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Overclocking Pentium 4 Processors and Overclocker Memory

Besides ordinary DDR400 SDRAM (often marked as PC3200), many manufacturers offer faster modules like DDR433 (PC3500), DDR466 (PC3700) or even DDR500 (PC4000). JEDEC, however, did not standardize any DDR SDRAM with a frequency above 400MHz. Anyway, many memory manufacturers learned to design memory chips supporting higher working frequencies than the standard 400MHz. It is exactly for the modules built of such chips that they use “DDR500” marking and the like.

The second part of this review is dedicated to these particular memory modules capable of working at more than 400MHz and their advantages, if there are any. The currently available dual-channel chipsets from the i875 and i865 families for the Pentium 4 processor do not provide any multipliers to increase the memory frequency. It means that you may need your memory to go faster than the regular DDR400 SDRAM only when you are up to some exciting CPU overclocking by means of increasing the FSB speed above the nominal 200MHz. On the other hand, i875 and i865 do provide diminishing coefficients (divisors) of 5:4 and 3:2, so you do not actually have to use an overclocker memory with an overclocked FSB. All in all, you have three options:

FSB frequency

Memory frequency

FSB:MEM=3:2

FSB:MEM=5:4

FSB:MEM=1:1

200 MHz

133 MHz (DDR266)

160 MHz (DDR320)

200 MHz (DDR400)

210 MHz

140 MHz (DDR280)

168 MHz (DDR336)

210 MHz (DDR420)

220 MHz

147 MHz (DDR293)

176 MHz (DDR352)

220 MHz (DDR440)

230 MHz

153 MHz (DDR306)

184 MHz (DDR368)

230 MHz (DDR460)

240 MHz

160 MHz (DDR320)

192 MHz (DDR384)

240 MHz (DDR480)

250 MHz

167 MHz (DDR333)

200 MHz (DDR400)

250 MHz (DDR500)

260 MHz

173 MHz (DDR346)

208 MHz (DDR416)

260 MHz (DDR520)

270 MHz

180 MHz (DDR360)

216 MHz (DDR432)

270 MHz (DDR540)

280 MHz

187 MHz (DDR373)

224 MHz (DDR448)

280 MHz (DDR560)

290 MHz

193 MHz (DDR386)

232 MHz (DDR464)

290 MHz (DDR580)

300 MHz

200 MHz (DDR400)

240 MHz (DDR480)

300 MHz (DDR600)

The first conclusion that comes to mind when we look at these results implies that using memory in synchronous mode with the overclocked FSB may bring some performance advantages. However, this may not be quite true. As we have already seen, memory timings play an important part in determining the overall performance of an i875/i865-based platform. And the overclocker memory  working at higher frequencies cannot boast aggressive timings. Moreover, the production technology of memory chips is such that chips intended for work with aggressive timings at 400MHz just cannot achieve (even if we use poor timings) the frequencies of overclocker chips, although the latter have weaker timings at 400MHz. For example, we have not yet encountered DDR500 modules that would work with 2-2-2-5 settings at 400MHz. On the other hand, however high-quality it may be, a DDR400 module cannot work stably at 500MHz, although it uses the most aggressive timings at 400MHz.

Thus, the overclocker is confronted with a problem, which of the two options to choose: overclocker memory with relatively poor timings, but working synchronously with the FSB, or a lower-frequency memory with aggressive timings, which requires a diminishing coefficient.

To carry out our test, we used a Pentium 4 2.4C processor that had been very good during overclocking (see our Intel Pentium 4 2.4C Overclocking article). We tested this CPU with the FSB sped increased up to 250MHz. In this mode, this CPU with a fixed multiplier (12x) works at 3GHz, while the overclocked FSB allows using memory at 250MHz (500MHz DDR), 200MHz (400MHz DDR) and 167MHz (333MHz).

 
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