How can I tell on openSUSE 11.1 64bit whether the RAM on my notebook is in dual channel mode?
I just installed another 2GB, and the BIOS correctly detects a total of 4GB. Yet it does not tell me anything about the mode. I could not find the info with hwinfo either.
if both banks have 2 GB RAM modules then it should be set as dual-channel. I don’t know of any Linux tool that will tell you if it’s dual or not. On my machines, during POST, the BIOS reports if my RAM is running as dual or not
Wow, that was a quick reply. 
Well, this notebook BIOS stuff shows nothing during boot. It’s just the logo and then grub.
Just tell us what hardware you have got there and we will tell you if you got dual channel mode
there should be an option to disable the logo in the bios. one of my asus mobos also by default displays a logo but after disabling it, I get standard POST messages
I have a R61 Lenovo notebook. That is SantaRosa chipset.
Dual-channel is a hardware specific option; the operating system has little bearing control on this. Nearly all laptops that support 4GBs of RAM probably have dual-channel capabilites.
Many times there will be an option at the laptop boot logo to view more information by pressing a button (eg. tab, esc).
I would also look in the BIOS for a system information option; this would probably say if you were running dual-channel or not.
Alternatively, if you look in the BIOS for a setting such as “Display logo”, disable/enabling this option would allow you to view the system information as the laptop goes through POST. This is where it would tell you if you’re running dual-channel or not.
All in all, virtually all hardware has dual-channel option. If the ram sticks are the same then it is dead sure.
Dead sure sounds good.
Now I found a switch ‘diagnostic’ for boot. It shows a lot of info, but nothing about the memory mode.
The next problem is, that since I checked it, I am not able to enter the BIOS setup any more . The screen will just show lots of random pixels, 
If i am not wrong then memtest would tell you if you run in dual-channel mode
Yes, memtest86+ did the trick.
It is in dual channel mode, Thanks a lot!
Now I’ll have a closer look at that BIOS…
The following is very off topic:
Just a comment to somebody who can’t enter the BIOS setup of his thinkpad and stumbles upon this thread.
Upon pressing the blue thinkvantage button during boot a timer should show up, and you may press F1 to enter setup. If you are in diagnostic mode, and see only random pixels instead of a timer, F1 still works. (At least it worked for me.)
Thanks again to all who helped me with my question.