|See response 2 in this - try cleaning the contacts on the ram modules, and making sure the modules are properly seated:|
Some ram manufacturer's modules do not strictly adhere to the JEDEC standards that most mboards bioses use to determine ram settings.
In that case, the ram settings in the bios Setup that the bios has automatically chosen may not be correct.
Check the ram settings in your bios - the ram voltage, and the ram timing numbers - those should be the same as for the specs for the modules themselves. Often the ram voltage and timing numbers are printed on the label on the modules.
If the voltage setting or timings settings in the bios are different from the specs for the ram, change them in the bios. The timing numbers must be as close as you can get to the same, or slower timings (higher numbers = slower) - you won't notice the difference the slower settings make.
If you have a mix of different modules
- don't mix ram that different voltages are specified for - the bios will force the ram to use the lowest voltage, if "by spd" or similar is used (default settings) - ram that a higher voltage is specified for is more likely to not work properly in that situation.
- the bios settings must be those for the slowest timing settings of all the modules, or slower (higher numbers = slower).
If you DO have a mix of modules that require different voltages, you may or may not be able to tweak the ram voltage the bios is using to a higher value such that all the ram will work fine, but you can't exceed the fractional + or - voltage tolerances for the modules.
The fractional + or - voltage tolerances for the modules can be hard to determine - e.g. Kingston has that info readily available for most of their modules, but many other ram manufacturers do not.