Multiplier + FSB is an even better way to overclock

So you have a 800MHz processor that hits 1GHz, but what’s better than running at 100MHz x 10.0? You guessed it, running at 133MHz x 7.5. Both settings yield a 1GHz overclock, however with the latter you are running your FSB at a 33% higher frequency, not to mention your memory bus now runs at a 33% higher frequency as well. This translates into 1/3 more memory and system bus bandwidth allowing you to make much more out of your overclocked CPU than before.

Since we are doing all of this overclocking on an AMD 760 platform with DDR SDRAM, if you want to try it you're going to want to make sure that your DDR SDRAM can run at PC2100 speeds (133MHz DDR) otherwise you'll definitely run into some problems.

There are a couple of sweet spots when dealing with Multiplier + FSB overclocking, the two we will talk about in particular involve the 7.5x multiplier and the 133MHz FSB.

Perfect Overclockers
CPU
FSB Frequency
Clock Multiplier
Athlon 750MHz
100MHz
7.5x
Duron 750MHz
100MHz
7.5x

AMD currently has 1GHz Athlons available, and we have already seen Durons overclocking to 1GHz levels and sometimes beyond that, so it makes sense that an overclock to 1GHz is pretty reasonable. The two chips that were made for this overclock are the Athlon 750 and the Duron 750. Why? Because they both have a 7.5x hard coded multiplier, and simply switching to the 133MHz FSB will yield a 1GHz clock speed, provided that your CPUs can handle it.

If they can't, you can just as easily drop the clock multiplier to 7.0x or 6.5x while keeping the 133MHz FSB. And as you're about to see, the 133MHz FSB is definitely worth it over a small clock speed drop if necessary.

Let's take a look at the currently available Athlon and Duron CPUs, their clock multipliers, and see which speeds we should aim for in general with this type of overclocking.

Overclocking Possibilities
CPU
Clock Multiplier
Original
(100MHz FSB)
Clock Speed
Overclocked (133MHz FSB) Clock Speed
Athlon 650MHz
6.5x
600MHz
866MHz
Athlon 700MHz
7.0x
700MHz
933MHz
Athlon 750MHz
7.5x
750MHz
1GHz
Athlon 800MHz
8.0x
800MHz
1.07GHz
Athlon 850MHz
8.5x
850MHz
1.13GHz
Athlon 900MHz
9.0x
900MHz
1.2GHz
Athlon 950MHz
9.5x
950MHz
1.26GHz
Athlon 1GHz
10.0x
1GHz
1.33GHz
Athlon 1.1GHz
11.0x
1.1GHz
1.46GHz
Athlon 1.2GHz
12.0x
1.2GHz
1.6GHz
Duron 600MHz
6.0x
600MHz
800MHz
Duron 650MHz
6.5x
650MHz
866MHz
Duron 700MHz
7.0x
700MHz
933MHz
Duron 750MHz
7.5x
750MHz
1GHz
Duron 800MHz
8.0x
800MHz
1.07GHz

The numbers in Red are the ones that aren't too realistic expectations, not with conventional cooling or based on AMD's current yields. The bold numbers in the last column, however, are fairly reasonable goals to shoot for. And using the multiplier adjustment techniques we discussed earlier, if you have a Duron 800 for example and aren't able to hit 8.0 x 133MHz, then you can simply decrease your multiplier (assuming you have a board capable of doing that) to 7.5x or 7.0x and still maintain a good speed increase.

As we mentioned earlier, the two CPUs we'll be focusing on will be the Athlon 750 and more importantly the Duron 750. Why do we saw more importantly? Well, the Duron 750 currently sells for $90 - $100 boxed, or $70 - $80 for OEM parts. Not too bad for something that has the potential to run at 1GHz.

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