Tutorial by Examples

History The first computers Early computers had a block of memory that the programmer put code and data into, and the CPU executed within this environment. Given that the computers then were very expensive, it was unfortunate that it would do one job, stop and wait for the next job to be loaded in...

High Level Design The 80386 is a 32-bit processor, with a 32-bit addressable memory space. The designers of the Paging subsystem noted that a 4K page design mapped into those 32 bits in quite a neat way - 10 bits, 10 bits and 12 bits: +-----------+------------+------------+ | Dir index | Page ind...

The 80486 Paging Subsystem was very similar to the 80386 one. It was backward compatible, and the only new features were to allow for memory cache control on a Page-by-Page basis - the OS designers could mark specific pages as not to be cached, or to use different write-through or write-back caching...

When the Pentium was being developed, memory sizes, and the programs that ran in them, were getting larger. The OS had to do more and more work to maintain the Paging Subsystem just in the sheer number of Page Indexes that needed to be updated when large programs or data sets were being used. So th...

Introduction As memory prices dropped, Intel-based PCs were able to have more and more RAM affordably, alleviating many users' problems with running many of the ever-larger applications that were being produced simultaneously. While virtual memory allowed memory to be virtually "created" ...

Since the Physical Address Extension (PAE) mode that was introduced in the Pentium Pro (and Pentum M) was such a change to the Operating System memory management subsystem, when Intel designed the Pentium II they decided to enhance the "normal" Page mode to support the new Physical Address...