Developer Manual/RAM init

One of the most important tasks of coreboot is to initialize your system RAM.

SDRAM

There are a number of steps you have to perform to properly initialize SDRAM. This depends on the chipset, as well as the DIMMs which are inserted into the mainboard (and their properties, such as CAS latencies, and so on).

Sample northbridge datasheets:

• http://support.intel.com/design/chipsets/810/
• http://support.intel.com/design/chipsets/datashts/290656.htm
• http://download.intel.com/design/chipsets/datashts/29065602.pdf

Sample SDRAM datasheets:

• http://www.micron.com/products/partdetail?part=MT48LC16M16A2BG-75
• http://download.micron.com/pdf/datasheets/dram/sdram/256MSDRAM.pdf

Resources

SDRAM:

• Intel SPD Standard
• Micron 512 MB SDRAM Datasheet (PDF) -- contains some helpful explanations

DDR SDRAM:

• JEDEC DDR SPD Standard (PDF)
• Understanding DDR Serial Presence Detect (SPD) Table
• Micron DDR400 Datasheet

DDR2 SDRAM

• JEDEC DDR2 Standard (PDF)
• JEDEC DDR2 SPD Standard (PDF)
• DDR2 DIMM SPD Definition

DDR3 SDRAM

• Understanding DDR3 Serial Presence Detect (SPD) Table

Note: Micron lists SPD values for all the memory they produce. This really helps when trying to trouble shoot memory and SPD values. Micron SPD Lookup