As reported on the EeeUser forum, the EeePC 900 is somewhat picky with RAM upgrades. If the RAM chip is not exactly spec’d like the stock RAM module, then the computer would be prone to freezing, especially when switching between battery and mains power.
And so I tried upgrading my EeePC 900 with a 2GB Kingston memory chip that I currently use on my Compaq B1200. It’s a PC2-5300 CL5 200-pin SODIMM with part number 9905295-052.AH0LF and serial number 900FE501.
I booted up fine on battery power, but when I plugged in the mains adaptor the screen garbled up.
I next tried an Apacer 1GB module with part number CS.01G2A.C00 thinking that it was supposed to be similar (it’s 1GB, after all). The system boots up fine both on battery and mains power. But when you switch from battery to mains, the system just freezes.
And then lastly I tried a Kingston 1GB module with part number 9905295-015.A00LF, and it’s the same with the Apacer chip.
The issue seems to be with running on “high performance mode,” which essentially means at a clock speed of 900 MHz. The EeePC 900 clocks down to 630 MHz when running on battery, to extend battery life. The system then goes back up to 900 MHz when plugged in, so the system is faster. This is with latter BIOS versions. In the earlier BIOS releases, the change is not dynamic. You have to select either power saving or high performance option in the BIOS, and the speed is static at either 630 MHz or 900 MHz.
Note that all of these above RAM modules worked fine on my 701.
Also, note that the RAM module that came with the EeePC 900 is an AData PC2-3200 (running at 400 MHz) with part number DOGC1A08342. I find it strange that the chip is a 400 MHz one. Even the original 512MB chip that came with my EeePC 701 was a 667 MHz one!
This means if you plan to upgrade your 900’s RAM, better make sure the module is compatible!