PCSX2 Documentation/Virtual Memory: Difference between revisions
PCSX2 Documentation/Virtual Memory (view source)
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#WindowsXP reserves more than half the address space for OS specific stuff. A good amount is also reserved for all of Pcsx2's working memory, executable code, and plugins (especially ZeroGS). It looks like we are left with less than 1.5 Gb of address range to implement the 4Gb PS2 memory map. Note that this problem doesn't exist on 64bit operating systems where the address range is practically... infinite (don't quote me on this 20 years down the road). | |||
#Playstation 2 allows more than one virtual page to point to the same physical page, Windows XP doesn't (I don't know about Linux). Assume that PS2 address 0x1000 points to the same physical page as address 0x0000, each page is 4Kb. Now a write occurs at 0x1000. The game can retrieve that same value just by reading from 0x0000. In Windows XP, this has to be two different pages; so unless some clever solution/technology is discovered, we could kiss our VM dreams goodbye. | |||
The first problem was solved somehow by introducing special address transformations before a read/write occurs. | The first problem was solved somehow by introducing special address transformations before a read/write occurs. | ||
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So the ultimate question is: why doesn't VM work on some computers with 1Gb of RAM and the newest updates, while works on others? Turns out that real-time monitoring applications like to take up some of the 1.5 Gb of left over addresses on certain processes. (this might be OS specific programs too). I have also observed that performance/debugging monitors like NvPerfHud do similar tricks. There probably might be other reasons for VM builds of Pcsx2 not working because virtual memory is a pretty complicated issue. | So the ultimate question is: why doesn't VM work on some computers with 1Gb of RAM and the newest updates, while works on others? Turns out that real-time monitoring applications like to take up some of the 1.5 Gb of left over addresses on certain processes. (this might be OS specific programs too). I have also observed that performance/debugging monitors like NvPerfHud do similar tricks. There probably might be other reasons for VM builds of Pcsx2 not working because virtual memory is a pretty complicated issue. | ||
Moral of the blog Read an OS book. I recommend Operating System Concepts (the dinosaur book) by Abraham Silberschatz, Peter Baer Galvin, Greg Gagne. | '''Moral of the blog''' | ||
Read an OS book. I recommend Operating System Concepts (the dinosaur book) by Abraham Silberschatz, Peter Baer Galvin, Greg Gagne. | |||