What's AM2?

As we've mentioned before, AMD's Socket-AM2 is a brand new 940-pin socket that will add DDR2 support for all desktop AMD processors. There will be AM2 versions of Athlon 64, Athlon 64 X2 and Sempron CPUs. All of these are internally known as the Rev F core. When AM2 launches in June, AMD will offer official support for DDR2-533, 667 and 800. As of today, the fastest DDR2 that Intel officially supports is DDR2-667; however, by the time Conroe launches in Q3, Intel will also add DDR2-800 to the list.

What this means is that if you're planning to build a new system later this year - whether it is AMD or Intel based - then you'll be in the market for DDR2 memory. AMD has effectively kept regular DDR-400 quite alive and actually created a market for even faster DDR1 memories with their Athlon 64, but after June that's all going to change. With a single memory standard to support both players in the desktop market, things are going to get a lot simpler. It will also mean that we'll start to see more focus from memory vendors on DDR2, including cheaper variants as well as even lower latency offerings. We'll address whether nor not DDR2-800 is actually needed shortly, but like it or not, if you want a solid upgrade path for the future you'll be looking at investing in some DDR2 memory regardless of whether you choose AMD or Intel.

Alongside DDR2 support, the new Socket-AM2 CPUs add support for AMD's Pacifica Virtualization technology - AMD's answer to Intel's VT. While the two technologies aren't directly compatible, given the respect that AMD has gained over the past few years you can expect software developers to support it. Virtualization will become increasingly more important as time goes on, as we have already seen in recent announcements of Intel VT support on Apple platforms.

The third thing that AM2 brings us is what AMD is calling their Energy Efficient microprocessors. Certain SKUs of AM2 processors will be binned according to their power consumption and grouped into two categories: 65W and 35W. Both TDPs, interestingly enough, are competitive with what Intel is targeting for their 65nm Conroe processors. What's even more impressive is that there will be an Athlon 64 X2 3800+ that's available at both 65W and 35W TDPs, compared to the standard 89W TDP. The chart below will give you an idea of what the new dual core AM2 CPUs are:

CPU Clock Speed L2 Cache Size TDP Options
AMD Athlon 64 FX-62 2.8GHz 1MBx2 125W
AMD Athlon 64 FX-60 2.6GHz 1MBx2 125W
AMD Athlon 64 X2 5000+ 2.6GHz 512KBx2 89W
AMD Athlon 64 X2 4800+ 2.4GHz 1MBx2 89W or 65W
AMD Athlon 64 X2 4600+ 2.4GHz 512KBx2 89W or 65W
AMD Athlon 64 X2 4400+ 2.2GHz 1MBx2 89W or 65W
AMD Athlon 64 X2 4200+ 2.2GHz 512KBx2 89W or 65W
AMD Athlon 64 X2 4000+ 2.0GHz 1MBx2 89W or 65W
AMD Athlon 64 X2 3800+ 2.0GHz 512KBx2 89W or 65W or 35W

In the future you can also expect an FX-64 along with 5200+ and 5400+, but the chart above is what will be launching in the near future (the exception being that the 65W 4800+ that will launch in Q3).

There will also be single core Athlon 64 and Sempron AM2 processors, but we're still waiting for their confirmed specs. Given the specs of the Athlon 64 X2s, you can expect the AM2 Athlon 64s and Semprons to be identical to their Socket-939 counterparts. We'll also finally get retail availability of faster Sempron parts - current socket-939 Semprons are only available with OEM systems.

AMD has already indicated that it will not brand the 65W and 35W parts any differently than the normal 89W Athlon 64 X2s; they will simply have a different part number and carry some sort of lower TDP designation on their box. Of course, they will almost certainly carry a price premium, so that at least should help to differentiate the models somewhat.

As far as major architectural changes go, we haven't been able to find any surprises in any of our AM2 samples. L1 and L2 cache latencies remain unchanged from their Socket-939 counterparts.

You will also notice that AM2 and Socket-939 CPUs appear to carry the same model numbers, meaning that an AM2 X2 4800+ runs at the same speed and has the same cache size as a Socket-939 X2 4800+. Either AMD is being very conservative with its model numbers or we shouldn't expect to see any major clock-for-clock increase in performance with AM2 processors.

Index The Test


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  • flemlion - Monday, April 10, 2006 - link

    This seems to be just a quicky review. In the conclusion it is mentioned that the usefullness of memory bandwith increases as the CPU clock speed increases. But still a lower speed was used for this test than for the DDR1-400 versus DDR1-500 evaluation. It seems to me at least this test should either have been done at different speeds to get a feel of this impact or at minimum at the same speed of the DDR1-400 versus DDR1-500 article.
    As a sidenote, it's also interesting to see that the test config has no mention of the CPU speed that was used. If this is NDA, then say so, if not it just appears as hiding the details that would expose this article as gossip instead of information.
  • andrewln - Monday, April 10, 2006 - link

    I meant...
    Intel will see how the next generation of AMD works just 5% faster....wouldn't they tune down conroe to match or make it just a bit faster than AMD and sell at the premium price? Since the demand will be almost the same.
    1) AMD fanboi will keep on buying AMD
    2) Intel fanboy will keep on buying Intel
    3) But this time, people that wants performance, will be buying Intel (even though its only a 10% faster than the competitor, or 40$)

    This way, when AMD makes a new gen of procesor, Intel only have to tune up Conroe which is cheaper than making another big modification that might or might not work.
  • Conroe - Monday, April 10, 2006 - link

    They said 20%, and thats where they plan on staying. Theu could have more. The FX-62 has extra cache, it may give 10% who knows? Reply
  • Anand Lal Shimpi - Monday, April 10, 2006 - link

    Every FX-62 I've seen hasn't had any more cache than what's in the table in the review.

    Take care,
  • Dfere - Monday, April 10, 2006 - link

    I’ve got to disagree- I don’t think this makes sense to even upgrade from a 754 system to AM2.

    Why? Because if you remember Nforce 2- and all the Mb’s with “future- proof” DDR-400 systems, the MB makers did not live up to their claims. For most recognized mfg’s it took the revision after DDR-400 memory was available before most of them got it right.

    So I don’t see where AM2 can even be thought of as an upgrade path, especially before final revisions have been made in silicon. A MB you buy initially might work, but with future memory or processors… forget it. Anybody wanna take a bet ($1 will get you $10), that the first MB’s out by lets say- ASUS, do not allow for different memory timings or the latest memory say March of 07?, let alone a top of the line processor, same date?

    While the author did say many changes are still in the works, final silicon may not yet even been achieved. How can buying a MB now be considered a possible upgrade in the future?

    For this reason, and many price/performance reasons, I have a 754 system, and I will hope that after tax season ends I can build a 939 for a better price. That’s it.

    The numbers per the review state this clearly. This is not about performance. And it will be expensive. The analysis on the forum here site seems to indicate that the relative analysis is expected future performance, when Anand admittedly and AMD (by not making announcements about performance) seem to indicate (and I explicitly do) that this is not about performance…. Yet either. So how can this even be recommended as an upgrade path when there is very little real world benefit and future compatibility a MB purchased now and memory or processors is not even known.

    I am an avid fan of AMD, but I think excess hype can kill a product as quickly as bad rumors.
  • HammerFan - Monday, April 10, 2006 - link

    I'm suprised that nobody has considered the bottlenecks in AMD's systems as of late. Recently, it seems that all AMD really needs to do with the K8 is keep squeezing more MHz out of it. Clearly the CPU has enough memory bandwidth to spare, so bring the rest of the processor up to speed. IIRC, AMD is starting to implement an improved version of SOI in their new CPU cores (or is it 65nm cores?), which will help increase clock-speed headroom. Also, as quality continues to improve, AMD might be able to add higher clock speeds to take advantage.

    just my $.02

  • ozzimark - Monday, April 10, 2006 - link

    one thing that would REALLY help K8... follow intel's footsteps with netburst and try to double-pump the ALU. faster SSE execution never hurts either :) Reply
  • still - Monday, April 10, 2006 - link

    Double-pumping the ALU is only going to limit scaling and increase heat... what the K8 core really needs is better L1 and L2 cache subsystem.... The L1 is sort of ok but getting old it the same one the K7 (7 year old). They improved the L2 of the K8 over K7 but half heartedly. It still has too narrow of a path and too high of a latency. I can just imagine what the K8 can do with a 4M low latency cache that has 256 or 512 bit width data path (+ ECC of course).
    While they are there lower the L1 latency to 2 cycles. That alone is 5-10 % improvement.
    And they need to seriously improve the SIMD execution units. The current AMD SIMD units are almost as lame as the Intel implementation of AMDs 64bit instructions.
    Oh yeaa and write some decent compilers to make use of the 64 bit goodness like extra register - where are the promised 20 % improvements?
    The K8 core can scale better than Conroe and can crunch trough more instructions/data if the cache subsystem can feed all these to the execution units. Albeit the K8 has to be clocked slightly higher to do that - such is the tradeoff of 3 vs. 4 IPC.
  • mino - Tuesday, April 11, 2006 - link

    1) 3-cycle L1 on K7/K8 is the fastest required, it goes from the internal structure if the scheduler and the pipeline that 2-cycle chache would do almost no good. Also they would have to reduce L1 size to 32k+32k which would hurt. It simply does not make sense to change L1 at all, maybe on K8L but IMHO 128k+128k would help much more than 2-cycle latency.

    2) 17-cycle L2 is PRETTY GOOD for 1M L2 with exclusive structure!!! IMHO it is possible to do 16-cycle, maybe 15, but nowhere near Dothan's 10-cycle. Also remember lower-latency L2 has scaling problems (that's why intel made prescott's L2 slower than NW's)

    3) Concerning the memory subsystem(caches + memory) (on single-socket K8/K8L) the biggest issue is the robustness(amount of on the fly acceses to memory) and latency of the memory controller. To solve this is not trivial thing. IMHO to add 2-4M L3 with random access ~50 cycles would do.

    4) In the >4 sockets front all they need is effective caching of MOESI snoops.

    You are also forgot K7/K8 is mostly KISS architecture. It is just wery well balanced so has good performance in the end. However do one wrong change and you are screwed.
    KISS == Keep It Simple Silly

    About "weak" SIMD implementation on AMD, don't fool yourselves guys. Only x86 architecture faster than K8 on SSE/SSE2 is Netburst aka SIMD-by-intel.

    About conroe, ita has twice as wide ALU's and FPU's than PIII/K7/K8, this means it has huge resources at disposal to calculate SIMD.
    Same goes for K8L 2 quarters later. That said K7/K8 core has far more FP power than P6 architecture. On FP Conroe and K8 are about aquall.
    but K8L will wipe the floor with K8 and Conroe on FP. Conroe will wipe K8 on INT and be still faster than K8L by decent margin.

    Overall we are for another PIII vs. K7 battle with single very important change - AMD has a platform it had not back in the K7 vs. PIII days.
  • fitten - Thursday, April 13, 2006 - link

    I find the K8L a somewhat odd strategy. I guess they are targeting the Itanium market because Opterons already have a good part of the HPC market. Given that the HPC people are the ones that really care about FPU performance and that they are still a fairly small market segment, it seems an odd target. Integer performance rules the roost for servers... web, database, and just about everything else you can think of other than number crunching simulations and the like. Desktop uses for FPU are a few like games and some mathmatical stuff. Intel is focusing on integer performance at least as much as FPU with Conroe (Conroe gets a good dose of both), which makes sense to me since so much of the work done on computers, both desktops and servers, is dominated by integer operations. K8L speculation says only FPU horsepower will be added... just doesn't seem like a sound decision to me. Reply

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