Subject: Re: pmap
To: None <>
From: Michael L. Hitch <>
List: amiga-dev
Date: 03/20/1994 19:10:51
On Mar 20,  9:33am, newsham@uhunix.uhcc.Hawaii.Edu wrote:
> I'm a bit confused about one detail in the pmap and vm system.  There
> are two page sizes defined,  PAGE_SIZE = 4096 and AMIGA_PAGE_SIZE = 8192.
> When the kernel steals pages for its own use it seems to be grabbing
> AMIGA_PAGE_SIZE sized chunks.  atop() which should convert an address
> into pages does a >> page_size, page_size is initialized to 12 by the
> vm system (2^12 = 4096). 
> One of the things I have to do to use MACHINE_NONCONTIG is to make routines
> reporting how many pages left and another routine to pass the address
> of the next page.   Should I be using PAGE_SIZE and atop() or should
> I be handing out AMIGA_PAGE_SIZE pages and using >> 13 to get the number
> of pages?
> What is the purpose of the two different page sizes?

  PAGE_SIZE is 8192 on the Amiga.

  If you look deep enough, you will find:
  - PAGE_SIZE is defined to be page_size.
  - page_size is initialized to 4096.
  - start_c sets page_size to 8192.


Michael L. Hitch			INTERNET:
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Montana State University	Bozeman, MT	USA