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Lenovo Miix 700: only 2,8GB available out of 4GB RAM

Par Louis Guidez, dans miix700

Hi everybody,

An English post today, because it might help other people around the world. I noticed that under Linux, my PC-tablet Lenovo Miix 700 was only detecting 2,8GB of RAM. Problem: it should have 4GB, and Windows can use them all.

I searched through a lot of forums, and I found out that :

  • Linux was correctly detecting the physical memory (using dmidecode). Not a big surprise though.
  • Linux was only using 256MB for the integrated graphics unit. So where is the missing 1GB ?
  • There was something like a few MB reserved by the BIOS here and there, nothing much, except at the end of the adressable memory. There was a big 1GB hole of "reserved" memory.

1GB is a lot of memory, especially when you only have 4GB installed and it's not upgradable (yeah, soldered to the motherboard, too bad). And it fitted perfectly the missing 1GB... I rebooted my computer to Windows, did some investigation and I was able to see that this 1GB range of addresses was actually seen as "usable" by Windows.

Actually I can't come up with a solution...

What's happening?

I think there's a problem in BIOS firmware. I usually boot Windows directly (i.e. without accessing UEFI boot menu), whereas I use the boot menu to boot Linux (I don't want to use GRUB or another bootloader).

I guess UEFI boot menu uses this 1GB memory, and the this memory isn't released when starting the OS... Which is a bug I tried to submit to Lenovo, without any answer...