Presence Detect Chip - SPD - More than one DIMM

[KAWill70]

How does the Motherboard or BIOS handle the Memory SPD Presence Detect information when more than one memory module is inserted into a Motherboard?

Assume the information might be different from each DIMM.

Does the Motherboard read speed information from only one socket, or does it read all sockets and set things up for the slowest DIMM?

Or are some Motherboards able to assign different timing to each DIMM?

I know that one should in general not mix memory of different characteristics. I'm just curious what the Motherboard does with speed information from multiple DIMMs.

 

[GhislainG]

It reads SPD info from all modules and then uses the slowest settings. However installing modules that require a different voltage would cause stability issues unless the highest voltage is used (has to be set manually).

 

[KAWill70]

Thanks for the reply. I hadn't thought about the DRAM voltage issues although I don't think that applies to my case using a lower end system built in 2005.

One wonders if all Motherboards have a BIOS that truly utilizes all SPD information from all memory sockets. I'd guess that size information may be required from all sockets, but I really wonder about the speed information.

That could explain why many people have trouble when mixing DIMMs of different brands or speeds.

Perhaps Motherboards today have done a better job with memory configuration and setup. It's also possible that the higher end Motherboards do a better job.

If memory timing is strictly a BIOS function perhaps one could research that area and learn more.

 

[KAWill70]

Best answer selected by KAWill70.