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Print 59 comment(s) - last by peternelson.. on Jul 11 at 9:01 PM

AM2 motherboard owners rejoice, AM2 has a long future

AMD has released details of its next-generation desktop CPU interface, Socket AM3, to its OEM partners.  In a mildly surprising move, AMD has revealed that AM2 will accept AM2 or AM3 (also dubbed AM2+) CPU packages.  Additionally, recent roadmaps have confirmed that AM3, AMD's upcoming desktop CPU socket, will not be backwards compatible with AM2-package CPUs.  Roadmaps and memos have also confirmed that this AM3 package will be for AMD's "K8L" architecture, and not for the upcoming 65nm AM2 Brisbane CPUs scheduled for launch this December.

The most recent AMD roadmap is also very clear to state AM3 "supports either DDR2 SDRAM or DDR3 SDRAM, but not on the same motherboard."  This is great news for upgraders, as there is a very clear upgrade path: CPU, motherboard, and then memory.  This also infers that AM3 CPUs will have both DDR2 and DDR3 support on the integrated memory controller.  DDR3, like DDR2, has 240-pin, but the two formats are not pin-compatible.

As we also mentioned earlier, Greyhound will be the first desktop processor to support HyperTransport 3.0. Part of the specification for HT-3 is backwards compatibility with older revisions of HyperTransport, and the forward compatibility of the AM2 socket confirms that.  However, it’s important to mention that even though AM3 CPUs will work in the AM2 socket, HT-3 allows for 5.2 Giga-transfers per second, while current AM2 motherboards top out at 2.0 Giga-transfers per second.  Even though the additional headroom is likely not completely necessary, quad-core CPUs will certainly benefit from the additional bandwidth to additional CPUs or co-processors.

There is no word yet on the number of pins the new socket will require, but since AM2 sockets are forward compatible with AM3 CPUs, we can at least deduct that AM3 will have fewer than 940 pins.  Furthermore, since Socket AM2 is forwards compatible with AM3 CPUs, it is also safe to say that AM3 is not a land-grid array (LGA) socket.  AMD will switch its Opteron platform to an LGA-1207 socket on August 1, 2006.  AMD has not announced when Socket AM3 will be released, although since it would be the first HT-3 "ready" socket design, it seems likely that K8L and AM3 for the desktop will launch simultaneously.



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RE: AM2 Motherboard Royally Screwed Over
By Furen on 7/6/2006 1:51:47 AM , Rating: 2
I suppose I missed the info about the release date of socket AM3. Since AM2 is forward compatible AMD can release AM3 package chips without actually releasing the socket. Besides, even if a socket AM3 is available the fact that socket AM2 still drives those CPUs does not make it a dead socket, kind of like socket 754 coexisted with socket 939 but to a greater degree since AM2 will be able to drive all chips the chips in production.


By Furen on 7/6/2006 1:55:37 AM , Rating: 2
Ignore the first "chips" in the last sentence...


RE: AM2 Motherboard Royally Screwed Over
By hwhacker on 7/6/2006 2:06:37 AM , Rating: 2
Exactly. You can either look at it as when the chips are "replaced" by a higher-end chip when it enters the market, or when the chips go completely out of production. If the former, Socket 754 and 939 had a much shorter lifespan than that listed in the post above. If the later, then we have no idea when AM2 cpus will cease to exist, especially as budget alternatives ala Sempr0n. AM2 could very well go on to be the next 754, with a lifespan very short at the top, but long in the low-end.


RE: AM2 Motherboard Royally Screwed Over
By Furen on 7/6/2006 2:56:48 AM , Rating: 2
But it doesn't matter how long AM2 chips are in production. If AMD stops AM2 chip production next week and starts making AM3 chips that go into the AM2 socket AND into a future socket then it makes no difference. AM2 motherboards will probably become low-end but the CPUs on them will continue being high-end. Remember that DDR3 will be higher-latency than DDR2, and HT3.0 brings close to nothing to the desktop (power management with HT3/DDR3 is better, that's the only benefit I can see).


RE: AM2 Motherboard Royally Screwed Over
By gudodayn on 7/6/2006 3:03:20 AM , Rating: 2
quote:
Textand HT3.0 brings close to nothing to the desktop (power management with HT3/DDR3 is better, that's the only benefit I can see)


You know this becuase you've seen a working sample and actual benchmark scores of an AMD CPU running HT3 + DDR3 modules??


RE: AM2 Motherboard Royally Screwed Over
By Furen on 7/6/2006 3:25:31 AM , Rating: 2
Like I said, DDR3 is higher latency, there's no question about that. Remember the shift from DDR to DDR2? Expect the same. The few benefits from DDR3 are: the lower operating clock for the memory cells (Octo-pumped as opposed to DDR2's quad-pumped), a better production process (I'd expect, I'm not certain about this), and higher memory density later on. They're great benefits, to tell the truth, but nothing earthshattering on the performance side. The lower operating clock and better process will, of course, lead to lower power draw.

HT is simply a data transport, having it be faster gives you close to no benefit, in fact, lowering it to around 600MHz (from the current 1GHz) gives close to no penalty. So does let's see what HT3 beings us in comparison to HT 2.0:

AC/DC modes of operation, yeah this is useful...
Hotplugging, let's hotplug the CPU.
Link splitting/Unganging... not very useful in a CPU to NB connection, VERY useful to interconnect more than 8 CPUs, though.
2.6GHz max clock, very useful in 4-way+ systems, but do we really need 20GB/sec links to the NB?


By coldpower27 on 7/6/2006 11:19:09 AM , Rating: 2
Keep in mind that AMD could simply use the lowest of the HT3.0 specification, rather then the highest.

They don't have to go for the full 2.6GHZ clock rate of it.


By coldpower27 on 7/6/2006 11:16:40 AM , Rating: 2
Because this information is not too difficult to infer, HT advantages are that it allows a point to point connection and seperates the I/O bandwidth from the "FSB" and gives it, it's own line, while the memory bandwidth comes anoter avenue.

For desktop workloads more memory bandwidth, and more I/O bandwidth are 2 things that, while nice to have are not bottlenecks on K8 derived architecture.



RE: AM2 Motherboard Royally Screwed Over
By Fenixgoon on 7/6/2006 2:17:52 AM , Rating: 2
i love my S754 system... 754 allowed me to upgrade from socket A without breaking the bank and see a dramatic performance increase.


By dilz on 7/6/2006 5:47:38 PM , Rating: 2
I did the same. A mobo and CPU for the cost of a single S939 Venice 3200... couldn't be beat at the time!


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