On Jan 10, 1:11 am, xmllmx <spamt...@[EMAIL PROTECTED]
> wrote:
> I'm curious to know how to check the RAM size installed on the machine
> in x86 assembly language.
>
> In addition, there is a related question in my mind: Must the physical
> addresses of the RAM be contiguous? For example, provided that I have
> two RAM chips and the size of each is 16M, my PC's mainboard has 3
> slots to install RAM chips, let me number them as slot 0, slot 1, and
> slot 2. Assuming the addressing hardware numbers the address space
> from slot0 through slot2 (i.e. physical address 0 will be allocated to
> slot0 if it is equipped with a RAM chip). If I plug the two RAM chips
> into slot0 and slot2, and let slot1 empty. In this case, is the first
> 32M of the physical address space contiguous?
>
> I guess (am not very sure) the addressing hardware will guarantee the
> physical address space to be contiguous. For example, if the total RAM
> size is 32M, then the physical addresses from 0 to 32M are always
> addressable, no matter which slots the RAM chips occupy. Am I correct?
>
> Any help will be highly appreciated. Thanks in advance!
Regardless, if contiguous, the system may not map it as contiguous.
Here is some of Frank's code and sample output of int15h ax.E820h...
"
;;I've been meaning to investigate this interrupt ever since I first
heard
;of it. Your question prompted me to whip up this crude example. I
don't
;really know if it's "right" or not... seems reasonable... Here's the
;output from the sucker on my machine:
[MAP NE820.MAP]
;0000000000000000
;000000000009FC00
;00000001 1=Avail. to OS, 2=Not Avail.,
;000000000009FC00
;0000000000000400 2=Not Avail, Extended Bios Data Area here.
;00000002
;00000000000F0000
;0000000000010000
;00000002
;00000000FFFF0000
;0000000000010000
;00000002
;0000000000100000
;0000000007F00000
;00000001
;I'm not sure what's in those "reserved" blocks... better not mess
with
;them... (or *do*, and see what happens :)
;I don't know if this is any help to you... something to play with,
anyway.
;Best,
;Frank
; nasm -f bin -l ne2.lst -o ne2.bin ne2.asm
;org 100h
section .text
struc mm_ent
.base resq 1
.len resq 1
.type resd 1
endstruc
section .text
mov di, buffer
xor ebx, ebx
xor si, si ; counter
top:
mov eax, 0E820h
mov edx, 534D4150h ; 'SMAP'
mov ecx, 20
int 15h
jc error
inc si ; bump counter
add di, cx
or ebx, ebx
jz done
jmp short top
done:
mov cx, si ; count
mov si, buffer
show:
mov eax, [si + mm_ent.base + 4]
call showeax
mov eax, [si + mm_ent.base]
call showeax
call newline
mov eax, [si + mm_ent.len + 4]
call showeax
mov eax, [si + mm_ent.len]
call showeax
call newline
mov eax, [si + mm_ent.type]
call showeax
call newline
add si, mm_ent_size
; cmp si, di ; this worked too, but I thought it
; jne show ; might be "safer" to count blocks
loop show
error:
exit:
ret
;------------------
showeax:
push cx
mov cx, 8
..top:
rol eax, 4
push eax
and al, 0Fh
cmp al, 0Ah
sbb al, 69h
das
call putc
pop eax
loop .top
pop cx
ret
;-------------------
;-------------------
newline:
push ax
mov al, 13
call putc
mov al, 10
call putc
pop ax
ret
;--------------------
;--------------------
putc:
push ax
push dx
mov dl, al
mov ah, 2
int 21h
pop dx
pop ax
ret
;----------------
;;section .bss
buffer TIMES 200h db 0
;---------------------
"
...also..
mtypes db ' Types: 1=Avail. to OS, 2=Not Avail., '
db '3=ACPI Avail. to OS, 4=NVS Not Avail. '
hth,
Steve
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