There are many ways to go about overclocking RAM. The first step is always the same; figure out what speed it is running at, and what speed it is meant for. Often people set up new computers and 'miss' the RAM settings. Figure out the rated speed of the RAM by looking on the module or manufacturer's product page. Then fire up CPU-Z and check the FSB on the first tab and memory speed on the memory tab. CPU-Z has the ability to detect the speed of asynchronous memory buses (when the FSB speed and memory bus speed do not match) which is something the popular tool WCPUID lacks.
In the simplest situation RAM speed is synchronous to FSB speed. In this situation, all you have to do to overclock RAM is to raise the FSB speed. Some chipsets support asynchronous memory speeds. Think of the relationship between FSB, CPU speed, and multiplier, the situation is similar with FSB, memory speed, and memory ratio. The biggest difference is that the numbers for memory ratio are a lot smaller than for CPU multipliers, some are even below 1. Here is an example:
quote:
200MHz FSB speed with 100% or 1:1 FSB : Memory ratio results in 200MHz memory speed (DDR400)
200MHz FSB speed with 120% or 5:6 FSB : Memory ratio results in 240MHz memory speed (DDR480)
250MHz FSB speed with 80% or 5:4 FSB : Memory ratio results in 200MHz memory speed (DDR400)
Say your motherboard can't run a high FSB, but your memory can. You could change the ratio so that your RAM is overclocked highly while still staying within the constraints of what your motherboard can handle FSB wise. The downside is that in most situations synchronous FSB and memory buses exhibit higher performance than asynchronous speeds which are actually higher. The key is to test each combination to determine which is best on your motherboard. SiSoft's SANDRA offers a memory bandwidth test and any general system benchmarks should also reflect memory speed.
RAM cooling is becoming more common. Premier RAM manufacturers such as Corsiar, Mushkin, GeIL, Kingston, and OCZ are now shipping sticks with heatspreaders across the chips. Thermaltake sells some RAM cooling kits for sticks without any cooling. The cache is that the heatspreader doesn?t often have much of an effect. TwinMOS makes some of the best overclocking RAM available, and never uses heatspreaders. The effectiveness of the spreaders is a common debate across online forums everywhere.
Many overclocking motherboards offer memory voltage settings. Just like in a CPU overclocking situation, raising memory voltage at higher speeds may aid stability. Some of the higher voltages available can damage the RAM after long exposure, so check with other people who have that RAM to get a feel for its tolerances.
The final element of RAM overclocking is latency. This bit about latency will be short, because a full article is in the works. The short of it is that lower latencies acheive higher bandwidth/performance at a given MHz than higher latencies. However a lower latency setting may not be stable at higher clock speeds, so you may need to use a higher latency. In general, and especially on intel systems, the best combination is very high memory speed, and higher latencies i.e. 225MHz 7-3-3-2. However on some AMD setups the ideal configuration is the highest speed acheivable with a lower latency set i.e. 215MHz @ 6-2-2-2. You should always test both combinations to see which works better on your system. For a quick synthetic test run SANDRA's memory benchmark.
To sum it all up, RAM overclocking is balancing FSB speed, memory ratio, memory voltage, and RAM timings. It takes time and effort, have fun
By W1zzard
Here's a quick table of FSB vs. CPU Frequency vs. Memory frequency with different dividers. Intel
code:
FSB CPU 2.4C CPU 2.6C CPU 2.8C CPU 3.0C Mem 1:1 Mem 3:2 Mem 5:4
200 2400 2600 2800 3000 200 133 160
205 2460 2665 2870 3075 205 137 164
210 2520 2730 2940 3150 210 140 168
215 2580 2795 3010 3225 215 143 172
220 2640 2860 3080 3300 220 147 176
225 2700 2925 3150 3375 225 150 180
230 2760 2990 3220 3450 230 153 184
235 2820 3055 3290 3525 235 157 188
240 2880 3120 3360 3600 240 160 192
245 2940 3185 3430 3675 245 163 196
250 3000 3250 3500 3750 250 167 200
255 3060 3315 3570 3825 255 170 204
260 3120 3380 3640 3900 260 173 208
265 3180 3445 3710 3975 265 177 212
270 3240 3510 3780 4050 270 180 216
275 3300 3575 3850 4125 275 183 220
280 3360 3640 3920 4200 280 187 224
285 3420 3705 3990 4275 285 190 228
290 3480 3770 4060 4350 290 193 232
295 3540 3835 4130 4425 295 197 236
300 3600 3900 4200 4500 300 200 240
305 3660 3965 4270 4575 305 203 244
310 3720 4030 4340 4650 310 207 248
315 3780 4095 4410 4725 315 210 252
320 3840 4160 4480 4800 320 213 256
325 3900 4225 4550 4875 325 217 260
By Supa
Here's another table, this one is more towards AMD systems. No CPU speeds because there are way to many multipliers to cover. Remember that these are all actual MHz, not counting for DDR.
code:
FSBMem 2:1Mem 5:4Mem 1:1Mem 4:5Mem 3:4Mem 2:3Mem 1:2
1005080100120133150200
13366.5106.4133159.6176.89199.5266
14070112140168186.2210280
15075120150180199.5225300
16080128160192212.8240320
16683132.8166199.2220.78249332
17587.5140175210232.75262.5350
18592.5148185222246.05277.5370
19597.5156195234259.35292.5390
200100160200240266300400
205102.5164205246272.65307.5410
210105168210252279.3315420
215107.5172215258285.95322.5430
220110176220264292.6330440
225112.5180225270299.25337.5450
230115184230276305.9345460
235117.5188235282312.55352.5470
I hope this helps
Source:
http://www.ocfaq.com/article.php/overclocking/35
