PowerPC For Dummies: A simplified guide to understanding the PowerPC Instruction Set

[JimmyKazakhstan]

Thanks!
Believe it or not though, I still have a few more questions lol.

1. 

Code:

The halfword at the Effective Address is loaded in the lower 16 bits of rD. The remaining bits in rD are filled with a copy of the most significant bit of the loaded halfword.

What does "the most significant bit" mean?


2. 

Code:

Indexed: No use of VALUE, instead another Source Register is used for the Effective Address calculation

What would "With Update And Indexed" mean in this case? like with lwzux


3. 

Code:

Btw the Broadway manual (from what ive seen)

What manual are you reading? I've seen about 20 different ones at this point and they all have mostly different definitions for instructions, is there a "main" one?


4.

Code:

The definitions are not technically sound if that makes sense. There's other purposes for the use of OR and AND.

I referenced this thread when I wrote part of this, did I misunderstand what you wrote?

4.5

Code:

That's because every bit in a not instruction gets flipped.

Specifically, the person who told me about the not instruction said that it flips the value in a register, I just thought that meant making it negative.


5. 

Code:

"Check if a register holds a 32-Bit value"

I would rename this as this can mean checking if anything is present in the upper 16 bits of a register.

Rename it to something like "Executing a comparison on a register with a value exceeding the 16-bit signed range"

Not a question but I just wanted to say, Yeah, you're right. Although I'm leaving it as it is because I'm trying to get too technical on the page so that slow learners (like myself) don't get too confused by the terms.


6. 

Code:

Btw this actually won't work for your example on the site since your 32 bit value originated from r0

Also, don't use r1 for examples unless its for stack related stuff, as r1 is specifically designed to be the stack pointer in PPC.

Also not a question, just wanted to clarify. I'm using r0 and r1 for example purposes, I got a bit of a headache when I was trying to learn some of the instructions at first because of the register ranges (ex: r4, r22, r11) etc. I've just found it easier to use r0 and r1 as examples.

Thanks for taking the time to answer all of these btw. Most people would've gotten annoyed by the amount of questions I ask.