Meminfo.c32
Meminfo.c32 displays the range/size of various memory functions.
Contents
Example
Here's an example (with some extra formatting for clarity) from within bochs with 64 MiB of RAM.
| boot: meminfo.c32 | |||||
| INT 15h = f000:f859 DOS RAM: 639K (0x9fc00) INT 12h: 639K (0x9fc00) | |||||
| INT 15 88: 0xfc00 (64512K) INT 15 E801: 0x3c00 (15360K) 0x0300 (49152K) | |||||
| 0 1 2 3 4 5 |
0000000000000000 000000000009f000 00000000000e8000 0000000000100000 0000000003ff0000 00000000fffc0000 |
000000000009f000 0000000000001000 0000000000018000 0000000003ef0000 0000000000010000 0000000000040000 |
000000000009f000 00000000000a0000 0000000000100000 0000000003ff0000 0000000004000000 0000000100000000 |
1 [-] 2 [-] 2 [-] 1 [-] 3 [-] 2 [-] |
usable reserved reserved usable ACPI reclaim reserved |
Meaning
INT 15h e820
Results from INT 15h AX=e820h.
This is, for the most part, the most important of all of the memory functions,
as it provides a map of available memory.
The information is displayed as the last few lines of the output
(in this instance, 6) starting (in the example) with:
| 0 | 0000000000000000 | 000000000009f000 | 000000000009f000 | 1 [-] | usable |
Line numbers are printed in hex as 8 characters wide with a space prefix. Each line represents the purpose/availability, address and length/size of a block of memory.
The first 64 bit hex quantity is the start address. The second is the length/size. The third is the end address (excluding the listed byte; calculated as start plus length). The next number is decimal for the type of memory. The next column is bracketed, either a single hyphen or a hex number representing the extended attributes.
The last column is the string representation of the type:
- 1: usable
- 2: reserved
- 3: ACPI reclaim
- 4: ACPI NVS
- 5: unusable
INT 15h
INT 15h = f000:f859 DOS RAM: 639K (0x9fc00) INT 12h: 639K (0x9fc00) |
List the segment and offset of the INT 15h handler,
as read from the interrupt vector table.
DOS RAM
INT 15h = f000:f859 DOS RAM: 639K (0x9fc00) INT 12h: 639K (0x9fc00) |
It appears that this reads a value directly from memory.
INT 12h
INT 15h = f000:f859 DOS RAM: 639K (0x9fc00) INT 12h: 639K (0x9fc00) |
The results from calling INT 12h.
List the available low memory (under 640k).
INT 15h 88
INT 15 88: 0xfc00 (64512K) INT 15 E801: 0x3c00 (15360K) 0x0300 (49152K) |
Results from INT 15h, AH=88h.
Return the size of extended memory (total RAM in KiB as a 16 bit quantity).
INT 15h e801
INT 15 88: 0xfc00 (64512K) INT 15 E801: 0x3c00 (15360K) 0x0300 (49152K) |
Results from INT 15h AX=e801h.
Extended memory size with a larger limit (superseding AH=88h).
The first pair of values is the return (in CX) and size of memory between 1 MiB and 16 MiB.
The second pair of values is the return (in DX) and size of memory above 16 MiB in 64 KiB pages.
