectly well. It would be more confusing if he said it would impact performance "significantly" as you want him to, as that would imply that he was more certain than he might actually have been.Masters are allowed to bend the rules, and Anand is one, so lay off.
yyrkoon - Thursday, March 1, 2007 - link
*Is it, or is it not*/me hangs head in shame
baronzemo78 - Thursday, March 1, 2007 - link
Any rough guess as to how Barcelona will compete with Core2 in gaming? Many articles have shown how Core2 gets you a slight FPS boost in games that aren't graphics card limited. I'm curious how Barcelona will fit in with the overall picture of DX10 cards like G80 and R600.