What am I missing with DDR3?

[hennethannun]

So I understand that DDR3 is out now and runs at extremely high speeds (1600-1800mhz at the top end), but i am confused as to the utility of such speeds.

My understanding was that Intel quad-pumps their CPUs, so that a FSB clock of say 333mhz results in a CPU speed of 333x4=1333mhz (ie the newest C2D chips, E6X50 and penryn). But DDR memory is only double data rate, so the same FSB speed of 333mhz results in a memory clock speed of 667mhz (DDR2-667/PC2-5400). So something like DDR2-800 memory is only fully ultilized (at a 1:1 ratio) if you run your FSB at 400mhz.

If that is the case with DDR3 memory, then what is the usefulness of DDR3 at 1600mhz? who can get their FSB up to 800mhz to take advantage of the increased speed? sure, you could set up a memory divider, but that doesn't seem to be worth while.

I'm sure there's something I'm missing here, but I can't see what it is.

 

[BonzaiDuck]

I'm very busy, but came in here for a second to post about some Crucial RMA replacement modules.

Off the top of my head, there are some memory operations that don't include the CPU in the loop. For those operations that do, running the system with a memory/multiplier-divider other than 1:1 would have "slack" with some unused clock cycles.

I've done some synthetic bandwidth tests using a 4:5 divider -- best "second-choice" for DDR2. For DDR3, add another second-best option of 1:2.

The benchies show equal or higher bandwidths and lower latencies running DDR2-800 or 1000 modules between 800 and 1000 Mhz. Some "Hot-dawgs" here at the forums -- extreme over-clockers -- try to push the DDR-1000 or 1066 (or better) modules beyond their spec, just as I push my DDR2-800's beyond their spec. This still means loosening the latencies, or increasing VDIMM to get the tightest set of looser latencies for the higher speeds. But comparing to 1:1, I come pretty close to the benchies for that divider with 4:5 running at 1T command rate (both ratios). The VDIMM requirements for the 4:5 ratio can be a notch lower than those for the 1:1 ratio.

As per "synthetic benchmarks" and remarks saying that "synthetic doesn't affect real world performance," I've found that my gaming experience has improved with the 4:5 divider to rival the (subjectively assessed) performance at 1:1. So this gives you more over-clocking options -- maybe with less stress on the Northbridge chipset, less voltage-stress to the memory.

For benching between the different dividers, it has been my experience that once you've found the VCORE setting for some OC using a 1:1 ratio, you can count on the same VCORE and speed for the other ratios (in my case, 4:5). So you can focus on stress-testing with "Blend Test" to discover shortcomings in your memory settings for those different speeds.

I can't speak from experience about DDR3 beyond what I've read. I can say this: The suckers are just way too expensive now; the technology is still not matured; and if you want DDR3, best to wait until some reviews point to some manufacturer (Crucial, OCZ, Mushkin -- whatever) with the best benchies on their high-performance RAMs.

You'll see that some motherboards have been released in two flavors for the same basic model: i.e. (and z.b.) -- ASUS has come out with two versions of the Maximus, and as I recall, one of them uses DDR3 while the other uses DDR2. Some boards provide for using either (but not both) of the two memory standards, but these hybrid boards will suffer from trying to be "all things to all people."

Check the CPU PowerUser Magazine review of DDR3 modules -- last month, I think -- fairly recent within the last few months . . .

Eventually, Intel will release processors capable of stock FSB settings of 1600. You got some decisiions to make with your "surfing the techno-waves" to trade off speed, price, availability, and inconvenience with chipsets, BIOS revisions and other things that have not yet matured.

I'm sittin' out there on my board in the water, but not paddlin' yet, and watchin' for dem waves, Hot-dawg!!

 

[NinjaJedi]

I agree that the price/performance is not there yet. With that said some reviews say that to get the full potential out of the x38 chipset the DDR3 boards are the way to go. This is probably only for extreme over clockers or benchers. For everyday use and gaming it is not a big improvement from what I have read. I have seen the price of some kits come down to what prices for DDR2 were at one year ago.
Here are 2 of the best deals for DDR3 right now. If you can call it a deal. I paid more for my DDR2 6400 last year.
http://www.ncixus.com/products...PVS32G1600LLK/Patriot/
http://www.tigerdirect.com/app...pNo=3403298&CatId=3485

 

[BonzaiDuck]

I was shelling out those prices for 2GB kits of DDR-500 OCZ "Gold ELs." I'll never do that again. Eventually the Gold ELs were RMA-replaced with Platinum XTC's sporting tighter latencies (very small improvement) and the same DDR-speed spec. I held on to the XTCs and never used them, migrating instead to those OCZ Platinum EL DDR-400's with the Aeneon chips. When I finally sold the XTC's, I took about $100 for them -- at today's prices, which are still high for DDR's older technology, but they're not much in production anymore -- therefore harder to find.

So I don't know what to say about springing for the mobos and memories oriented to DDR3 technology. This hobby can give your wallet a hemmorage like a sucking chest-wound (as my Vietnam vet friend used to call it.)

 

[hennethannun]

Those are just about the best prices one can find for high speed DDR3 with decent latencies, but there really is no point in spending $300 for 2GB of high speed ram when you can spend $100 for 4GB of 4-4-4-12 DDR2. Eventually DDR3 will be the way to go, since those bandwidth benchmarks show that it is going to be significantly better than DDR2 at high speeds AND Nehalem will have an integrated memory controller that should allow it to actually take advantage of that extra bandwidth, but right now it doesn't really seem worthwhile to spend 3x as much money on memory and probably an extra $100 or on the motherboard just to get super high speed DDR3 that needs a 3200mhz CPU that hasn't even been roadmapped yet (let alone built). Anyway, thanks for the answers guys! I'm glad to know I wasn't missing anything obvious or important about DDR3.

 

[Foxery]

Well, no... strictly speaking, each generation of RAM operates at the same frequency, but transfers double the data on each clock cycle. (DDR stands for Double Data Rate)

Old SDRAM = 133, 166 or 200MHz, 1 piece of data sent per clock
DDR1 = 133, 166 or 200MHz, but 2 pieces of data sent, so it's rated as 266, 333, and 400.
DDR2 = 133, 166 or 200MHz, but 4 pieces of data sent, so it's rated as 533, 666, and 800.
DDR3 = 133, 166 or 200MHz, but 8 pieces of data sent, so it's rated as 1066, 1333, and 1600.

Enthusiast chips turn that up to 233 or 266 MHz, with the appropriate multiplier. I'm not sure why DRAM technology isn't able to reach higher actual operating frequencies, but right now, this is how it is progressing. This should also give you some ideas of why performance differences between generations are nowhere near as exciting as they sound on paper!