Computer Systems

It'll have a been a while since I picked up my study on architecture and systems.

In the last post discussing computer systems, I mentioned the following:

Will therefore:

• first learn more about the operations, registers, etc... for the x86_64 architecture (though I might change to a simpler architecture)
• then come back to the linking step, and feel a lot more comfortable reading the contents of object files, and everything else

I have therefore started reading more on the x64 architecture.

I had a hard time understanding the flat and segmented memory models, and so as I always do, started reading about x64's predecessors.

This gave me a high level overview of the architecture's genealogy, starting at the Intel 8080 (16 bit), then Intel 8086 (16 bit + segmented memory model), to the Intel 80386 / i386 (32 bit), and finally the x64 based chips

From there, I decided it was a good idea to start understanding learn about computer architecture concepts through the Intel 8086 rather than x64 chips / architecture in order to reduce complexity and gain a historical understanding.

The Intel 8086 was a really good sandbox for me to learn the concepts I had a hard time grapling with, namely I got a pretty solid feeling for:

• Segmented vs flat memory model
• The address and data buses
• Address decoders
• The basic layout of circuitry that connected peripherals to the CPU
  • this includes the CPU placing a particular value on its buses
  • the fact that on the 8086, the buses are shared for part of the circuitry
  • each address decoder then activate (Chip Select) or not their corresponding device (memory mapped IO and isolated IO)
  • when activated, each device has then a second line to read the required data from the buses

The next things I have to understand are:

• How is memory (or/and other peripherals) responding to the activation by the decoder.
• Eventually, how did the CPU get its instruction in the first place

Leetcode

Revisited problems

198. House Robber

189. Rotate Array

2058. Find the Minimum and Maximum Number of Nodes Between Critical Points