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Now, I’m rolling out my testbed:
- Intel Pentium 4 2.4C CPU;
- Boxed cooler;
- ASUS P4P800 Deluxe mainboard;
- OCZ PC3700 memory: two modules by 256MB;
- ATI RADEON 9700 PRO graphics card.
So, I installed the processor, set 250MHz FSB and turned the system on. It wouldn’t power up. The problem was simple: when testing Pentium 4 3.0, I made the memory work synchronously with the FSB. This time I forgot to change this setting and wanted the memory to work at 500MHz (250MHz DDR). Although it was PC3700, it wasn’t intended to work at 250MHz and it didn’t. So I browsed through the BIOS Setup and set the memory divisor to 4:5 from the FSB frequency. The i865PE chipset allows such things. In this case, when the FSB frequency is 250MHz, the memory is clocked at 208MHz, which is within its nominal specs. Of course, the system worked all right this time.
I composed a table listing the memory frequencies in systems with i875 and i865 chipsets when the FSB is overclocked:
FSB Frequency | DDR266 (FSB:MEM=3:2) | DDR333 (FSB:MEM=5:4) | DDR400 (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) |
After the system booted up at 250MHz FSB, I started to increase the FSB frequency steadily to find the highest summit our Pentium 4 2.4C could climb. At 275MHz FSB the processor worked without problems and without any additional Vcore increase. Unfortunately, this was all I could squeeze out of the thing. At 276MHz FSB, no voltage increase and no memory frequency reduction could make the CPU pass 3DMark2001. So, the result is:
The processor notched 3.3GHz, and the bus – 1100MHz. What’s important, I achieved this without voltage tweaking. That is, such overclocking is quite safe as far as processor health is concerned. Overclocking without any voltage increase doesn’t reduce the life term of a semiconductor die. As for the memory, its frequency grew to 440MHz with the 4:5 divisor:
Our respect to OCZ and its PC3700 modules, which allowed us to achieve this high result. By the way, we could make the same thing using Low Latency PC3200 modules from Corsair.
Accordingly, the peak bandwidth of the dual-channel memory system in this mode reaches 7.0GB/s, which is astonishingly high. That’s what it gives us in practice:
To our regret, we couldn’t overclock our Pentium 4 2.4C to 3.6GHz as we did with Pentium 4 3.0. Still, 3.3GHz is a good result. This is higher than the frequency of the upcoming top model of the Northwood-based Pentium 4 family. Moreover, I want to say once again that I achieved this using a standard air cooler and without any Vcore increase. In other words, anyone can do the same thing with the help of the most primitive methods, which don’t tell negatively on the system’s health.
