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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ozzimark - Monday, December 19, 2005 - link
they've got some headroom with clocks to play with, as the recent opterons are showing ;)Beenthere - Monday, December 19, 2005 - link
...and I'm sure some gillible sheep will buy into it.Since the "review" tested apples to oranges AGAIN, it's not of much value for anyone looking to purchase a notebook PC because you used a desktop X2 for comparison to Intel's YAWNER -- a dual core laptop chippie.
To quote this story:
"Intel’s Core Duo launches in January at CES, so if you’ve been thinking about buying a new laptop, we’d suggest waiting at least another month or so. You won’t be disappointed. "
-- Now if that ain't fanboy, what is???
Obviously with Turion stealing a lot of sales from Centrino, it's no surprise Intel is stroking the media to gain as much positive hype on uncompetitive products as it can since it knows it will be at least '07 if not later before it can compete with AMD in any market segment based on performance, value and power consumption. That however won't stop the Intel shilling.
stateofbeasley - Monday, December 19, 2005 - link
AnandTech is one of the most fair review sites on the net and has been one of the biggest champions of AMD products for years. Your "comments" are little more than pathetic insults against Anand, who is and always will be more credible than you.Furen - Monday, December 19, 2005 - link
I think that he is right to some extent, though. I was hoping for a power consumption comparison between Dothan and Yonah to see which one is better for battery life but it never materialized. I would not say that AMD has a Turion that can compete with Yonah but testing Yonah in a desktop setting and then concluding that it's a heck of a laptop chip without comparing it to other laptop chips leaves a bit to be desired. Also, the tone of this review seemed a quite a bit more Intel-appeasing, if you please, as there was nothing in this review that we didn't see before except for flowery praise about how Yonah does very well without an on-die mem controller.That said I must say that all the asking for a 2GHz 1MB L2/core A64 was pretty retarded. There is no 2GHz 1MB/core SKU so including a fake one just for comparison does not really help since there's no way to get something even similar (the 4400+ is the lowest-clocked 1MB L2 X2). It would have been nice to see an X2 4600+ (the second-best A64 SKU) compared to this Yonah (the second-best one) but I guess the 4200+ is more inline with its price.
SpinJaunt - Wednesday, December 21, 2005 - link
An overclocked Opteron 165 or underclocked Opteron 175 might have been an idea? forget about prices.
I think AMD still has some tricks up there sleeves regardless of what there roadmaps might say.
Anemone - Tuesday, December 20, 2005 - link
Eliminating clockspeed and using the best cache available sets the baseline for comparison, by keeping as few items of difference between the chips as possible. I fully agree with the choice, and, moreover, am quite positive there will be something out in the Turion line that will be quite similar to the 2ghz, dual channel, 1m/core cache that was used for testing.I think it's kind of funny to see us finally returning to tests where comparing close to exactly the same clockspeed produces even mildly comparable results. I say that because years ago that's what we used to do all the time, and finally things have come nearly full circle.
:)
Furen - Tuesday, December 20, 2005 - link
Ah, but we still don't know how DDR2 will affect K8 (or K9, as AMD likes to call the dual-cores) performance. Maybe AMD will increase the L2 cache data width from 128bits to 256bits (the Pentium M has a 256bit interface) to make up for the additional latency, though I doubt it.vijay333 - Monday, December 19, 2005 - link
"Now if that ain't fanboy, what is???"It's called giving good advice. Not an Intel owner myself, but even I would appreciate this info as AT obviously has more info on this. Would you rather buy a laptop now and then regret the purchase when something much better comes along in just a month from now? AT is not telling you to buy an Intel based machine, just to wait a month to get a better idea of what your options are. If you have read AT for a while, you should know that they are definitely not biased towards Intel...
tfranzese - Monday, December 19, 2005 - link
Something new and better will always be out "a month from now". Get use to it.bob661 - Monday, December 19, 2005 - link
Looks like just a P-M with two cores to me. Whoop-de-doo.