Added more RAM and System slowed down

I have a pentium 4 3.0Ghz HT based system with intel 915GAV motherboard.
I had 1 gb of memory 2X512 running in dual channel mode( in slot A-0 and Slot B-0) now i have added one single 1gb module in slot A-1, and I dont c any performance difference and also my dual channel mode isnt on now, plus the boot time for Windows XP has increased, can someone advice some solution PLease !

 

Dual channel only works with configurations like this:

DIMM 1: [======] - One RAM Module
DIMM 2:
DIMM 3: [======] - One RAM Module
DIMM 4:

--------------------------------

DIMM 1:
DIMM 2: [======] - One RAM Module
DIMM 3:
DIMM 4: [======] - One RAM Module

--------------------------------

DIMM 1: [======] - One RAM Module
DIMM 2: [======] - One RAM Module
DIMM 3: [======] - One RAM Module
DIMM 4: [======] - One RAM Module

Each RAM module must be the same size for dual channel I believe, but you must have an even number of modules for dual channel to work.

 

Yeah, its sounds like its going to be running as single channel. You've halved your bandwidth.

 

But now the RAM is 2gb so should it be slower than 1 gb(512X2) in dual channel mode.

 

Having more RAM doesn't mean the system will run faster, you've now got more RAM but the RAM is running in single channel mode and therefore running slower than 1GB in dual channel mode.l

Aso what speeds are the RAM modules?

If your old RAM was PC3200 and your new RAM was PC2700 for instance the old RAM will be forced to run at the slower speed.

Just to let you know.

 

All my RAM modules are PC3200, and tell me like there were 2 512mb identical cards running in dual channel mode, and now if I put one identical card of 1gb for the 1 gb I ve already put, like 2X512mb and 2X1gb, will then dual channel mode be enabled back.

 

you need a pair, or 2 pairs of ram for dual channel.

 

I tried putting the 3 ram modules in following way :

DIMM 1: [==512==] - One RAM Module
DIMM 2: [==512==] - One RAM Module
DIMM 3: [==1GB==] - One RAM Module
DIMM 4: - Empty

And now my system says Dual Channel Mode on.
Can U explaing this that how dual channel mode switched on.

 

Dual-channel functionality requires the same amount of RAM in each channel.

 

If you run a RAM bandwidth benchmark you will probably see its below 3200mb/s. DDR400 in dual channel will in most cases exceed 3200mb/s.

 

Also, adding more RAM won't net you a boost unless you're doing something that will benefit from it.