Help me understand bus speeds

[Vague]

Hi. I'm confused on bus speeds, memory speeds and memory standards.

I'm looking at buying a Q6600 with a 1066MHz FSB and a Gigabyte GA-EP45-DS3R that lists 1200MHz memory standard and 1600/1333MHz FSB.

What kind of ram should I get? But how do these numbers relate? Can anyone point me to a decent explanation to help me figure out the most appropriate memory? Will CAS timings be noticeable from 5 to 4?

I will be doing a little bit of overclocking, but have never done it before. I'm planning on just messing with the cpu not the memory timings if that's relevant.

 

[Tigerbiten]

You have three bus speeds that are linked. MotherBoards, Memory & Cpu.
2x MoBo = Mem, 4x Mobo = CPU.

The classic MoBo FSB speeds are 266, 333 & 400 Mhz.
Which give you motherboard/memory/cpu speeds of 266/533/1066, 333/667/1333, 400/800/1600.

Now a Q6600 has a 9 multiplier and runs on a 266 Mhz MoBo FSB for a speed of 2.4 Ghz.
So to overclock it drop the multiplier and up the MoBo FSB.
I would aim for a 400 FSB speed for best memory throughput.
So.......
400 x 6 = 2.4 Ghz, No increase in CPU speed but a lot better memory thoughput.
400 x 7 = 2.8 Ghz, Very bog standard overclock.
400 x 8 = 3.2 Ghz, A nice easy overclock but you may need to get a good aftermarket heatsink.
400 x 9 = 3.6 Ghz, Perfect overclock but you may well need to watercool to get here.

As the memory runs at twice the speed of the MoBo, 400 Mobo FSB = DDR2-800 Memory.

Luck ............

 

[engiNURD]

My version of tigerbiten's post...

/*------------- <cut n paste> -------------*/
Formulas for Intel platform @ 1:1 settings: (base FSB speed is SDR, or single data rate)
c × [Base FSB speed] = CPU Clock speed (c = CPU Multiplier)
2 × [Base FSB speed] = RAM speed (DDR: double data rate)
4 × [Base FSB speed] = Effective FSB speed (QDR: quad data rate)

On Intel platforms, running the RAM higher than a 1:1 ratio with the CPU is, for the most part, useless, so don't bother trying to do so. If the BIOS does it for you, just let it. All you need is a 1:1 config, though. Here's some possible clock speeds (as always with OC'ing, your results will vary):

Q6600: 9 × 266 = 2.4Ghz, DDR2-533 << STOCK speeds
Q6600: 9 × 333 = 3.0Ghz, DDR2-667 << Nice OC
Q6600: 9 × 378 = 3.4Ghz, DDR2-756 << Good OC, near max for B3 stepping w/ good air cooling
Q6600: 9 × 400 = 3.6Ghz, DDR2-800 << Great OC, near max for G0 stepping w/ good air cooling

You won't notice a difference between CL4 and CL5, unless you're running benchmarks (and even then, the difference is negligible), so don't pay a huge price premium for lower latency.
/*------------- </cut n paste> -------------*/

Since the P43/P45 chipsets don't support DDR2-533, the next option is DDR2-667. However, DDR2-800 is priced similarly, if not better, and will allow for you to reach near max OC speed, should you choose to do so.

I'd recommend these sticks:
$50 - G.SKILL 4GB(2x2GB) 5-5-5-15 DDR2-800 F2-6400CL5D-4GBPQ

 

[Vague]

Thanks for these explanations. I really appreciate it.

 

[Dangman]

My version of Enginurd's post:

Stated FSB/4 = Actual FSB
Actual FSB x 4 = Stated FSB
Multiplier x Actual FSB = CPU Speed
1:1 Ratio: 2 x Actual FSB = RAM Speed
1:1 Ratio: FSB = 1/2 RAM speed
Note that C2D systems don't see a performance increase with any ratio higher than 1:1

Q6600:
Multi x Actual FSB, Stated FSB, RAM Speed = Clock Speed
9 x 266Mhz, 1066Mhz, DDR2 533 RAM = 2.4Ghz <== Stock Speeds
9 x 333Mhz, 1333Mhz, DDR2 667 RAM = 3.0Ghz <== Good OC
9 x 400Mhz, 1600Mhz, DDR2 800 RAM = 3.6Ghz <== Excellent OC, About the Max