dual channel 512's mb vs. 1.5 gig

I have a toshiba m65-s809 it supports dual channel memory, I am new to the laptop arena and haven't built a computer in over 5 years.
I have the m740 centrino processor in it.
Scenario:
2 sticks of 512 ddr2 soddim 533mhz 4200 = 1 gig dual
VS.
1 stick of 512 ddr2 soddim 533mhz 4200 and 1 stick of 1 gig ddr2 soddim 533mhz 4200 = 1.5gig single

which one is going to be faster for photoshop and other multiple applications running?

I have heard that the dual does twice the work twice. I don't mean to sound ignorant, it's just been awhile.

 

dual channel doesn't do twice the work. it provides a small performance gain when you are running 2 sticks of the same size ram at the same bus speed.

if the choice is between 1 GB and 1.5 GBs, i would go with 1.5 GBs regardless of bus speed.

 

Why?
with dual does the board read it as 1 gig?
I've read (not in awhile though) that dual is faster for graphics application and multitasking. Is there any truth to it?
If infact dual isn't that great, then whats the hype to run dual instead of old school of just adding more ram?
I just ordered 2 sticks of the 512 to run dual this came per a couple of buddies at differen't comp. service and repair centers.
They give me cost so profit isn't the moative, any idea or experience would help.
Thanks and I did search the forums first for the answers, didn't find anything pertaining to why.

 

This is how dual-channel memory works -

Think of a channel as a 'door'. If a RAM has one door (single channel), that means that there's one way into the RAM and one way out - through the same door. Only one program can access the RAM at one time. However, if you have two doors (dual channel), then there are two ways in and out of the memory, and programs can access data they have stored in the RAM easier and faster. Dual channel reduces bottlenecks. You'll see a slight performance increase in games, rendering, and benchmarks.

 

would it have been faster to just add a 1 gig to help out the 512mb

 

More ram would be better, yea.

Dual channel is neglible, and the 1.5gb ram would probraly be faster then the 512 x2. Not to mention upgrading, if ever necessary will just require you to buy one 1gb stick and take one 512mb off not two 512mb modules

 

well atleast is samsung ram any good?

 

A faster hard drive will give a bigger perfromance boost.

 

Yeah but they want $400 for one from Toshiba, memory is quita bit cheaper.
Any idea on if in fact they are replaceable and after market drives are cheaper and excelent quality. 60g 7200 rpm is about right, all my files are saved on disc for storage instead of my hard drive.