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 Post subject: To PSE or not to PSE, that's the question
PostPosted: Thu Apr 20, 2017 8:11 am 
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Joined: Thu Apr 20, 2017 7:45 am
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As you probably all know, adding support for more paging schemas (486, PSE, PSE-36, PAE, 4L) is hours of work.

My question is: is having PSE support (after having PSE, PSE-36 is very simple) worth a few hours?

Pros:
  • Support for 4MB pages (PAE has only 2MB)
  • The same structures as 486 paging
  • Strips one layer of Page Lookup = faster

Cons:
  • No NX bit
  • PSE-36 is a piece of sh**

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 Post subject: Re: To PSE or not to PSE, that's the question
PostPosted: Thu Apr 20, 2017 9:14 am 
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Personally, I'd stick to 64-bit, where the decision is made for you.


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 Post subject: Re: To PSE or not to PSE, that's the question
PostPosted: Thu Apr 20, 2017 1:41 pm 
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Pros:
  • PSE might be faster than PAE (thanks to larger pages and smaller page tables)
  • Some (very old?) CPUs support PSE but not PAE

Cons:
  • PSE might be slower than PAE (it's probably not an optimization target for Intel or AMD)
  • Accessing memory above 4GB requires PSE-36
  • PSE-36 might be slower than PAE (since you can't use 4kB pages above 4GB)
  • Some (very old?) CPUs support PAE but not PSE-36
  • NX/XD requires PAE

If you're specifically targeting non-PAE hardware, it might be worthwhile to support PSE (but not PSE-36); otherwise, stick to PAE or switch to 64-bit.


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 Post subject: Re: To PSE or not to PSE, that's the question
PostPosted: Thu Apr 20, 2017 3:42 pm 
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Hm, I'd consider using PAE for the NX bit only, if your looking for more RAM covering you should simply move to long mode
PSE sounds like a feature nobody would even expect from an OS since PAE and 64 bit were designed


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