Using a high frequency LPDDR3 RAM with a lower RAM frequency supported Processor

Question

I'm designing a board with Allwinner A64 processor and i'm confused in choosing the proper RAM. the SDRAM controller characteristics of the processor is listed as follows:

• Compatible with JEDEC standard DDR2 /DDR3 /DDR3L/LPDDR2/LPDDR3 SDRAM
• Support clock frequency up to 667MHz(DDR3-1333)
• Support 2 chip selects
• Up to 3GB address space
• 32-bits bus width
• 16 address signal lines and 3 bank signal lines
• Support Memory Dynamic Frequency Scale(MDFS)

I need to choose a 1GB LPDDR3 SDRAM. the question is that is it possible to use a DDR3-1866 RAM(for example Samsung_K4E8E324EB-AGCF)? In fact I don't expect the processor to interact with the ram with 1866 data-rate. i just want to know if the processor works with a higher data-rate ram but it just use the processor's last data-rate ability(DDR3-1333 in this case).

if it's not possible, any other suggestion would be appreciated. in banana pi BPI-M64 4 separate 512MB Micron RAMs with 8-bit BUS are used to create a 2GB RAM. but the model of Ram is not specified and i can't find it anywhere.

Thanks.

Answer 1

In general, if you have a particular speed memory interface, then any memory device that can operate at that speed or faster should work just fine.

This is certainly true in the DDR world (mainly due to it being made to a standard) - I have had to support long term products and the fact is memory devices become obsolete very quickly (simply because the vendors are not interested in making slow devices as the market is not there). The slow devices fall off the product listing.

I simply put in devices capable of higher speeds with no issues at all.

I would check the timing parameters, though (for both memory and processor); the datasheet information is the true arbiter of what will work together.