Acorp 5VIA73 Manual page 16

The Dual Inline Memory Module (DIMM) memory module must
be 3.3v Extended Data Output (EDO) DRAM or SDRAM. You can
identify the type of DIMM module by the illustration below:
RFU Unbuffered 5.0V Reserved
Buffered 3.3V
Voltage Key Position
DRAM Key Position
168 Pin DRAM DIMM Notch Key Definitions
The notch on the DIMM module will shift between left, center, or
right to identify the type and also to prevent the wrong type to be
inserted into the DIMM slot on the Mainboard. You must ask your
retailer for Specifications before purchasing.
Four clock signals are supported on this mainboard
16 / Chapter 3 Installation