ISA Flashcards
what is the difference between GPR and special purpose registers
GPR software controlled and accessible in typical collection is register file
special purpose register - has a special role and only accessible by special instructions
define address space
range of accessible adresses
define addressability
how many bits do we need to access elements of memory
define granularity
what does each address refer to
i.e
byte addressible if each element is 8 bits
define alignment
for an n byte word at address x
x mod n =0
define endianness
order we store the bytes
little - first stored at lower memory
big - last stored at lower memory
define fixed length encoding
each instruction has the same length
define variable length encoding
each instruction has its own length
what is an example of an instruction that uses R type encoding and explain it
add
bits 0-5 function
6-10 shift
11-15 register destination
16-20 target register
21-25 register source
26-31 opcode (what instruction type i.e R type)
what is an example of an instruction that uses I type encoding and explain it
Addi
target register <- source + immediate
bits 0-15 - immediate
16-20 - target register
21-25 - register source
26-30 - opcode (again type I type)
what is an example of an instruction that uses J type encoding and explain it
jump instructions
0-25 - address
26-31 - opcode
32 bits byte addressible
what is a memory memory architecture
all operands held in memory
what is a register memory architecture
some operands in memory some in registers
what is register register memory aka load store memoyr
operands are registers and ISA has instructions to move thinsg into registers or write to memory
