Question BIOS doesn't recognize (sometimes) upgraded RAM

[Dimitrisgs]

Hello everyone,

I have a problem with the upgraded RAM. I use a Lenovo laptop with 4GB ram on motherboard. I put an extra RAM (8GB). BIOS sometimes recognize the new RAM, sometimes doesn't. The most of times I see just 4GB ram.

I updated the chipset and BIOS firmware. I put the ram out and installed it again.

Also, I noticed that the soldered RAM has specs:
4GB - SODIMM DDR4 Synchronous 2133MHz
and the extra RAM has specs (from cpu-z software):
8GB - DDR4-2132 1066MHz

However, these are manufacturer's extra RAM's specs:
Kingston
KCP421SD8/8
8GB - SODIMM DDR4 2133MHz

Is there a problem with extra RAM?

Thank you.

Notebook: Lenovo Ideapad 510-15ISK

 

[rgd1101]

exact model of the ram?
cpuz display the clock rate. not transfer rate
and transfer rate is x2 of clock rate

 

[Dimitrisgs]

exact model of the ram?
cpuz display the clock rate. not transfer rate
and transfer rate is x2 of clock rate

This is the model of the RAM:
Kingston KCP421SD8/8