T60 Memory 5300 vs 4200 DDR2

[bfgun]

My machine currently has a 1 gb ddr2 5300 memory stick, i found a 1gb ddr2 4200 stick that some sites say it's backwards compatiable. The processor on my laptop is a 1.83 intel duo core (not the duo core 2) Wanted to see if the 4200 stick will work, without any performance hit or will the machine run at the 4200 speed forcing the already installed 5300 stick to run a bit slower.

Will i see a performance hit on this or should i just go ahead with a second 5300 ddr2 stick?

Thanks!
B

[ryengineer]

The machine will run at 4200 (533Mhz) memory speed.

[bfgun]

the question is - are the 5300 sticks actually too high in terms of speed for default settings on a t60?

I know it'll run at 5300, but i think the 5300 sticks run at a higher speed if the system will support it.

anyone?