Grub editing

Since some days I have an error at the address 209.3 from my 256 memory chip. Before running to the computer shop in order to get me a new chip I know that I can reduce the memory use at bootup by just adding mem=209MB. In lilo I had experience in the past that this info could be added in the append line. For Grub I have no idea where to include it. Just adding it in the line for the SuSE boot does not take effect. Somebody knows where to include the info?