Note: This API calls are shared between DOS and Win16 personality.
DPMI is a shared interface for DOS applications to access Intel 80286+ CPUs services. DOS DMPI host provides core services for protected mode applications. Multitasking OS with DOS support also provides DMPI in most cases. Windows standard and extended mode kernel is a DPMI client app. Standard and extended mode kernel differs minimally and shares common codebase. Standard Windows kernel works under DOSX extender. DOSX is a specialized version of 16-bit DPMI Extender (but it is standard DPMI host). Standard mode is just DPMI client, exnhanced mode is DPMI client running under Virtual Machime Manager (really, multitasker which allow to run many DOS sessions). Both modes shares DPMI interface for kernel communication. The OS/2 virtual DOS Protected Mode Interface (VDPMI) device driver provides Version 0.9 DPMI support for virtual DOS machines. Win16 (up to Windows ME) provides Version 0.9 DPMI support.
DPMI host often merged with DPMI extender. Usually DPMI extender provide DPMI host standard services and DOS translation or True DPMI services.
Int 31H, AH=05H, AL=0BH
Get Memory Information
AX = 050BH ES:(E)DI = selector:offset of 128-byte buffer
if function successful Carry flag = clear (this function always succeeds in DPMI 1.0) and the buffer pointed to by ES:(E)DI is filled in with the following information:
|00H||4||Total allocated bytes of physical memory controlled by DPMI host|
|04H||4||Total allocated bytes of virtual memory controlled by DPMI host|
|08H||4||Total available bytes of virtual memory controlled by DPMI host|
|0CH||4||Total allocated bytes of virtual memory for this virtual machine|
|10H||4||Total available bytes of virtual memory for this virtual machine|
|14H||4||Total allocated bytes of virtual memory for this client|
|18H||4||Total available bytes of virtual memory for this client|
|1CH||4||Total locked bytes of memory for this client|
|20H||4||Maximum locked bytes of memory for this client|
|24H||4||Highest linear address available to this client|
|28H||4||Size in bytes of largest available free memory block|
|2CH||4||Size of minimum allocation unit in bytes|
|30H||4||Size of the allocation alignment unit in bytes|
|34H||4CH||Reserved, currently zero|
if function unsuccessful Carry flag = set (this function always fails in DPMI 0.9)
Returns information about available physical and virtual memory. Since DPMI clients will often run in multitasking environments, some of information related to shared resources returned by this function should only be considered as advisory.
DPMI 1.0 clients should use this function in preference to Int 31H Function 0500H.
The “total available bytes” field of the data structure pointed by ES:(E)DI means the total bytes minus all of the allocated bytes.
Text based on http://www.delorie.com/djgpp/doc/dpmi/