Int 2F Fn 4310 - Extended Memory Specification (xms) V2+ - Get Driver Ad [m]
AX = 4310h
Return: ES:BX -> driver entry point (see #2436,#2437,#2440,#2447,#2456,#2461)
Notes: HIMEM.SYS v2.77 chains to previous handler if AH is not 00h or 10h
HIMEM.SYS requires at least 256 bytes free stack space when calling
the driver entry point
See Also: AX=4300h,AX=4310h"Cloaking",AX=4310h"Netroom",AX=4310h"XMZ"
Format of XMS driver entry point:
Offset Size Description (Table 2436)
00h 5 BYTEs jump to actual handler
either short jump (EBh XXh) followed by three NOPs or
far jump (EAh XXXX:XXXX) to a program which has hooked itself
into the XMS driver chain
Note: to hook into the XMS driver chain, a program should follow the chain of
far jumps until it reaches the short jump of the driver at the end
of the chain; this short jump is to be replaced with a far jump to
the new handler's entry point, which should contain a short jump
followed by three NOPs. The new handler must return to the address
pointed at by the short jump which was overwritten. Using this
method, the new handler becomes the first to see every XMS request.
(Table 2437)
Call the XMS driver "Get XMS version number" function with:
AH = 00h
Return: AX = XMS version (in BCD, AH=major, AL=minor)
BX = internal revision number (in BCD for HIMEM.SYS)
DX = High Memory Area (HMA) state
0001h HMA (1M to 1M + 64K) exists
0000h HMA does not exist
See Also: #2438,#2439,#2444,#2445,#2451
(Table 2438)
Call the XMS driver "Request High Memory Area" function with:
AH = 01h
DX = memory in bytes (for TSR or device drivers)
FFFFh if application program
Return: AX = status
0001h success
0000h failure
BL = error code (80h,81h,90h,91h,92h) (see #2462)
Note: HIMEM.SYS will fail function 01h with error code 91h if AL=40h and
DX=KB free extended memory returned by last call of function 08h
See Also: #2439,#2471
(Table 2439)
Call the XMS driver "Release High Memory Area" function with:
AH = 02h
Return: AX = status
0001h success
0000h failure
BL = error code (80h,81h,90h,93h) (see #2462)
See Also: #2438
(Table 2440)
Call the XMS driver "Global enable A20, for using the HMA" function with:
AH = 03h
Return: AX = status
0001h success
0000h failure
BL = error code (80h,81h,82h) (see #2462)
See Also: #2441,#2442,MSR 00001000h
(Table 2441)
Call the XMS driver "Global disable A20" function with:
AH = 04h
Return: AX = status
0001h success
0000h failure
BL = error code (80h,81h,82h,94h) (see #2462)
See Also: #2440,#2443,MSR 00001000h
(Table 2442)
Call the XMS driver "Local enable A20" function with:
AH = 05h
Return: AX = status
0001h success
0000h failure
BL = error code (80h,81h,82h) (see #2462)
Note: this function is used for direct access to extended memory
See Also: #2440,#2443
(Table 2443)
Call the XMS driver "Local disable A20" function with:
AH = 06h
Return: AX = status
0001h success
0000h failure
BL = error code (80h,81h,82h,94h) (see #2462)
See Also: #2441,#2442
(Table 2444)
Call the XMS driver "Query A20 state" function with:
AH = 07h
Return: AX = status
0001h enabled
0000h disabled
BL = error code (00h,80h,81h) (see #2462)
See Also: #2437,#2445
(Table 2445)
Call the XMS driver "Query free extended memory" function with:
AH = 08h
BL = 00h (some implementations leave BL unchanged on success)
Return: AX = size of largest extended memory block in KB
DX = total extended memory in KB
BL = error code (00h,80h,81h,A0h) (see #2462)
Note: this function does not include the HMA in the returned memory sizes
See Also: #2437,#2444,#2446,#2458
(Table 2446)
Call the XMS driver "Allocate extended memory block" function with:
AH = 09h
DX = Kbytes needed
Return: AX = status
0001h success
DX = handle for memory block
0000h failure
BL = error code (80h,81h,A0h) (see #2462)
See Also: #2445,#2448,#2451,#2452,#2453,#2459
(Table 2447)
Call the XMS driver "Free extended memory block" function with:
AH = 0Ah
DX = handle of block to free
Return: AX = status
0001h success
0000h failure
BL = error code (80h,81h,A2h,ABh) (see #2462)
See Also: #2446,#2459
(Table 2448)
Call the XMS driver "Move extended memory block" function with:
AH = 0Bh
DS:SI -> EMM structure (see #2463)
Return: AX = status
0001h success
0000h failure
BL = error code (80h-82h,A3h-A9h) (see #2462)
Note: if either handle in the EMM structure is 0000h, the corresponding
offset is considered to be an absolute segment:offset address in
directly addressable memory
See Also: #2446,#2449
(Table 2449)
Call the XMS driver "Lock extended memory block" function with:
AH = 0Ch
DX = handle of block to lock
Return: AX = status
0001h success
DX:BX = 32-bit physical address of locked block
0000h failure
BL = error code (80h,81h,A2h,ACh,ADh) (see #2462)
Note: MS Windows 3.x rejects this function for handles allocated after
Windows started
See Also: #2446,#2448,#2450
(Table 2450)
Call the XMS driver "Unlock extended memory block" function with:
AH = 0Dh
DX = handle of block to unlock
Return: AX = status
0001h success
0000h failure
BL = error code (80h,81h,A2h,AAh) (see #2462)
See Also: #2449
(Table 2451)
Call the XMS driver "Get handle information" function with:
AH = 0Eh
DX = handle for which to get info
Return: AX = status
0001h success
BH = block's lock count
BL = number of free handles left
DX = block size in KB
0000h failure
BL = error code (80h,81h,A2h) (see #2462)
BUG: MS Windows 3.10 acts as though unallocated handles are in use
Note: MS Windows 3.00 has problems with this call
See Also: #2437,#2446,#2460
(Table 2452)
Call the XMS driver "Reallocate extended memory block" function with:
AH = 0Fh
DX = handle of block
BX = new size of block in KB
Return: AX = status
0001h success
0000h failure
BL = error code (80h,81h,A0h-A2h,ABh) (see #2462)
See Also: #2446,#2455
(Table 2453)
Call the XMS driver "Request upper memory block" function with:
AH = 10h
DX = size of block in paragraphs
Return: AX = status
0001h success
BX = segment address of UMB
DX = actual size of block
0000h failure
BL = error code (80h,B0h,B1h) (see #2462)
DX = largest available block
Notes: Upper Memory consists of non-EMS memory between 640K and 1024K
the XMS driver need not implement functions 10h through 12h to be
considered compliant with the standard
under DOS 5+, if CONFIG.SYS contains the line DOS=UMB, then no upper
memory blocks will be available for allocation because all blocks
have been grabbed by MS-DOS while booting
See Also: #2446,#2454,#2472,INT 21/AH=58h"UMB"
(Table 2454)
Call the XMS driver "Release upper memory block" function with:
AH = 11h
DX = segment address of UMB to release
Return: AX = status
0001h success
0000h failure
BL = error code (80h,B2h) (see #2462)
Note: the XMS driver need not implement functions 10h through 12h to be
considered compliant with the standard
See Also: #2447,#2453,#2455
(Table 2455)
Call the XMS v3.0+ driver "Reallocate upper memory block" function with:
AH = 12h
DX = segment address of UMB to resize
BX = new size of block in paragraphs
Return: AX = status
0001h success
0000h failure
BL = error code (80h,B0h,B2h) (see #2462)
DX = maximum available size (RM386)
Note: the XMS driver need not implement functions 10h through 12h to be
considered compliant with the standard
See Also: #2452,#2453,#2454,#2470
(Table 2456)
Call the QEMM v5.11 "???" function with:
AH = 34h (QEMM 5.11 only, undocumented)
???
Return: ???
See Also: #2457
(Table 2457)
Call the QEMM v5.11 "???" function with:
AH = 44h (QEMM 5.11 only, undocumented)
???
Return: ???
See Also: #2456,#2470
(Table 2458)
Call the XMS v3.0 driver "Query free extended memory" function with:
AH = 88h
Return: EAX = largest block of extended memory, in KB
BL = status (00h,80h,81h,A0h) (see #2462)
ECX = physical address of highest byte of memory
(valid even on error codes 81h and A0h)
EDX = total Kbytes of extended memory (0 if status A0h)
BUG: HIMEM v3.03-3.07 crash on an 80286 machine if any of the 8Xh functions
are called
See Also: #2445,#2459
(Table 2459)
Call the XMS v3.0 driver "Allocate any extended memory" function with:
AH = 89h
EDX = Kbytes needed
Return: AX = status
0001h success
DX = handle for allocated block (free with AH=0Ah) (see #2447)
0000h failure
BL = status (80h,81h,A0h,A1h,A2h) (see #2462)
See Also: #2446,#2458
(Table 2460)
Call the XMS v3.0 driver "Get extended EMB handle information" function with:
AH = 8Eh
DX = handle
Return: AX = status
0001h success
BH = block's lock count
CX = number of free handles left
EDX = block size in KB
0000h failure
BL = status (80h,81h,A2h) (see #2462)
BUG: MS-DOS 6.0 HIMEM.SYS leaves CX unchanged
See Also: #2451,#2459,#2461
(Table 2461)
Call the XMS v3.0 driver "Reallocate any extended memory block" function with:
AH = 8Fh
DX = unlocked memory block handle
EBX = new size in KB
Return: AX = status
0001h success
0000h failure
BL = status (80h,81h,A0h-A2h,ABh) (see #2462)
BUG: HIMEM v3.03-3.07 crash on an 80286 machine if any of the 8Xh functions
are called
See Also: #2452,#2460
(Table 2462)
Values for XMS error code returned in BL:
00h successful
80h function not implemented
81h Vdisk was detected
82h an A20 error occurred
8Eh a general driver error
8Fh unrecoverable driver error
90h HMA does not exist or is not managed by XMS provider
91h HMA is already in use
92h DX is less than the /HMAMIN= parameter
93h HMA is not allocated
94h A20 line still enabled
A0h all extended memory is allocated
A1h all available extended memory handles are allocated
A2h invalid handle
A3h source handle is invalid
A4h source offset is invalid
A5h destination handle is invalid
A6h destination offset is invalid
A7h length is invalid
A8h move has an invalid overlap
A9h parity error occurred
AAh block is not locked
ABh block is locked
ACh block lock count overflowed
ADh lock failed
B0h only a smaller UMB is available
B1h no UMB's are available
B2h UMB segment number is invalid
Format of EMM structure:
Offset Size Description (Table 2463)
00h DWORD number of bytes to move (must be even)
04h WORD source handle
06h DWORD offset into source block
0Ah WORD destination handle
0Ch DWORD offset into destination block
Notes: if source and destination overlap, only forward moves (source base
less than destination base) are guaranteed to work properly
if either handle is zero, the corresponding offset is interpreted
as a real-mode address referring to memory directly addressable
by the processor
Format of XMS handle info [array]:
Offset Size Description (Table 2464)
00h BYTE handle
01h BYTE lock count
02h DWORD handle size
06h DWORD handle physical address (only valid if lock count nonzero)
See Also: #2434