[off] memory management in the PC

[Ricardo Bittencourt Vidigal Leitao]

On Thu, 26 Aug 1999, Giovanni R. Nunes wrote:

>   And don't forget! What means "pia" in portuguese? :)

        That's easy, "pia" means "boy" or "child".

        Someone asked about PC memory management in real mode. There are
three ways to do it:

        1) XMS: with this method you can access the pc bios to copy blocks
from high memory to low memory (and the other way too). This is slow since
it requires the use of "rep movsd" or equivalent.

        2) EMS: in this one you can map the high memory in the low memory,
the same way we do in the Memory Mapper or the MegaRAM. This is slow since
it puts the processor in virtual86 mode, and the "in" and "out" opcodes
can get as much as twelve times slower.

        3) UMB: this option lets you manage the hole between 640kb and
1Mb, but it should not be used to let this space free for LOADHIGH
device drivers.

        In short, memory management in the PC sucks.

----------------------------------------------------------------
Ricardo Bittencourt               http://www.lsi.usp.br/~ricardo
[EMAIL PROTECTED]  "Ricardo is subtle, but malicious he is not"
------ Uniao contra o forward - crie suas proprias piadas ------


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