[GLLUG] RAM Specs

[Chick Tower]

The manual for my motherboard says to use PC1600 or PC2100 DIMMs. 
Crucial's memory finder recommends PC2700 or PC3200 DIMMs.  All RAM 
recommendations are for DDR RAM.  I have some DIMMs given to me by 
someone (Jeff?) over a year ago that I just looked at and they are 
PC2700, but it says they are DDR333.  I doubt they are DDR3, but what 
would DDR333 indicate?  If they were to physically fit properly in the 
two slots on my motherboard, can any damage or instability occur by 
using DDR2, DDR3, or DDR4 RAM when DDR RAM is called for?
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                                Chick