Super User is a question and answer site for computer enthusiasts and power users. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I know in these days this is very stupid question, but for study purposes. I read that when PC starts, CPU is set to read adress just under the 4GB. There should BIOS be mapped to by memory controller.

My question is, in old days, had disabling BIOS shadowing actually freed some RAM for you? I mean, even when BIOS was not shadowed to RAM directly, still adresses for BIOS MMIO access were wasted. And when you cant adress it, its like there is no extra space gained.

share|improve this question

I don't think so.

These areas are overlapping, switching to RAM instead of ROM just gives faster access to this code.

This is done in order to improve computer performance

DOS worked in Real CPU Mode, today's OSes are using Protected mode, so memory management is different

share|improve this answer

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .