Which ram to buy? 533 or 667?

667 fsb for a C2D sounds a bit low.
IF its correct, and u dont OC, that all important 1:1 ratio would require 333Mhz ram

Ie:
667FSB is quad pumped, so 667/4=166Mhz
Ram is double pumped, so 533/2=266Mhz

IF, IF all those assumptions are correct for a laptop, 333Mhz ram would be fine, but u prob cant get that so 533 is good too.

Dont wry too much abt timings either.

The OP was talking about a Core2 mobile, the initial Core2's for laptops did have a 667FSB. It's only in the desktop where Core2's start from 800MHz (Allendale) or 1066MHz (Conroe). Only the recent update to mobile Core 2's did 800MHz FSB's started to appear for the mobile.

And I would agree, get the 667 if you really want a 1:1 FSB:RAM ratio. The RAM latency is something secondary and you shouldn't worry about it.

The basic answer for your laptop is that any of your RAM choices are quite fast compared with the CPU's FSB, as long as you have a pair of the same size modules installed, so you are running in dual channel mode. If not running in dual channel mode, be sure to get the DDR2-667 speed, in order to keep up with the 667MHz FSB data rate.

Thanks alot guys. Ill go with the 667, both are same price almost anyway so why not the 667. Now i can rest my mind  .
One last Q, kingston or Corsair? Both are the same specs, so anyone better than the other for the 667 ddr2 ram? thanks again

Sorry... dont know if im missing something, or if anyone actually read my post  

Assuming the Mobile works the same as the desktop

CPU fsb is quad pumped
RAM is double pumped
Therefore to maintain a 1:1 ratio with a 667Mhz FSB u will need 333Mhz ram.

(As an 'idiots guide to Intel' your ram should always be half the speed of ur fsb if u dont OC)

667Mhz ram will achieve a 1:2 ratio (cpu:ram). Essentially the ram is working at twice the rate of the cpu. This wont make your system slower, but it wont be any faster either, it just has to wait.

@ mrmez

I saw what you said earlier. And that did make a lot of sense. Since there is no added improvement with 667, i was mainly concerned about the ram latency as the 667 was a bit higher than the 533 in this regard. But since the difference of latency between the 667 and 533 isnt much or noticeble, and as price is almost same (533 is a tiny bit more expensive), so that is why then i guess i would go for the 667. And besides, in future maybe the 667 may come in handy with another system where i can achieve the 1:1 ratio. Thanks for your help  .
oh um, kingston or corsair? what do you say?

Last I heard, Corsairs are tuned more to performance than compatibility, so it should work on a lot but not all boards. And kingston's are tuned to compatibility with some minor cost to performance, so kingstons should work on 90% or more of boards with a minor performance hit. Though we are talking of the performance difference of around only 0 or 1 fps in games and 2 seconds or less gain in productivity software which is a very very small amount.

You could try the corsair first or at least check if it could possibly compatible with your laptop. If it ain't compatible, kingstons are always there to save you.

Kingstons, even their value line, are pretty good. Corsair's premium lines are good, but they contract out their ValueSelect line to the lowest bidder, so stay away from that.

The 667 and 533 chips have 5 and 4 CL respectivly

They're almost identical in performance because of that.

Thanks guys, you really have been a great help, really appreciate it. Why couldnt they make computer technology simple lol.
I have been searching for kingston and corsair rams (that ship to or within australia). In corsair i can only find value select ram (which is a bit cheaper than the value line from kingston). As you mentioned Mondoman, that valueselect corsair arnt that good, so i guess i wont go for that.

In kingston, well there are for sure value line, average price of about $70(australian dollar), for 1gb 667 ddr2 ram. ->part no. KVR667D2S5-1G

There is also a dell inspiron 6400 notebook specific ram (same specs) for the price of about $130 (average). -> part no. KTD-INSP6000B/1G

Is there really a performance difference between these both, or quality difference? To me, it seems just a marketing strategy to label the same ram as dell specific ram, and thus to hike up the price.
any feedback on this? thanks alot

Actually the 1:1 ratio would be DDR-333. Both it and the mobile 667 bus run at 166MHz. Data rate woud be 1:1 as well, so long as the system supports dual-channel mode.