درصورتی که مطالب داخل منبع اصلی برای شما در دسترس نیست، ادامه همین پست را بروید.
Go inside the computer to uncover the inner workings of the CPU including the Control Unit, the ALU, registers and much more.
See the Book: https://amzn.to/1mOYJvA Author's Website: https://www.buthowdoitknow.com/
See the 6502 CPU Simulation: https://visual6502.org/JSSim/index.html
For anyone annoyed by the breaths between speaking, try this unlisted version with edited audio: https://www.youtube.com/watch?v=IkdBs...
Download the PowerPoint file used to make the video: https://docs.google.com/file/d/0BzwHN...
The CPU design used in the video is copyrighted by John Scott, author of the book But How Do It Know?.
There
are a few small differences between the CPU in the video and the one
used in the book. Those differences are listed below but they should not
detract from your understanding of either.
CONTROL UNIT - This
component is called the Control Section in the book. It is called
Control Unit here simply because that is a more common name for it that
you might see used elsewhere.
LOAD INSTRUCTION - In this video,
what's called a LOAD instruction is actually called a DATA instruction
in the book. The Scott CPU uses two different instructions to move data
from RAM into the CPU. One loads the very next piece of data (called a
DATA instruction in the book) and the other uses another register to
tell it which address to pull that data from (called a LOAD instruction
in the book). The instruction was renamed in the video for two reasons:
1) It might be confusing to hear that the first type of data we
encounter in RAM is itself also called DATA. 2) Since the LOAD
instruction from the book is a more complex concept, it was easier to
use the DATA instruction in the video to introduce the concept of moving
data from RAM to the CPU .
IN and OUT INSTRUCTIONS - In the
Scott CPU, there is more involved in moving data between the CPU and
external devices than just an IN or an OUT instruction. That process was
simplified in the video to make the introduction of the concept easier.
ACCUMULATOR - The register that holds the output of the ALU is
called the Accumulator in the book. That is the name typically used for
this register, although it was simply called a register in the video.
MEMORY
ADDRESS REGISTER - The Memory Address Register is a part of RAM in the
book, but it is a part of the CPU in the video. It was placed in the CPU
in the video as this is generally where this register resides in real
CPUs.
JUMP INSTRUCTIONS - In the book there are two types of
unconditional JUMP instructions. One jumps to the address stored at the
next address in RAM (this is the one used in the video) and the other
jumps to an address that has already been stored in a register. These
are called JMP and JMPR instructions in the book respectively.
MISSING
COMPONENT - There is an additional component missing from the CPU in
the video that is used to add 1 to the number stored in a register. This
component is called "bus 1" in the book and it simply overrides the
temporary register and sends the number 1 to the ALU as input B instead.
REVERSED
COMPONENTS - The Instruction Register and the Instruction Address
Register are in opposite positions in the diagrams used in the book.
They are reversed in the video because the internal wiring of the
control unit will be introduced in a subsequent video and keeping these
registers in their original positions made that design process more
difficult.
OP CODE WIRING - The wires used by the control unit
to tell the ALU what type of operation to perform appear near the bottom
of the ALU in the video, but near the top of the ALU in the book. They
were reversed for a similar reason as the one listed above. The wiring
of the ALU will be introduced in a subsequent video and keeping these
wires at the top of the ALU made the design process more difficult.