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Topic: Ch-20: Introduction to Protected Virual Address Mode (PVAM) 80286 Microprocessor (Read 592 times) previous topic - next topic

GolamMostafa

Prologue:  IBMPCXTs of the period 1978-1982 were equipped with 8088/8086 processors. These chips had no built-in hardware circuitry to protect the code/data of one user from being accessed/corrupted by the malicious users in a multi-user environment. In 1982, Intel announced the arrival of 80286 which retained 8086 as a core and added 'hardware protection mechanism (HPM)' called 'electronic fence' intended for the protection of code/data. The HPM uses high speed electronic comparators (Fig-20.1) to check the address violation of an asserted instruction and accordingly generates an interrupt without crashing the system. The 80286 has also added 'Memory Management Unit (MMU)' by virtue of which it can execute an application program much larger than the available physical memory. This is known as 'Virtual Address/Memory Support'. The era of IBMPCATs has emerged with PVAM capabilities, which the Intel has still retained in its latest Multi-core architectures. PVAM stands for Protected Virtual Address Mode which essentially refers to the 'Protection Support' and 'Virtual Memory Support' of the 80286. A reader seeks to understand the working principles of the PVAM concepts by performing experiments on an 80286 Microprocessor Trainer for academic purposes and historical perspectives. (XT stands for Extended Technology and AT stands for Advanced Technology.)



Figure-20.1: Protection rule violation check using high speed electronics comparators


westfw


Robin2

I can't even envisage any relevance of an 80386 to this Arduino Forum.

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

GolamMostafa

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Can't you skip right to the 386?
The 80286 was pretty awful.
80286 is the chip in which Intel, for the first time, has implemented their 'Code/Data Protection' mechanism and Virtual Memory scheme. Moreover, the 80286 has retained the full architecture of its predecessor 8086 in line with its own Protectected Mode Register Set. In order to study the PVAM features, we need a Learning System (MicroTalk-80286), which could be (had been realized) built with moderate difficulties based on the Operating System of the 8086 Trainer (MicroTalk-8086). On the other hand, building an 80386 Trainer (MicroTalk-80386) requires (in fact required) tremendous difficulties for booting it up using 16-bit Operating System of the 8086 Trainer through he generation of the dynamic BS16# signal of the 80386. The job of switching over the 80386DX from its Real Mode operation into Protected Mode is still pending!

AWOL

I can't even envisage any relevance of an 80386 to this Arduino Forum.

...R
It's the bar; anything (legal, honest, truthful, decent) goes.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.
I speak for myself, not Arduino.

westfw

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relevance of an 80386 to this Arduino Forum.
  • Correctly categorized in off-topic sub-forum
  • Intel-based arduinos do exist.  (well, DID exist.)
  • most of us are probably using intel cpus to run the IDE.


I've often thought that there should be a course and/or book that covered "comparative microcontrollers."
I'm starting to see how difficult that would be; a lot of the "historically significant" CPUs are no longer very interesting, but the "currently interesting" CPUs lack the sort of diversity you'd like to see, and lose something without the historical perspective...

dannable

Beginners guide to using the Seeedstudio SIM900 GPRS/GSM Shield

GolamMostafa

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Why are you skipping the 80186?
Not much hands-on experience (particularly on the internal peripheral modules of 80186) due to lack of 80186 Trainer during that learning period of 1992.


westfw

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Why are you skipping the 80186?
The  80186 is just an 8086 with some on-chip peripherals (but no memory.)  It's not really "architecturally" interesting.

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