PREF - MIPS instruction reference

prefPrefetch 
Hints that the data at address ($t2 + offset) will be needed soon, so the hardware can begin moving it into cache.
Forms  pref , ()  
Operands imm5 An unsigned 5-bit immediate, 0 to 31, used for values such as a shift count. 
imm16 A signed 16-bit immediate, -32768 to 32767. 
$t2 Any general-purpose register, $0 to $31, using its numeric or named spelling, such as $8 or $t0 ($zero is $0; $ra is $31). 
The first operand is the hint type. A prefetch is only ever a hint and never changes what a program computes; this simulator has no cache, so it does nothing. It is accepted so that compiler output assembles unchanged.
 .data
.align 2
value: .word 42
.text
# Provide a valid address as a prefetch hint; inspect memory value remains 42.
la $t0, value
pref 0, 0($t0)