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Branch Prediction in the Pentium Family by Agner Fog

This article describes how the branch prediction mechanism in the Pentium has been uncovered with all its quirks, and the incredibly more effective branch prediction in the later microprocessor versions.

PC Processors Explained By Robert R. Collins

Welcome Computalk readers.

This article was prepared Tom King at Computalk.COM. This brief article provides an overview of the various generations of x86 microprocessors.

Chipsets: The Most important components in a computer system by Billy Newsom

(Following this link will take you away from this web site.)

Have you ever wondered how much difference a chipset makes in the performance of your computer system? This definitive article was submitted by one of my readers. Billy offered, and took it upon himself to write this excellent, and thorough article about computer chipsets, and their relationship to the performance of your computer system.

Sizing Memory In Protected Mode by Robert R. Collins

Have you ever wondered how the BIOS sizes memory? If you have, then you'll want to take a look at this article. In this article, I discuss the basic method which the BIOS uses to determine how many banks of memory, and the size of each DRAM chips.

Protected Mode Virtual Interrupts on the Pentium and SL-Enhanced i486 Intel Processors by Maciej W. Rozycki

This article discloses the last piece of Appendix H information which has not already been disclosed at this web page. Protected Mode Virtual Interrupts (PVI) is supposed to be the protected mode counterpart to VME (Virtual Mode Enhancements, discussed below). However well intentioned Intel was in providing this feature, it's still rather brain-dead and doesn't solve the problem caused by POPF (or IRET) when the EFLAGS image of the interrupt flag needs to be changed. Regardless of the limitations of PVI, this article is invaluable for understanding this secret Pentium feature. The article comes complete with source code and a downloadable executable to demonstrate this feature.

Page Size Extensions on the Pentium Processor by Robert Collins

In order to receive information from Intel regarding the Pentium's 4 MB Page Size Extensions, Intel required you to sign a 15-year NDA. But little did you know that for the past three years, this information has been publicly documented in the Intel i860 XP manual. How ironic!

This article is excerpts from an extensive article I wrote on this subject. Currently, publication rights with a magazine (or two) haven't been ironed out. Therefore, I am unable to publish the entire article. Don't be dismayed, these excerpts will give you enough information and source code to understand all of the pertinent details.

Virtual Mode Extensions on the Pentium Processor by Robert Collins and Jim Brooks

It has taken over four years for this information to be liberated from Appendix H. The people who knew it, couldn't talk about it. Those who didn't know it, wanted it. Now it is finally here: all of the details of the Virtual Mode Extensions on the Pentium Processor. Abundant source code examples are provided as well.

Paging Extensions for the Pentium Pro Processor by Robert Collins

Most people never knew that the Pentium Processor was going to implement 36-bit addressing, and 2-Mbyte pages. As far as I know, these features were implemented in beta silicon, but scrapped for production. Well, they're back on the Pentium Pro Processor, with some other page mode extensions.

Pentium Model-Specific Registers and What They Reveal by Ralf Brown

This is an excellent article by Ralf Brown, the author of the Interrupt List. In this article, Ralf unlocks the secrets to hidden model-specific registers on the Pentium processor and discloses what they contain.

An Overview of Pentium Probe Mode by Robert Collins

This article gives a brief overview of how the Pentium Probe Mode works. What is probe mode used for? How does it work? How does it interface with the Pentium? How do you enter and exit probe mode? All of these topics are discussed in this article.

The Probe Mode Control Register by Robert Collins

The Probe Mode Control Register (PMCR) is also known as the Debug Mode Control Register (DMCR). Many people have seen the DMCR listed in Pentium books, but were never told how to access it. This article not only discloses how to access it, but how to use it to your advantage.

The LOADALL Instruction by Robert Collins

Magazine article by the illustrious Robert Collins (me) in the October 1991 issue of Tech Specialist. In the Annotated Bibliography of Andrew Schulman's book, Undocumented DOS, Second Edition, Andrew says of this article "Collins uses an in-circuit emulator (ICE) to take apart the undocumented LOADALL instruction; an amazingly good article." Thank you Andrew, I think the same of your book.

Protected Mode Basics by Robert Collins

This is an unpublished magazine article I wrote in 1991. I had originally intended to submit it for publication in Tech Specialist, but I eventually lost interest. As I converted the article to hypertext, I was amazed at how informative I had written it (that many years ago). And with my current understanding of the x86 architecture, I detected only one mistake in the article (which I corrected). If you have a desire to know more about protected mode, or learn protected mode basics, then you should read this article. It comes complete with source code, which can be downloaded.

The Story of the CISC King and Appendix H by Robert Collins

This biblical parody chronicals the history of the Intel x86 processors, the creation of Appendix H, and its liberation by a host of shady characters, including, yours truly. The story is not meant to be offensive, though my wife was furious when she read it.