Same problem here i have a P4 2.4 ghz at this moment I'm playing cod4 and Rainbow six las vegas. I'm planning to upgrade to the E2140 but according to cod4 minimum requirements the E2140 is to slow but my cpu just reached the minimum. Does this mean my old P4 chip out pace the E2140 at stock speeds ?
The E2140 is much faster than a P4, the E2140 is a budget processor and should play COD 4 easily as long as the rest of your hardware such as graphics card and memory is sufficient. The E1240 is known for it's overclocking properties, but this is only true with a decent motherboard. Personally for longevity I'd get a E4500 processor (or Q6600 for a quad setup). What graphics card are you running as it would influence COD's playability more than the processor?
I have a 2.2GHz P4 with a FSB of 400Mhz and 512KB Cache
Would a Celeron D 2.8GHz with a FSB of 533Mhz and 256KB Cache give me an increase of performance?
I haven't seen any official benchmarks, but I doubt it would make much difference in terms of frame rates as both processors are below the minimum standard for today's gaming. Your better of getting a better graphics card such as the 3850, 3870, 8800GS, 9600 GT, or 8800GT. But even with the best graphics card your slow processor and limited ram would be a bottleneck. I recommend finding the cheapest motherboard with AGP and PCIx slots and use your x1650 card until you can afford a better card. Meanwhile get the cheapest dual core processor you can afford such as E1240 or E1280 (recommended E4500 or better) as they can play COD4 easily.