To PSE or not to PSE, that's the question

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TopSekret
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To PSE or not to PSE, that's the question

Post by TopSekret »

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**
madanra
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Re: To PSE or not to PSE, that's the question

Post by madanra »

Personally, I'd stick to 64-bit, where the decision is made for you.
Octocontrabass
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Re: To PSE or not to PSE, that's the question

Post by Octocontrabass »

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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Ch4ozz
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Re: To PSE or not to PSE, that's the question

Post by Ch4ozz »

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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