Intel Core Duo (Yonah) Performance Preview - Part II
by Anand Lal Shimpi on December 19, 2005 12:55 PM EST- Posted in
- CPUs
What about Clock Speeds?
Whereas the Pentium 4's extremely deep pipeline made clock-for-clock comparisons to the Athlon 64 virtually meaningless, the Pentium M and Yonah processors feature far shorter pipelines akin to AMD's architecture.
The Athlon 64 features a 12-stage integer pipeline, and while Intel has never specifically disclosed the length of Yonah's pipeline, they have made two important statements: it is longer than the Pentium III's 10-stage integer pipeline, and shorter than Conroe/Merom's 14-stage pipeline. Given the relatively tight range, Yonah's pipeline can pretty much be considered to be very similar to AMD's Athlon 64, give or take a stage of the pipeline.
The net result is that we can draw some valid conclusions based on comparisons of Yonah to the Athlon 64 X2 at similar clock speeds.
But our Yonah sample ran at 2.0GHz, which ends up being the speed of the slowest Athlon 64 X2 that is currently available: the 3800+. The highest end Athlon 64 X2s currently run at 2.4GHz, with high speeds just around the corner. So the question isn't just how competitive Yonah is at 2.0GHz, but rather, how high can Yonah go? Unfortunately, our test platform wouldn't allow us to overclock our chip very far, but thankfully, we have access to a decent amount of Intel's future roadmaps, so we can at least see what's going to happen to Yonah over the next year.
While Yonah will make its debut at a maximum speed of 2.16GHz, it will actually only receive a single speed bump before Merom's release at the end of the year. That means that we'll see a 2.33GHz Yonah after the middle of the year, but we'll have to turn to Merom to get any higher clock speeds.
Looking back to our initial articles on the Pentium M's architecture, you'll remember that one of the important aspects of its design is that all critical paths in the chip were slowed down to meet a maximum clock target. This means that Intel set a clock target for the CPU and made sure that the chip ran at that speed or below, and did not optimize any paths that would have allowed the CPU to run higher. Instead, the Pentium M team depended on the manufacturing folks to give them additional clock speed headroom by providing smaller manufacturing processes every 2 years. In other words, the Pentium M was never designed for high clock speeds, which is why it debuted at 1.5GHz and still has not even reached 2.33GHz today.
Intel's next-generation microarchitecture hopes to change that approach ever so slightly by introducing a longer pipeline into the equation, but on a much more conservative basis than the Pentium 4 did just 5 years ago. Conroe (desktop), Merom (mobile) and Woodcrest (server) will feature a 14-stage integer pipeline, which will allow for higher clock speeds than what Yonah could pull through. We would expect a debut at a minimum of 2.4GHz and probably at least one speed grade higher. Learning from their mistakes with the Pentium 4, Intel will balance the reduction in efficiency of a deeper pipeline with a wider 4-issue core (vs. the current 3-issue core used in Yonah).
So it looks like Intel's plan for 65nm is to rely on their deeper pipelined processors (Conroe/Merom/Woodcrest) for higher clock speed, with Yonah falling below the 2.5GHz mark. And based on what we've seen in the first article, a 2.33GHz Yonah would be competitive with an Athlon 64 X2 4600+, but definitely not outpacing it. This does bode well for Intel's next-generation processors, especially on the desktop with Conroe.
If the move to a 4-issue core is able to balance out the negative impact of a deeper pipeline (which admittedly it may or may not do in all cases), a higher clock speed desktop part should be very good competition for AMD's offerings. Although based on what we've seen thus far, we would be surprised if Conroe vs. Athlon 64 was a blow-out in favor of either manufacturer; more and more, it is looking like Conroe will simply bring Intel up to par with AMD, ahead in some areas, behind in others, and with the lower power advantage as long as AMD is still at 90nm.
Why the X2 and why not Turion?
One of the other questions that we were asked a lot after the first article was why we insisted on comparing a mobile Yonah processor to a desktop Athlon 64 X2, and not an AMD Turion 64. Our reasoning was obvious to some, but we felt it made sense to present it more clearly here:
Whereas the Pentium 4's extremely deep pipeline made clock-for-clock comparisons to the Athlon 64 virtually meaningless, the Pentium M and Yonah processors feature far shorter pipelines akin to AMD's architecture.
The Athlon 64 features a 12-stage integer pipeline, and while Intel has never specifically disclosed the length of Yonah's pipeline, they have made two important statements: it is longer than the Pentium III's 10-stage integer pipeline, and shorter than Conroe/Merom's 14-stage pipeline. Given the relatively tight range, Yonah's pipeline can pretty much be considered to be very similar to AMD's Athlon 64, give or take a stage of the pipeline.
The net result is that we can draw some valid conclusions based on comparisons of Yonah to the Athlon 64 X2 at similar clock speeds.
But our Yonah sample ran at 2.0GHz, which ends up being the speed of the slowest Athlon 64 X2 that is currently available: the 3800+. The highest end Athlon 64 X2s currently run at 2.4GHz, with high speeds just around the corner. So the question isn't just how competitive Yonah is at 2.0GHz, but rather, how high can Yonah go? Unfortunately, our test platform wouldn't allow us to overclock our chip very far, but thankfully, we have access to a decent amount of Intel's future roadmaps, so we can at least see what's going to happen to Yonah over the next year.
While Yonah will make its debut at a maximum speed of 2.16GHz, it will actually only receive a single speed bump before Merom's release at the end of the year. That means that we'll see a 2.33GHz Yonah after the middle of the year, but we'll have to turn to Merom to get any higher clock speeds.
Looking back to our initial articles on the Pentium M's architecture, you'll remember that one of the important aspects of its design is that all critical paths in the chip were slowed down to meet a maximum clock target. This means that Intel set a clock target for the CPU and made sure that the chip ran at that speed or below, and did not optimize any paths that would have allowed the CPU to run higher. Instead, the Pentium M team depended on the manufacturing folks to give them additional clock speed headroom by providing smaller manufacturing processes every 2 years. In other words, the Pentium M was never designed for high clock speeds, which is why it debuted at 1.5GHz and still has not even reached 2.33GHz today.
Intel's next-generation microarchitecture hopes to change that approach ever so slightly by introducing a longer pipeline into the equation, but on a much more conservative basis than the Pentium 4 did just 5 years ago. Conroe (desktop), Merom (mobile) and Woodcrest (server) will feature a 14-stage integer pipeline, which will allow for higher clock speeds than what Yonah could pull through. We would expect a debut at a minimum of 2.4GHz and probably at least one speed grade higher. Learning from their mistakes with the Pentium 4, Intel will balance the reduction in efficiency of a deeper pipeline with a wider 4-issue core (vs. the current 3-issue core used in Yonah).
So it looks like Intel's plan for 65nm is to rely on their deeper pipelined processors (Conroe/Merom/Woodcrest) for higher clock speed, with Yonah falling below the 2.5GHz mark. And based on what we've seen in the first article, a 2.33GHz Yonah would be competitive with an Athlon 64 X2 4600+, but definitely not outpacing it. This does bode well for Intel's next-generation processors, especially on the desktop with Conroe.
If the move to a 4-issue core is able to balance out the negative impact of a deeper pipeline (which admittedly it may or may not do in all cases), a higher clock speed desktop part should be very good competition for AMD's offerings. Although based on what we've seen thus far, we would be surprised if Conroe vs. Athlon 64 was a blow-out in favor of either manufacturer; more and more, it is looking like Conroe will simply bring Intel up to par with AMD, ahead in some areas, behind in others, and with the lower power advantage as long as AMD is still at 90nm.
Why the X2 and why not Turion?
One of the other questions that we were asked a lot after the first article was why we insisted on comparing a mobile Yonah processor to a desktop Athlon 64 X2, and not an AMD Turion 64. Our reasoning was obvious to some, but we felt it made sense to present it more clearly here:
- As much as Yonah is a mobile processor, it is a great indicator of the performance of Intel's future desktop processors based on the Conroe core. AMD has already stated that beyond moving to Socket-M2 and some minor updates, there will be no significant architectural changes to the Athlon 64 line next year. In other words, we know for the most part how AMD's going to be performing next year, but we have no clue how Intel will towards the end of 2006; Yonah helps us fill in the blanks.
- AMD will have a dual core Turion based mobile processor out sometime in 2006. However, it will be based on AMD's Socket-M2 platform, meaning that it will include DDR2 support. Given that we don't know exactly how DDR2 is going to impact the Athlon 64's performance, we couldn't accurately simulate the performance of AMD's upcoming dual core Turion. Comparing a dual-core Yonah to AMD's single-core Turion also wouldn't be too valid a comparison either.
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fitten - Tuesday, December 20, 2005 - link
Yup... as I posted above... the rumor is that Yonah was designed for 2.5GHz (maybe even 2.6GHz or so) and can easily be overclocked to those speeds but is being launched at the speeds it is for exactly what you say... to fit in a certain power envelope.Xenoterranos - Tuesday, December 20, 2005 - link
We'll, that's definitely a logical argument, but I'd say only marginally relavent to this discussion. If a laptop with X% better power consumption comes out, does it really matter in the end where those X% came from. I can see the validity in saying that maybe some of those optimizations are on the board and thus the CPU shouldn't be given all the credit, but lower consumption is lower consumption. But that's all hypothetical. The reality is that even without optimizations, the Pentium M would have enjoyed lower power consumption just by moving to the 65nm proccess, as would any proccessor. that's where most of that 30% came from. I'd venture to say that the board design provides 1 or 2 % max, and definitely within the margin of error.><eno
Xenoterranos - Tuesday, December 20, 2005 - link
Um, i got confused there a bit. I'm basically saying that the new "Core Duo" derives the majority of it's efficiency not from any architectual changes (although they do help a lot), but from the move to 65nm. When AMD makes that jump to (and if Intel hasn't already gone to 45nm) then you'll see AMD pull ahead in power consumption on all 65nm parts, if not performance as well. Remember, aside from the on-die controller, this new architecture is very similar to what AMD is doing. Like the author said, if they wanted to copy something, they should at least copy the serial bus!Betwon - Tuesday, December 20, 2005 - link
All one know that Dothan is 90nm.But it is very cool. hot == Intel's 90nm? No!The CPU's architecture of low power consume is key. We must understand that IC design is very complex, many advanced tech are applied to keep CPU cool, include the CPU's architecture(such as micro-ops fusion).
Furen - Tuesday, December 20, 2005 - link
Yonah is better? It seems to be like its a pretty even match clock-for-clock but if you consider that X2s max out at 2.4GHz (currently) and Yonah will launch in around 15 days at 2.13GHz (the FX-60 is supposed to launch around the same time, so the X2 max clock may hit 2.6GHz when Yonah arrives) then it is clearly inferior in the performance department. Granted, the power consumption is quite a bit better but I'd hardly say that the CPU is better, just better suited for low-power applications.Betwon - Tuesday, December 20, 2005 - link
Yonah(2GHz/L2 2M) is better than AthonX2(2GHz/L2 2M) in the many cases.Everyone also believe that Yonah is able to reach the very high frequency.
In the past, We also known that PM can be overclocked better than A64. The PM's best record of Super Pi is much fast than A64/FX.
Zebo - Monday, December 19, 2005 - link
Yonah Yonah Yonah... Nah it was hype as I suspected... these procesors are vitually identical to AMD's old A-64's.. AMD supposed to get signifigant bumps w. DDR2/3 and PCIe onboard plus I read about some technology AMD and IBM made to increase performance by a whopping 40%!!http://www.guru3d.com/newsitem.php?id=3370">http://www.guru3d.com/newsitem.php?id=3370
AMD has nothing to fear other than in power arena when longer pipe Conroe comes and even then that advantage may very well disappear.
IntelUser2000 - Tuesday, December 20, 2005 - link
The 40% advantage is TRANSISTOR performance. Even then, its 40% advantage when no straining is included at all. AMD has strained silicon in their current process. Which means real advantage is FAR less than 40%.Shintai - Monday, December 19, 2005 - link
PCIe onboard is not a speed advantage. It´s more a tactic move towards the the computer on a chip solution.AMD is keen on ondie memory controller and in some years PCIe aswell due to the fact they suck at chipsets. Sure nVidia is making some good ones now. But it´s always been Intels extra strong point.
PCIe would also gives less traces on the motherboard that gives lower cost. But your CPU will break the 1300pin mark atleast and will be unable to scale in any way. Like AMDs backwards setting with DDR. When some new PCIe or more PCIe lanes comes out. You would need a new socket.
However personally I´m in favour of it. I just think AMDs ondie solutions is the wrong way. On package seems alot better and more flexible. Until we have an even more stagnant development cycle for external parts.
stateofbeasley - Monday, December 19, 2005 - link
DDR2 advantage? I wouldn't count on it. The latency on DDR2 still sucks compared to DDR. I wouldn't be so quick to scoff - Yonah performs as well as the X2 while consuming only a fraction of the electrical power.I don't see why people thought Yonah was going to be some sort of X2 destroyer. Its execution core has far fewer units than K8 and it lacks an on-die memory controler. The fact that it can match an X2 with slimmer cores makes it all the more impressive. The only hype was in your mind.
The AMD/IBM technology is not in processors that we can benchmark today -- they have yet to bring this process to mass manufacturing.