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Newsgroups: | comp.os.msdos.djgpp |
Date: | Tue, 6 Aug 2013 20:56:40 -0700 (PDT) |
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Subject: | Re: Beta Test: CWSDPMI r7 - 4GB support |
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> Let's suppose your computer has 4GB physical memory. Typically between > 2.5GB and 3.5GB of that memory is actually below the 4GB address point. The > remaining typically starts at the 4GB address point. On this computer you > could just sbrk() up to 4092K, > then touch the memory in order (first byte in each 4MB aligned page). I think what you want to express is: the remaining memory will be "re-mapped" to above 4GB address via sbrk(). Am I correct ? > If you then look at the physical map, you will very likely > have at least a 500MB buffer you can configure that actually is above the > 4GB address. Here "at least a 500MB buffer you can configure" means: application(or program) can access this buffer using "indirect" way, am I correct ? (where indirect way means you have to invoke api(or system call) to get pointer first, then access it...) If above is correct, then can I get the "physical memory address" of that buffer ? (the reason I ask is: H/W DMA transfer requires only the physical memory address !) * To sum up, s/w access that buffer(above 4GB physically) indirectly but h/w access it directly(no transform, no remap)
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