5
Memory Technical
Background
Memory Facts
All new motherboards support SPD (Serial Presence Detect) DIMMs. These DIMMs
have a little EEPROM (memory IC) on the module that allows the BIOS to read the
specifications for the DIMM module.
The BIOS shows the amount and type of SDRAM memory on the bootup screen.
Single-sided DIMMs come in 16, 32, 64,128, 256MB; double-sided come in 32, 64,
128, 256, 512MB.
DIMM Type
The type of buffer and the working voltage of a DIMM module can be read from
the position of the two notches. Please refer to the following diagram for more
information:
SDRAM BUFFER TYPE
Unbuffered
Buffered
RFU
Undefined
3.3V
5.0V
SDRAM VOLTAGE
VCRAM
Virtual Channel RAM is a technology that was initially developed by NEC. VCRAM
increases the memory bus efficiency and performance of the memory module by
providing a set of fast static registers between the memory core and I/O pins, resulting
in reduced data access latency and reduced power consumption. Each data request
from a memory master contains separate and unique characteristics. Multiple requests
from multiple memory masters can cause page trashing and bank conflicts, which
result in low memory bus efficiency. The VCRAM architecture assigns virtual
channels to each memory master. Since virtual channels maintain the individual
characteristics of each memory master request, bus efficiency is dramatically
increased.
