Movsw/Movsd

Unknown

Shouldn't this...

mov cx, 160

rep movsw

...be slower than this

mov cx,80

rep movsd

I have tried them both but the time is equal. Why?

Thanks in advance

/Distance

Unknown

: Shouldn't this...

: mov cx, 160

: rep movsw

: ...be slower than this

: mov cx,80

: rep movsd

: I have tried them both but the time is equal. Why?

1. Because you were moving through a 16-bit port (for example an old isa video card);

2. Because you were moving 2 (or even 1) byte aligned, that is, you where moving between addresses that were not a multiple of 4. Actually, iirc, moving segment-aligned (16-bytes aligned) can give you an bonus speed-increase;

3. Because your timing is off? I hope you did this move a LOT of times :-)

Greetz,

The Watcher