Query: How to get RAM size of system about grub

[a1ive]

Legacy-BIOS? I have no idea.

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On Fri, Apr 17, 2020, 14:38 Steve Si ***@***.***> wrote: In grub4dos I can get the total amount of RAM in a system. How can I do this with grub2 (MBR and UEFI)? For instance, I can automatically select a 32-bit install of Windows from a dual architecture ISO if the system has <4GB of RAM. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#55>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ACRNAGUXZA4OQIXQFJEVQMLRM72OPANCNFSM4MKPWAAQ> .

[steve6375]

UEFI BIOS?

[a1ive]

I can automatically select a 32-bit install of Windows from a dual architecture ISO if the system has <4GB of RAM.

You can't boot/install a 32-bit Windows if UEFI firmware is 64-bit.

[steve6375]

Sure , in that case I was thinking of Legacy boot.
But you can run Linux 32-bit kernels from UEFI64 boot (for instance).

[a1ive]

But you can run Linux 32-bit kernels from UEFI64 boot (for instance).

compatibility of 32-bit linux is bad. It doesn't work no some tablets with 64-bit CPU/UEFI.
besides many linux distros (eg. Ubuntu) have dropped support for 32-bit.

[a1ive]

Sure , in that case I was thinking of Legacy boot.

How to get the total amount of RAM in grub4dos?

[steve6375]

set /a M=*0x8298 & 0xffffffff>>10+1 > nul && set /a M1=*0x82c0>>10+1 > nul
set /a M=%M% + %M1% > nul

grub4dos has documented memory location where it is stored.
0000:8298 4 (DWORD) saved_mem_upper (extended memory size in KB)
0000:82C0 8 (QWORD) saved_mem_higher (max contiguous mem in KB starting at 4G

can do a BIOS call, int15 e820h
https://wiki.osdev.org/Detecting_Memory_(x86)#BIOS_Function:_INT_0x15.2C_EAX_.3D_0xE820

See grub4dos stage2\common.c for code.

[steve6375]

That is showing memory above 4GB
You need to add up all conv-mem entries to get total memory?

[steve6375]

What variable is the result returned in?
--set=VAR work ?

[a1ive]

download latest build.
stat -q -r -s a
echo $a

[steve6375]

Thanks. MBR result agrees with grub4dos within +/-1. 👍

[steve6375]

Thanks - great work!