What are the differences between these 2 RAM modules:
- Certified by JEDEC at 3200MT/s data rate as described here. (Actually I have never seen one)
- JEDEC certified at 2133MT/s but has an XMP profile to run at 3200MT/s 1.2V
The only difference which I have been observing so far is that enabling XMP not only does it change the timing and data rate, but it also increases my memory controller voltage from 0.85V to 0.95V automatically (Ryzen 1400 SOC voltage).
Assume that no voltage changes are needed to run the RAM module at XMP data rate, is XMP the same as JEDEC in this case? If it is, then why do we need XMP anyway?
1 Answer
To clarify the terms:
JEDEC is the organization that publishes the standards for memory technologies. Your linklists the standards by JEDEC for DDR4 modules, starting from the DDR4-1600J standard. In some cases people use JEDEC to refer to a set of predetermined memory speed settings that can be applied in BIOS, but this is wrong.
This JEDEC standard is calledExtreme Memory Profile (XMP)and it denotes the set of profiles that the RAM manufacturer provides, built-into the RAM module. When you install the RAM, the XMP profiles define in which combination of standardized speeds/timings/voltage your memory will run at.
Memory DIMMs incorporate a serial presence detect (SPD) chip which contains information about the memory module. This chip follows a specification defined by JEDEC which includes a number of tables, including reserved entries unused. Intel's XMP standard uses the reserved entries in the SPD for its own purpose: particularly for overclocking purpose.
To examine the XMP profiles of your RAM modules, a good tool isCPU-Z.
Upon boot, the motherboard will examine the XMP profiles of all RAM modules and will choose the best most common profile that it can support (unless the user dictated one in the BIOS for overclocking).
For more information, see the articleExtreme Memory Profile (XMP) - Intelfrom which comes this schema:
