Int 2F/AX=4310h

EXTENDED MEMORY SPECIFICATION (XMS) v2+ - GET DRIVER ADDRESS

AX = 4310h

Return:
ES:BX -> driver entry point (see #02749,#02750,#02753,#02760,#02769,#02774)

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

Format of XMS driver entry point: Offset Size Description (Table 02749) 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 02750)
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: #02751 - #02752 - #02757 - #02758 - #02764



(Table 02751)
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 #02775)

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: #02752 - #02784



(Table 02752)
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 #02775)

See Also: #02751



(Table 02753)
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 #02775)

See Also: #02754 - #02755 - MSR 00001000h



(Table 02754)
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 #02775)

See Also: #02753 - #02756 - MSR 00001000h



(Table 02755)
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 #02775)

Note: This function is used for direct access to extended memory

See Also: #02753 - #02756



(Table 02756)
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 #02775)

See Also: #02754 - #02755



(Table 02757)
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 #02775)

See Also: #02750 - #02758



(Table 02758)
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 #02775)

Note: This function does not include the HMA in the returned memory sizes

See Also: #02750 - #02757 - #02759 - #02771



(Table 02759)
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 #02775)

See Also: #02758 - #02761 - #02764 - #02765 - #02766 - #02772



(Table 02760)
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 #02775)

See Also: #02759 - #02772



(Table 02761)
Call the XMS driver "Move extended memory block" function with:.
AH = 0Bh.
DS:SI -> EMM structure (see #02776)

Return:
AX = status
0001h success
0000h failure
BL = error code (80h-82h,A3h-A9h) (see #02775)

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: #02759 - #02762



(Table 02762)
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 #02775)

Note: MS Windows 3.x rejects this function for handles allocated after Windows started

See Also: #02759 - #02761 - #02763 - #02777



(Table 02763)
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 #02775)

See Also: #02762



(Table 02764)
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 #02775)

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: #02750 - #02759 - #02773



(Table 02765)
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 #02775)

See Also: #02759 - #02768



(Table 02766)
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 #02775)
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: #02759 - #02767 - #02785 - INT 21/AH=58h"UMB"



(Table 02767)
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 #02775)

Note: The XMS driver need not implement functions 10h through 12h to be considered compliant with the standard

See Also: #02760 - #02766 - #02768



(Table 02768)
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 #02775)
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: #02765 - #02766 - #02767 - #02783



(Table 02769)
Call the QEMM v5.11 "???" function with:.
AH = 34h  (QEMM 5.11 only, undocumented).
???

Return:
???

See Also: #02770



(Table 02770)
Call the QEMM v5.11 "???" function with:.
AH = 44h  (QEMM 5.11 only, undocumented).
???

Return:
???

See Also: #02769 - #02783



(Table 02771)
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 #02775)
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: #02758 - #02772



(Table 02772)
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 #02760)
0000h failure
BL = status (80h,81h,A0h,A1h,A2h) (see #02775)

See Also: #02759 - #02771



(Table 02773)
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 #02775)

BUG: MS-DOS 6.0 HIMEM.SYS leaves CX unchanged

See Also: #02764 - #02772 - #02774



(Table 02774)
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 #02775)

BUG: HIMEM v3.03-3.07 crash on an 80286 machine if any of the 8Xh functions are called

See Also: #02765 - #02773

(Table 02775) 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 02776) 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 02777)
00h    BYTE    handle
01h    BYTE    lock count
02h    DWORD   handle size
06h    DWORD   handle physical address (only valid if lock count nonzero)

See Also: #02747 - #02762

Category: Memory Management - Int 2Fh - E

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