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4x4 Chips, Opening AMD's Architecture
Nom du Keyboard writes "Once upon a time open slots in a PC that anyone could build a card for were a good idea. PCs with them sold better than PCs without them. Now AMD is proposing another new socket that will be open for plugging in of 3rd party co-processors directly on the processor bus." They've also announced a 4x4 chipset, meant to counter Intel's Core 2 Duo chips. From the article: "Socket 4x4 will have a more immediately impact. Set for a release in the latter half of this year, it essentially lets you combine two dual-core Athlon 64 X2 or Athlon 64 FX chips to create a quad-core desktop PC now ... AMD made the point that Socket 4x4 also provides a more flexible upgrade path for a single motherboard system by letting you start with one chip and add another later on. AMD didn't talk pricing, but you can bet neither the Socket 4x4 motherboards, nor systems that use it to include two dual-core CPUs will be cheap."
I thought the current dual-socket motherboards (eg this board) could already accept dual-core Athlon (well, Opteron) chips (eg: the 270 series) to make a quad-core machine ?
They can; 4x4 appears to be a new marketing label for the same thing. (Just as "Athlon" and "Opteron" are the same chip already.)
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A 4x4 truck doesn't have 16 wheels.
There is no FSB and the memory is LOCAL to the processor. How would this maintain coherency? The Athlon64 processors also don't allow cHT. Not that they don't physically have support for it, just it's been disabled.
Given where I work, and that I've never heard of this before today... I suspect it's a hoax.
The only way this would work is if the OS was aware of it and manually routed data from one node to another (e.g. like a northbridge DMA device you can pipe info to).
AMD's own slides from the 2006 analyst's presentation backup this information. If you look at the slides, it is pretty clear that AMD has enabled one ccHT link on some of the Athlon 64 X2 series. _slides_
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So, what's the difference between this and any other motherboard with two processor slots? Those have been around for ages. For that matter, Apple's highest model Power Mac has had two dual-core processors for some time now, so having dual dual-core processors isn't new.
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I believe what they're going to be offering is dual socket motherboards that take athlon rather than opteron pinouts.
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It's slides 69 and 73-74, to be exact (I can't believe I just looked at all of those).
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No, you missed the point. Opterons have activated one, two or three coherent HT links. That lets them keep their caches [and memories] in sync.
In a typical FSB MP system the processors snoop the bus and look for reads/writes.
In the opteron world the processors send out cache probes via the HT links. Athlons have ZERO cHT links activated which means they cannot work in MP systems.
Tom
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It's not a new socket, it's two Socket AM2s next to each other which accept standard AM2 processors such as the X2, which have a coherent HT link enabled on them for this use.
It's consumer version of a dual-processor Opteron motherboard, with a specific socket layout and memory system that's more directed at consumers. AMD will support this in 2007 with 4x4+ (2 quad-core processors on AM2) and in 2008 with 4x4++, whatever that may be.
These motherboards will also support two x16 PCIe graphics card slots, which if you configured using quad-SLI gives you the other 4. 4 CPU cores, 4 GPU cores.
It's mostly marketing to keep the high end benchmarks in AMD's hands, and thus the kudos, and then further sales.
Quite clear really, although I'm confused as to why AMD didn't go the MCM route on a single socket, like the Pentium D and the upcoming Kentsfield processors from Intel.
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nothing to do with anti-amd sentiments!
(just stating the obvious here, as it seems to be necessary)
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Just as "Athlon" and "Opteron" are the same chip already.
Has AMD started enabling multiple hypertransport links in the Athlon chips? Opterons have two or three hypertransport links, Athlons only have one link active. Yes, it is artificial, but that makes sure the people that are likely to need it are going to pay for the feature. The multiple links are needed to chain or mesh multiple CPUs together. Maybe the "4x4" chipset is another crosspoint switch to get around the limit of the single link, though it might add latency by adding another hop or two.
Um to be more correct all K8 processors have THREE HT links. The difference is whether they can act as coherent links. A 2xx series processor will have one link between processors and at least one to the northbridge I/O controller.
Tom
Someday, I'll have a real sig.
You will need a pretty recent version of Linux. I am running SuSE Linux Enterprise Server (SLES) 9 Update 2, except that I've upgraded the kernel to a 2.6.14 from kernel.org. My suggestion: go with the latest Red Hat Enterprise, or wait for SLES 10, due out any week now.
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