Power psu questions

[PcMojo]

I'm putting together a new system and have been able to answer most of my questions just going through the archive of articles here. I'm currently (subject to change) thinking of an i5-2500k with a Gigabyte Ga-Z68AP-D3 mobo. I had a few questions about Ram memory. Intel's web site states that the 2500k, which is relatively new, lists compatible ram memory as DDR3-1066/1333. I couldn't believe 1666 wasn't on the list.The mobo lists all speeds from 1066-2133. After reading Bilbats comments about latency, I'm now on the hunt for CL7 (or lower) ram. I'm assuming I'll get 1333. My mother board specs said it supported dual channel ram. In theory, it has another communication/transportation channel and will be twice as fast as just having one. I'm trying to understand how it works, especially with 4 memory banks.
Question: Exactly when am I using the extra channel?
With dual channel boards they color the banks in two different colors. Banks A and C will be one color and B and D will be another color. When you install your first Dimm kit, you are supposed to put them in banks A and C. If you get more later they go into B and D.
Questions: Does this mean one channel is actually A&B and the other B&C? The store I am buying my memory from lists over 200 types of memory and only one says dual channel. Is this an old or new technology?
Any help would be appreciated.

 

[alvine]

i have a 2550k running with 8 gigs of 1600 memory. you would buy higher rated speed ram when you are overclocking because in the past for a value oriented customer with a locked cpu you had to raise the front side bus and that would raise the ram speeds aswell. higher rated ram would ensure the ram wont hold you back when overclocking, but now with the unlocked K processors (i dont include extreme series because i will never pay 1k for a cpu) you raise the multi of the cpu leaving the ram alone (better oc) and once you get your desired cpu oc then you would start tweaking the ram

as the questions of two memory banks running faster than a single one thats a part of the design (dual channel memory controlers). if you notice the higher end x79 motherboard uses a tripple memory channels (you have 6 slots in total) so basically when you run your memory in a dual channel mode you take full advantage/better speeds of your ram by spliting reading and writing short term data across two memory modules (looking at the motherboard slots going from left to right it would look like 1 2 3 4. you would run them in 1 and 3 or 2 and 4 or occupy all of the ram slots provided)

 

[psaus]

Question: Exactly when am I using the extra channel?

When you install 2 or 4 identical memory modules correctly.

With dual channel boards they color the banks in two different colors. Banks A and C will be one color and B and D will be another color. When you install your first Dimm kit, you are supposed to put them in banks A and C. If you get more later they go into B and D.

Me being particular, you should use the term "slots" instead of "banks" as per the context above. Banks are something all together different, but willing to explain if you're curious.
But essentially you're right. The manual states for this board to start with your first kit in the white slots and your second kit in the blue slots.
If you examine the board closely, you'll notice that these white slots are labeled 1 and 2, and the blue slots 3 and 4. But if you were to read them in order (starting from the slot closest to the CPU) it would go: 4, 2, 3, 1. 1&3 are channel A and 2&4 are channel B.

The store I am buying my memory from lists over 200 types of memory and only one says dual channel. Is this an old or new technology?

Dual channel has been around for a while, so it should be easy to find. What you may be discovering is that the reseller either has bad descriptions on their site/store, OR you're seeing the more common reference of "kits". If you buy in kits of 2, consider that dual channel friendly.

I'm trying to understand how it works, especially with 4 memory [strike]banks[/strike] slots.

If you're going to build this initially utilizing all 4 slots, buy 4 sticks of the exact same thing, or 2 kits of 2 (=4 sticks total).
Note: You can install 2 modules at day 1 of X capacity, and install 2 modules a year later of Y capacity without problem, as long as the new modules are identical to the old except capacity (e.g., 2x 2GB day 1, 2x 4GB year later).

I couldn't believe 1666 wasn't on the list.The mobo lists all speeds from 1066-2133.

1333 is the highest standard speed set by JEDEC (RAM standards body). Everything above is overclocking. Motherboard mfgs and RAM mfgs support OCing on some of their products. But AMD/Intel will void your warranty in most cases.

Lastly,

In theory, it has another communication/transportation channel and will be twice as fast as just having one.

Theoretically yes. Real world, not so much. Still install in dual channel configurations for best performance, but don't expect to see 2x the difference.


Hope this helps some. Do reply if something is unclear or if you have any other questions.

 

[PcMojo]

Thanks for both your responses!
@alvine: I've often thought of OCing, but was to afraid my pc would melt. I think I will with this build just to get the benefit of faster ram speeds.

@psaus :I think I am starting to understand, but I am still unclear on exactly when the benefit of dual channel is realised. If I have 4 slots and put in two dual channel Dimms ito the correct colored slots (leaving the other two empty), am I getting the benefit of dual channels? Or does that just kick in when I put in the second set, slots 1&3 being one channel and 2&4 being the second? Those are my questions from a theoretical level - just trying to understand how it works. From a practical level, as it relates to my current build, if I built two systems exactly alike and in one put two 8Gb dual channel dimms in the proper slots, and the other system 4 4Gb dual channel dimms of the exact same type and speed, how much ram speed difference would you think there would be between the two systems and how would that translate to the overall speed of the PC? (1%, 10%, etc)

 

[psaus]

No problem. That's what this forum is all about.

In simplest of terms, if you install 2 identical modules per the instructions of your mobo, you will be in dual channel mode. As I stated above, you will be installing in slots labeled 1&2, but in visual order it will "look" like 1&3. But this can vary from board to board. Again, the above instructions are based on your manual.
I know most of us techies hate to read manuals, but I suggest having it open for CPU and RAM installation. If you follow those instructions, you'll be in dual channel mode (e.g., the optimal configuration)

As for your last question:

if I built two systems exactly alike and in one put two 8Gb dual channel dimms in the proper slots, and the other system 4 4Gb dual channel dimms of the exact same type and speed, how much ram speed difference would you think there would be between the two systems and how would that translate to the overall speed of the PC?

Technically speaking the faster system would be 2x8, but this has nothing to do with Dual channel vs single channel. It has to do with loading the bus - I will leave it at this simple description for now, and if you really want to get into the details we can.
How much faster? 1-2%? If even that fast. You wouldn't "see" the difference unless you did lots of performance benchmarks.

 

[PcMojo]

Thanks, that helps. I was afraid you were going to tell me the 4x4 would be faster. I would much rather pay extra for the 2x8, then if need be I could just add another set later. Any advice on where to buy DDR3? The store I'm getting most of my parts from doesn't give much as far as the specifications on the ram. After reading Bilbats posts on latency I tried to find cl7. Out of 150 or so types of ram, the store only had one or two that even mentioned the latency.

 

[psaus]

Depends on where you live - newegg if you live in the US. ebuyer in the UK. Let us know where you are.
CAS 9 is average, anything lower costs more money, and CAS7 is simply hard to find. Frankly, unless you are trying for overclocking braging rights, you don't need any lower than 9. 8 maybe, but 7 is for the extremist.
Corsair, Kingston, Crucial are my preferred vendors, but I'm sure there are others that can add to that list.