Jack wrote:
> Japheth,
> I noted your reply to Eric Auer on FD-User re: the idea of
> over 4-GB for DOS, in which you wrote:
>> PAE paging most likely isn't needed, the simpler approach
>> "32-bit paging with 4 MB pages" should do as well.
> What is this??  I have seen the Intel specs for PAE memory
> but I did not see this.  Is it an "option" that I missed??

The paging modes are described in

http://www.intel.com/Assets/PDF/manual/253668.pdf     , chapter 4.

In short: 32bit-paging with 4 MB paging allows full access to 64 GB and 
support for this feature is relatively simple to implement in Jemm.

> So I wanted to ask:  What do you think about over 4-GB for
> DOS??    Is it needed, might be needed at a later time, or
> may NEVER be needed??

IMO a DOS environment should support at least the full 4 GB, anything more is 
"nice to have". However, many PCs with 4 GB or more are configured in a way 
that only 2 GB are below the 4 GB border. The rest is "inaccessible" then for 
DOS memory managers. This can - and IMO should - be improved. This task is 
pretty simple for Jemm, because it uses paging already. For the Himems, the 
implementation will be "slightly advanced", since they have to temporarily 
enable paging to access the memory.

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