Mixing ram on a PC100 motherboard

I recently installed 64 megs of ram on a PC100 motherboard. The original ram is SDRAM in an eight chip configuration. The new ram is in a four chip configuration and when the machine boots it is telling me that it is NVRAM, it used to say SDRAM in DIMM slot 1 now it says NVRAM DIMM slot 1,2. The new ram is 133 mhz whereas the old is 100 mhz. The machine seems to be working fine. What is this strange Message ? ( NVRAM )