From:	blade DOT runner DOT shoots AT another DOT spam DOT bot (Alfons Hoogervorst)
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Porting Symantec code to DJGPP
Date:	Wed, 30 Jul 1997 17:08:01 GMT
Organization:	The Programming with Puns Facility
Message-ID:	<33df729f.14585936@news3.worldaccess.nl>
References:	<33DC7784 DOT 2781 AT informatik DOT uni-bonn DOT de>
NNTP-Posting-Host:	193.67.132.221
Lines:	63
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Lo Alexander von Luenen <luenen AT informatik DOT uni-bonn DOT de>:

From the Symantec RTL docs:

-----------------------8<----------------------

_x386_map_physical_address
--------------------------

Prototype

void *_x386_map_physical_address(void *abs_addr,
  unsigned size);

Description

This function maps specific physical addresses. The abs_addr argument
specifies the start address of the physical memory to map. The size
argument indicates the size of the region, in bytes. The function is
implemented for the X memory model only.

Typically, you use this function to access memory mapped I/O devices.
The region to be mapped must be completely above or completely below
the 1MB boundary; it cannot lap over the boundary itself. The function
will fail and return -1 if memory is insufficient or if the DPMI host
refuses service. X-32 must allocate a minimum of 4 KB for each
_x386_map_physical_address call.

Return Value

A near pointer that can be used to access the actual physical address
requested. The device will not be accessible at the actual physical
address; it will appear to be at the address returned by this
function.

Compatibility

Phar Lap, DOSX 

----------------------->8----------------------

Search the DJGPP docs for __dpmi_physical_address_mapping().

>   ushort AMem::MallocLow(ushort size)
>   {
>      union REGS regs;
>      regs.h.ah=0x48;
>      regs.x.bx=(size+15)>>4;
>      int86_real(0x21, &regs, &regs);
>      return (regs.x.ax);
>   }

int86_real() sends an interrupt to DOS, it doesn't go through the
interrupt handlers of the DOS extender. DJGPP: 

__dpmi_simulate_real_mode_interrupt()

Bye.

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