i7-3770k memory channels

You can use two memory slots per memory channel, so 4 slots.

For DDR, DDR2, and DDR3, like IDE/PATA, you can have two *devices* per channel giving a maximum total of four, at least for consumer systems with two channels. DDR/DDR2/DDR3 allow for up to three modules per channel with registered modules and probably also fully buffered and load-reduced modules in servers and some workstations. Some systems also have triple or quad channel memory, granted that's mostly also in the server space except for Intel's *consumer* X58 (triple channel, up to two DIMMs per channel) and X79 (quad channel, up to two DIMMs per channel) platforms.

Basically, you can use all four slots in your motherboard, but it will not increase performance coming from two slots whereas goign to two or four from an odd number such as one or two will increase performance a little (or a lot, depending on the workload, but usually just a little).

To bring his excellent answer down to our level, get two ramsticks and place them in the same colored slots per your motherboard manual. This will get you maximum performance. Later, if you take up rendering movies or simulating quark interactions, you can double your ram with the other two slots.

A memory channel is a connection between a stick of memory and the memory controller. In the old days, memory controllers in desktops and laptops only had one memory channel- that is, they could only communicate with one memory module at one time even though the system might have two, three, or four modules. Adding a second memory channel during the early 2000s doubled the memory bandwidth as you could now talk with two of the memory modules at once. Three and four channel memory controllers can talk to three and four modules at once, respectively, and gives higher potential memory bandwidth.

How many sticks of memory you can have per channel depends on the type, generation, number of ranks, and speed of the memory as well as the memory controller itself. Unbuffered desktop SDRAM and first-gen DDR could generally handle 3 modules on a single channel and 4 modules between two channels. DDR2 and DDR3 are two modules per channel which explains why mini-ITX stuff like the AMD E-350 (single-channel DDR3) only has two RAM slots at most, dual-channel DDR3 parts like the i7-3770K have four slots, triple channel DDR3 parts like the i7-920 has six slots and the LGA2011 four-channel i7s have eight slots.

Server stuff gets much hairier as you have unbuffered vs. registered memory, multiple ranks and bit widths of memory ICs, varying voltages, and speed also plays a much larger role in module capacity.



Registered DDR3 allows for up to three modules per channel. Current implementations are limited to 8-10 ranks/channel which means you might only be able to fill two slots with quad-ranked modules and that's all she'll support even though there is an empty slot. Memory speeds drop like a rock with using two quad-ranked modules/channel as well. My Opteron 6234 will run up to DDR3-1866 with one single or dual-ranked 1.50 volt module per channel but drops to DDR3-800 with two quad-ranked 1.35 volt modules. Ouch!

Registered DDR and DDR2 supports at least 4 modules/channel, possibly more. I have only worked with the four module/channel boards (8 DIMM slots and two channels) so I can't say if that's the maximum. I seem to remember 16 DIMM slot DDR boards and 12 DIMM slot DDR2 boards, so it might be even higher. FB-DIMMs are a whole different ball of wax and their serial topology supported up to eight modules per channel, although performance was rotten beyond two modules/channel due to the latency. I have seen one quad-channel TYAN i5000X board with all 32 FB-DIMM slots present in a massive set of removable RAM cards. It was impressive, mainly that the "tower of RAM" dissipated about as much heat as a Bloomfield i7 with the screws turned to it.

Basically, you can use all four slots in your motherboard, but it will not increase performance coming from two slots whereas goign to two or four from an odd number such as one or two will increase performance a little (or a lot, depending on the workload, but usually just a little).

Click to expand...

Current CPUs running on a single RAM channel run at about 60-70% performance compared to dual-channel according to some Tom's tests in the past couple of years. Ironically the desktop triple and quad-channel i7s didn't perform any better with the full 3 or 4 RAM sticks compared to just two. The only CPUs that truly need more than two channels populated are the LGA1356/LG1366 and LGA2011 Xeons in multiprocessor setups and any G34 Opteron setup. The G34s are unusual that they actually have two CPU dies stuffed under their oblong heatspreaders. Each has a dual channel memory controller that needs to be fed to perform well.