Does POST check the RAM?

All the while I thought that it's true, and it is but....

Correct me if i'm wrong, POST cannot detect the error when U install a Non-SDR SDRAM to a "SDR only" MOBO. U won't find any error during POST but U will notice that UR RAM is fictitious;
(128 Non-SDR + 256 SDR != 512), until the fatal error, sumthing like "XMS bad" appears during boot-up.

CB-Byte