AArch64 / x86_64 Study Reflection

This post is going to cover my thoughts on the AArch64 / x86_64 architectures after studying them for a quiz I did on the previous Friday.


Some of the key aspects that stood out to me when studying these architectures includes their approach to registers and how they are coded through assembly language. 


In terms of how the registers were done what stuck out to me was that there a lot more than the 6502 chip I worked with in the past and that most of them were multi purpose. Regarding the quantity of registers AArch64 has 30 registers that are mostly usable and x86_64 has 16 registers that most can be used safely. In comparison, the 6502 chip I worked with only has 3. A great aspect to these two architectures is that all of these registers are multipurpose while the 6502 chip only has two registers that can increment numbers and only one that can add more than one number.


When it comes to programming those chips what surprised me was how similar it was to coding on a 6502. For instance, on the 6502 all optcodes worked by typing a 3 letter command and then feeding that command with a register, a address in memory, or with a hex or decimal number. On the AArch64 / x86_64 chips it works in the same way, the only difference is how numbers, addresses, and registers are referenced when feeding them into optcodes. Another quirk I found mainly between the two architectures I studied was how values were are transferred to registers. On the AArch64 a value would fed into a register from right to left (ex: add r0, r1, r2 | here the value from r1+ r2 would be fed into the register r0). While on x86_64 side it would be left or right (ex: add %r10, %r11 | here the values in r10 and r11 are added together and the result is stored in r11).


Overall after studying these architectures I feel a little less overwhelmed in trying them out as well as a little excited in programming the hardware I use everyday instead of the emulator of a really old chip.


References;
https://wiki.cdot.senecacollege.ca/wiki/AArch64_Register_and_Instruction_Quick_Start

https://wiki.cdot.senecacollege.ca/wiki/X86_64_Register_and_Instruction_Quick_Start