CPU Overclocking

Our testbed was built with the following components:

• ASRock 4Core1600P35-WiFi+ mainboard, ver. 1.03, BIOS P1.30;
• NVIDIA GeForce 8800 GTS 320MB graphics card;
• Seagate Barracuda 7200.10 HDD, ST3320620AS, 7200 RPM, 16MB, SATA 320GB;
• Zalman CNPS9700 LED CPU cooler;
• Antec NeoPower HE 550 PSU (550W).

ASRock 4Core1600P35-WiFi+ can work with DDR2 or DDR3 SDRAM. We started our tests with DDR2 SDRAM and used familiar Corsair Dominator TWIN2X2048-9136C5D memory modules (2 x 1024MB). For our experiments we took Intel Core 2 Duo E8400 (3.0GHz, FSB 333MHz, 6MB, Wolfdale, rev. C0) that can work at 450-455MHz FSB, i.e. can overclock beyond 4GHz frequency. The memory frequency was set to the minimum and its voltage was increased to 2.1V. Processor Vcore was set to 1.55V, NB Core Voltage and VTT Voltage were set to High. Our preliminary tests showed that Middle setting was not enough to overclock even to 400MHz FSB. Of course, the North Bridge chipset heatsink did heat up a lot in this case, so we had to use an additional quiet 80mm fan.

ASRock 4Core1600P35-WiFi+ mainboard started at 445MHz FSB. At 440MHz it booted Windows OS, and it could run stably only at 420MHz FSB. We reduced the processor Vcore to 1.45V, while the memory worked at 840MHz frequency with 4-4-4-12 timings or at 1008MHz frequency with 5-5-5-18 timings.

It is indeed a very modest result for a mainboard built around a chipset that would normally conquer frequencies about 100MHz FSB higher. However, we could immediately answer the question “what maximum FSB frequency does ASRock 4Core1600P35-WiFi+ support?” At first we thought that we would never find out this frequency because the mainboard cannot lower the processor clock frequency multiplier, but it didn’t matter for 420MHz FSB.

I would like to point out specifically that during our experiments the mainboard would occasionally freeze on boot-up or would not start at all. However, Boot Failure Guard technology worked impeccably, so we didn’t use the Clear CMOS jumper even once. It was a little annoying that we had to use up all three boot-up attempts before the mainboard would start in safe mode. However, all the previously selected BIOS settings remain intact, which is extremely important because the mainboard doesn’t allow saving settings profiles.

We pinned some hopes upon the DDR3 SDRAM, however, this part of our test session ended up in a total fiasco. At first we worked with 2 x 1024MB Super Talent W1600UX2G7, then we replaced it with a pair of OCZ PC3-14400 Platinum Series (OCZ3P18002GK) modules, but it didn’t make any difference. At 420MHz FSB ASRock 4Core1600P35-WiFi+ mainboard started only when the memory was working at the minimal possible frequency of 400MHz, as DDR3 800. And taking into account overclocking, the actual memory working frequency equaled about 1GHz, which is pretty good for DDR2, but is indeed too low for DDR3.

The only way for DDR3 to outperform the predecessor is to reach the frequencies .5 times higher. It is quite possible, contemporary DDR3 SDRAM modules can do things like that, but only not on an ASRock 4Core1600P35-WiFi+ mainboard. When we set the memory as DDR3 1066 or DDR3 1333 during our processor overclocking experiments, the mainboard wouldn’t even start. These dividers are formally quite operational, as the mainboard did start with DDR3 1333 memory setting when the CPU was working at its nominal speed. Although I have to admit that the timings looked pretty strange in this case: 7-9-9-24. Besides, the Performance Level was set differently for each channel: 6 for one and 7 for another.

It is impossible to correct the timings and set at least the default ones for OCZ PC3-14400 Platinum Series (8-8-8-24). As you remember, the BIOS of ASRock 4Core1600P35-WiFi+ mainboard allows setting reasonable timings only for DDR2 SDRAM. As soon as we switch to DDR3, only the DRAM CAS# Latency interval shifts so that we can choose from the interval between 5 and 9. All other timing settings remain the same as with DDR2, although they are too low for DDR3 SDRAM. We tried changing only DRAM CAS# Latency and leaving the other timings in Auto, as we hoped that the mainboard would choose the most optimal setting on its own, but it didn’t help. The mainboard still wouldn’t boot with the memory set as DDR3 1066 or DDR3 1333 if the CPU was overclocked to 420MHz FSB.

So, we see that during processor overclocking DDR3 memory can only work at extremely low maximum frequency of 1GHz. Taking into account that DDR2 can easily hit this speed with lower timings, there will be absolutely no intrigue in comparison between the two. A system built on ASRock 4Core1600P35-WiFi+ mainboard and DDR3 SDRAM will be too slow and hence unable to compete against any other overclocker platform. You can improve the performance by simply replacing DDR3 with DDR2 SDRAM. Unfortunately, we have to admit that ASRock 4Core1600P35-WiFi+ mainboard only formally supports DDR3 SDRAM. Using this memory type on this platform is not justified: neither from the economical, nor from the performance standpoint.

Our attempt to overclock Intel Core 2 Duo E6300 (1.86GHz, FSB 266MHz, 2MB, Conroe-2M, rev. B2) also failed. If you look at the table above showing the supported memory frequencies and their dependence on the nominal FSB speed, you will notice that DDR2 can work at the minimal frequency of 333MHz, i.e. as DDR2 667. CPUs with the nominal 333 (1333) MHz FSB, such as Intl Core 2 Duo E8400, have a 1:1 divider for that. During overclocking and FSB frequency increase, memory frequency grows synchronously and everything goes on smoothly. However, processors with 266MHz FSB, such as Intel Core 2 Duo E6300, use an increasing divider of 4:5 to set the same 333MHz memory frequency. It means that during overclocking every 4MHz of the bus frequency increase correspond to 5MHz memory frequency increase. Therefore, it is quite possible that the CPU overclocking will end up limited by the memory modules potential.

Suppose that memory can run stably as DDR2 1100 at 550MHz frequency. You can easily calculate that the maximum bus speed in this case will be only 440MHz, although our Intel Core 2 Duo E6300 processor sample can overclock to 490MHz FSB. So, even theoretically, we will not be able to overclock our processor to its maximum on ASRock 4Core1600P35-WiFi+ mainboard. In reality things got much worse. Even at 410MHz FSB the system wouldn’t run stably, and since the board doesn’t work well with DDR3 at all, switching to a different memory type didn’t help, either.

Overclocking processors with 200 (800) MHz FSB is an even bigger disaster. The minimal DDR2 mode for them is again DDR2 667, i.e. they use a lowering divider of 3:5. Every 3MHz of the FSB frequency result in a 5MHz memory frequency increase. Our assumption turned out wrong: DDR2 memory can only work in ASRock 4Core1600P35-WiFi+ mainboard at frequencies slightly beyond 500MHz, i.e. when we overclock processors with 200 (800) MHz FSB we will hardly be able to push the FSB speed past 300MHz.

There is only one advantage in all these overclocking mishaps: new processors keep coming out and their nominal frequencies keep growing. Old CPUs get discontinued and new ones are sold at the same prices. If we are talking about processors with 200 (800) MHz FSB, their wholesale price is $113 and $133, and their retail price is very close to that, too. And 300MHz FSB frequency will be more than enough for efficient overclocking of the top Intel Core 2 Duo E4600 (2.4GHz) and recently announced but already widely available Intel Core 2 Duo E4700 (2.6GHz).

Although I have to admit that the situation is pretty strange overall: we can’t quite figure out the positioning of ASRock 4Core1600P35-WiFi+ mainboard in the market. An inexpensive mainboard like that is usually paired with an inexpensive CPU. I our case these will be processors with 200 (800) MHz and 266 (1066) MHz bus. However, ASRock 4Core1600P35-WiFi+ is least suitable for overclocking of these particular processors, and copes best of all with relatively expensive CPUs supporting 333 (1333) MHz FSB. In fact, “copes best of all” is also an exaggeration: the board doesn’t do such a good job here, too, as we have just shown you.