Bear in mind that with the Winchester chips its hit and miss as to whether you get a good overclocking CPU or not, depending on the week they were manufactured each chip varies in performance of its overclocking capability.
I had a 3200+ Winchester which i could not overclock past 2.4Ghz stable (from 2.0Ghz), i built a machine for a friend who just wants to play games, but isnt into overclocking or IT really.. anyhow i gave him my CPU at stock speeds and received his a week 47 Winchester 3200+ i could overclock this to 2.6GHz, however i could only keep it at 2.6GHz stable on a 1.6Vcore (from 1.4V) if i left F@H running for 18 hours or so i'd end up with a CPU temperature nearing 60C which i'm not comfortable with.
I like my CPU temperatures to stay below 50C, to test this out i stick the heating in my room on once i find a stable OC to max (warms room to about 35C) then i start seeing the highest temperatures.
Also remember that you will need a new HeatSink & Fan.
But again, you DO NOT need to overclock a AMD Athlon or AMD XP @ 1.8Ghz (Barton or 2800+) would still play Doom3 with out any problems.
If you are experiencing low fps, or lower fps than you think you should be getting it is down to other components, such as memory size/speed and timings or graphics card, or drivers.
Your 1.8GHz is fine for Doom3, you'll see a performance boost of 10FPS max if you overclock by 800Mhz, and bare in mind you'd need either: GeIL Ultra-X / Corsair XL PC3200 2-2-2-5 memory to gain those speeds, or PC4400 memory (DDR550).
If you want to give it ago anyway:
Increase the FSB in increments of 5 Mhz at a time - test it for stability (run 3Dmark03 / 3Dmark01 / F@H / Prime95), then reboot up it again.. until it becomes unstable in one of these programs, then increase your Vcore by 0.025 volts, until it becomes stable.
Once you start overclocking your memory i would stick your memory at 2.8VDimm, to ensure max performance).
You will need to lower your HTT (LDT) on the motherboard options as well, as this is the HyperTransport speed (1GHz = Memory Speed (FSB) x HTT)
HTT can be set @ x1, x2, x3, x4 & x5
by default its set to x5 as on AMD64's the memory runs @ 200Mhz FSB
200Mhz FSB (memory speed) x5 = 1000MHz (1GHz hyper transport)
You can keep HTT @ x5 up until about 220Mhz FSB, then it will become unstable after that and you need to decrease the HTT to x4.
Remember that its not JUST about CPU speed, if you have a 2.4GHz overclock on your 1.8GHz AMD64 3000+ it's no good if your memory timings are running @ CAS 3-4-4-8 2T Command
Memory Timings are basically the "clocks" that certain parts of the memory take to transfer data to other parts of the memory (this effects the overall speed of the memory).
2-2-2-5 is the the tightest factory timings in the industry at the moment mainly available for PC3200 memory such as: Corsair XL range / Geil Ultra-X range / GSkill PC3200-PC4800 (only runs 2-2-2-5 @ PC3200) / OCZ Gold Range
I had PC4400 but it was only worth me running an overclock if i could reach 2.5GHz as my memory timings kept having to be loosened.. @ 2.5GHz i was running @ 2.5-5-5-9
obviously you can also run a memory divider (DDR333 or 2:1 CPU:FSB ratio)
if you don't understand any of this then you really shouldn't overclock until you've read alot on understanding it: [google]AMD64 Overclocking Guide[/google]
