Quad channel memory?

Tri channel offers no real-world benefits. Triple channel modules are more expensive because people are stupid and don't buy an 8 GB kit and another 4 GB kit. RAM is dirt cheap nowadays.

For most applications you wouldn't even notice the difference between single and dual channel.

What applications benefit from tri and even quad-channel RAM?

From Tri-channel? Just benchmarks. Nothing in the real world can saturate or use all the bandwidth of dual channel. Quad channel would just be a waste of electricity at this point.

Dual, triple or quad channel doesnt affect the memory stick, that is all about how the memory controller is set up so a "quad channel" kit shouldnt be any more expensive than getting two dual channel kits.

Quad channel is used in some server boards already, AMD's G34 socket supports quad channel memory but this is mainly due to there being two dies per CPU so each memory controller in the CPU is dual channel, they just use different channels.


Quad channel will just boost the bandwidth, and most things are not bandwidth limited, improved latency would help more sigificantly than doubling the memory bandwidth, because it doesnt matter how large your bandwidth is, if you are only waiting on a 5KB block you are spending most of the time waiting due to the latency of the memory itself so i would much rather see a reduction in latency over increase in overall bandwidth. Unless you are doing stuff that calls to memory a lot like image or video processing or dealing with large arrays/databases you wont be able to saturate the cache of the CPU and caching is good enough these days that you dont miss often so memory performance above about 1066MHz DDR2 gains you very very little.

The new X79 chipset was designed as a server chipset. That's why it has quad-channel memory support. For whatever reason, Intel decided to give the chipset to us as well as the server buyers. The Sandy Bridge "E" CPU will quite powerful with a quad-channel memory controller and up to 15MB of L3 cache. It will also be quite expensive. It's the extreme-performance category, after all.

The mainstream CPUs (including Ivy Bridge) will still use dual-channel memory.

Technically, the new motherboards won't be quad-channel. They'll be dual-dual-channel, with a dual-channel pair on either side of the socket. That means you can just buy two dual-channel kits (same specs) and plug them in - no need to buy a special quad-channel kit of matched RAM. No more expensive per DIMM than existing dual-channel kits.

The tri-channel kits I've seen haven't been priced higher per DIMM than the dual-channel - some are very slightly cheaper per DIMM. If you've been charged more, then shop around.

Technically speaking, yes dual-triple-quad channel has nothing to do with the RAM itself, it's not an instruction set, nothing, it's just the way the RAM is used ... it's like RAID for RAM  . However, when you buy a memory kit, the speed, CAS and voltage is rated for that kit alone; this means that three (single DIMM) DDR3-1600 CAS9 1.5V modules sold individually might not be able to run at those specs compared to a single triple-channel kit with the same specs.

In the end it's usually a question of playing with CAS and voltage, but still the higher price is partially due to the fact that each individual module has to pass a harsher quality control process in order to work at the rated specs together.

The reason for the DIMM slots being on both sides of the socket is because with a quad-channel memory controller, it is more sensitive to trace lengths. Having them on both sides allows all of the traces to be shorter.

And while you can get two dual-channel kits, it's not recommended. Hell, even with today's dual-channel memory controllers sometimes two dual-channel kits don't work together.

My recollection is single- to dual-channel resulted in a general boost of 5% on average.

Safe to say the jury is still out on dual- to triple-channel. Some wheres out there on the internets I recall seeing seeing an article that suggested each perform at 10-11ns per cycle on average.

And ditto on what Leaps said. I'd be guessing that quad-channel would require some level of error-correction.

Like $1,500 expensive? Just for the CPU?

I would expect the top X79/SB-E/8-core cpu to be at least $1000, given Intel's history w/ $1000 pricing for flagship CPUs....

Figure another $300-$450 for a mainboard....

Sweet!  

The three initial SNB-E models will likely be $500, $700, and $1000. I don't think the mainboard will be that expensive though -- $250-$350 maybe.

The three initial models will include one four-core and two six-cores, all with Hyper-Threading. I've seen other people say there will be eight-core models, but I haven't seen anything myself that mentions that. The four-core will have limited overclocking, but the two six-core models will be fully unlocked.

What about the 8-core ivy bridge? Isn't the IB supposed to be the faster successor to the SB?

Yes, Ivy Bridge (IVB) succeeds Sandy Bridge (SNB). But Sandy Bridge "Extreme" (SNB-E) should still outperform IVB. It will likely take an Ivy Bridge "Extreme" (IVB-E) to beat an SNB-E.

IVB is still considered by Intel to be a mainstream product. SNB-E is their extreme-level product. They would probably introduce an eight-core SNB-E before they introduce an eight-core IVB.

Now it's looking like January 2012 for SNB-E and April 2012 for IVB. I wouldn't expect to see an eight-core SNB-E until June, and an eight-core IVB/IVB-E maybe in September. That's just a guess though -- like I said, I haven't seen anything about eight-core SNB-E or IVB chips. Even the existence of an IVB-E is just a guess.

Edit: We're getting a bit off-topic. Anything more about IVB and SNB-E should be posted in the sticky here.

The current P67 Sandy Bridge motherboard and chipset only has PCIe 2.0 x8 speeds (a bottleneck for enthusiast graphics cards). As well as only dual channel memory support. However, the X68 and X78 motherboards will solve that.

PCIe 2.0 x8 is only a bottleneck in the most extreme circumstances -- like in SLI or CrossFire when using huge multi-monitor resolutions like 5760x1200. If using a single monitor, it's not a bottleneck at all.

The X68 and X78 names have been scrapped. X79 is the final name of the chipset that supports LGA 1356, 1366, and 2011 sockets. The 1356 and 1366 sockets support triple-channel memory, and the 2011 socket has quad-channel memory. Only Sandy Bridge 'Extreme" CPUs will be available at launch.

The new chipsets for Ivy Bridge are B75, Q75, Z75, H77, Q77, and Z77. The all have PCIe Gen3 and native USB3. They use the LGA 1155 socket, so they are still limited to dual-channel memory.

It may not be so much of a bottleneck for a single GPU card, but the PCIe 2.0 x8 is a noticeable bottleneck for the HD 6990 and GTX 590. Even x16 speeds are barely enough to keep these cards smoothly running.

Next-gen motherboards from AMD and Intel will have PCIe 3.0 to keep all of the 1's and 0's the HD 7xxx and GTX 6xx series GPU's will be pushing through the PCI BUS. as well as the next-gen 8-core processors which will have to handle the astronomical throughput of the new cards.