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Performance

 
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testcrap
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Joined: 25 Mar 2010
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PostPosted: Thu Mar 25, 2010 10:42 am    Post subject: Performance Reply with quote

Is there a performance hit in using dbvm when running games? It would be nice to have some more documentation on how this whole thing works exactly. And i also want to thank u guys generally for the whole project, im such a noob and without cheatengine i would have no fun playing games.
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Dark Byte
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Joined: 09 May 2003
Posts: 25262
Location: The netherlands

PostPosted: Thu Mar 25, 2010 2:03 pm    Post subject: Reply with quote

there is a very slight performance hit, especially noticeable when running 16-bit applications outside of windows

Besides that the default configuration (non debug version) shouldn't give a noticable speed difference (except when you start benchmarking explicitly on some stuff that the vm has to handle you might see some slowdowns)

Also, what do you want to know specifically about dbvm ?
Some questions:
Q: Can you use kernelmode debugging in 64-bit with dbvm?
A: Yes

Q: Will just running dbvm make me able to find values I usually could not?
A: No

Q: Will running dbvm prevent me from getting banned when I cheat?
A: No

Q: Can I use the secret stealthedit plugin that was posted on another forum with dbvm so I can edit code without the game seeing it ?
A: Yes

Q: I have an amd, can I use dbvm?
A: No

Q: Is dbvm undetected?
A: Not in the version shipped with ce 5.6. (It changes your cpuid to "Intel Fuck")

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testcrap
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Joined: 25 Mar 2010
Posts: 27

PostPosted: Thu Mar 25, 2010 2:26 pm    Post subject: Reply with quote

i just wante to use this to cheat offline, i had problems with game crashing as soon as the debugger was attached. and i was wondering about the speed cause i once tested another vm and there was a very noticeable performance hit. and i just wanted to know more about dbvm cause i find it interesting. i wonder how does it work, like does it check every single instruction before the cpu executes the instruction. so i was asking for an explanation with some pictures and pseudo-code on how this vm works.
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Dark Byte
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Location: The netherlands

PostPosted: Thu Mar 25, 2010 2:43 pm    Post subject: Reply with quote

if you're on 32-bit, try the kernelmode debugger without dbvm
if you're on 64-bit, then you'll have to use dbvm yes

as for the speed, compared to those dbvm is lightning fast as it doesn't emulate the graphics card, it has raw access to the hardware (most of it)

which brings us to the basics of how dbvm works:
flow of code:
Code:

dbvm: Configure cpu
dbvm: Launch cpu
virtual cpu:run code until break
<break> <----------------------------
dbvm:handle break                   ^
dbvm:continue virtual cpu       --->|




At one point the system will launch dbvm (at boot or when ce offloads to dbvm), and setup virtual cpu's based on the number of actual cpu's
Then it configures those virtual cpu's to the exact same state as the real cpu states and tells each cpu to run in the virtual cpu mode

Then there are some events that can cause the virtual cpu to switch back to normal mode and let the dbvm software emulate the event (e.g cpuid, or access to specific cpu data that might be modified by dbvm)

dbvm does not execute every single cpu instruction, unless it is running in 16-bit realmode, but since no windows version since windows 95 doesn't run 16-bit realmode (the 32-bit ones do support 16-bit protected mode) that's no problem

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testcrap
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Joined: 25 Mar 2010
Posts: 27

PostPosted: Thu Mar 25, 2010 3:56 pm    Post subject: Reply with quote

ah thx, that maked things pretty clear. keep up the good work!
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