Support for 4 chips, 8bit ddr3 either 512m*8 or 1G*8?

[PickledFins]

Hey All,

So I know it's mentioned in the data sheet that the stm32mp1xx MPU's only support 16/32 bit DDR ram, and that it also mentions the limit of 1GByte total ram,  but I just wanted to confirm this isn't possible and specifically why as I cannot find out much about what is the limiting factor here.

For example this IC:

https://au.mouser.com/ProductDetail/Intelligent-Memory/IM8G08D3FFDG-125I?qs=Y0Uzf4wQF3k9cXZekshqqQ%3D%3D

Alternatively, could I push it up to 2GBytes by adding an additional MPU with its on 1GB of ram whilst also pushing it up as a quad core system?

And if so, what the best communication method would be between them.

Thanks in advance for any help!

[PatrickF · Accepted solution]

Hi @PickledFins 

Although support of 4 x DDR3L x8 chips might be possible, this will not allows to go beyond 1GBytes of memory.

4 x DDR3L devices on the PCB might make signal routing more complex and hard to cope with guidelines of AN5122

Note that the memory you mention is using 2 x CS (so dual rank) which is not supported for STM32MP1 controlled.

Maybe question if you really need more than 1GBytes of RAM in your system.

Using 2 x STM32MP1 on same board is possible, but then your system should be particularly well split to benefit of this as making interface between both will be quite complex (I guess easy connection it to use external Ethernet switch). Using 'slow' interfaces like SPI or UART is also possible, but largely depend on your use case.

Regards.