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DOS开发编程 & 发展交流（开发室） » You can directly access 4GB of memory like this in real mode

Floor1　lxdddxl	Posted 2003-12-23 00:00
初级用户　Posts 6　Credits 122
Make sure config.sys contains device=c:\dos\himem.sys dos=high There absolutely must not be emm386.exe. This ensures the CPU is in real mode rather than V86 mode, and that A20 is also enabled. Then you can do whatever you want in the program, for example xor ax,ax mov ds,ax mov eax,12345678h mov bx, mov esi,40000000h dec dword ptr Unfortunately, none of the high-level language development tools under DOS support this kind of data access method, so you can only use assembly.

Floor2　Wengier	Posted 2003-12-23 00:00
系统支持　Posts 10,521　Credits 27,736
Would it be possible to write a patch program for real-mode C compilers like TC and BC?

Floor3　dwing	Posted 2004-01-14 00:00
初级用户　Posts 32　Credits 177
In real mode you can use the XMS interface to access it but I still recommend using Watcom or djgpp.

Floor4　allan^	Posted 2004-03-23 00:00
初级用户　Posts 5　Credits 110
Question for DWING in post #3: what method can WATCOM use to do this? The function is very simple, I just need to access data in memory beyond the 1MB range. I currently have no idea where to start.

Floor5　allan^	Posted 2004-03-24 00:00
初级用户　Posts 5　Credits 110
I already figured out how to access it, and now I'm starting to appreciate how powerful WATCOM is.