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Re: [f-cpu] Are 8 bits SIMD mode usefull ?

On 09 Jan 2003 20:52:34 +0100
Antoine <antoine@rezo.net> wrote:

> 
> Hi,
> 
> Le ven 10/01/2003 à 21:37, nico a écrit :
> > Just a stupid question : is 8 bits integer mode usefull ?
> 
> I think so ;)
> 
> > "Char" C type are going to be 16 bits (unicode)
> 
> The most widely used encoding of unicode, UTF-8, is based on regular
> bytes (it's a variable length encoding backwards compatible with
> Ascii). That means both legacy character strings and unicode strings 
> will use byte operations. Protocol networks, compression formats will 
> also remain byte-based. And so on ;)
> 
> > Gimp use 16 bit per channel
> 
> I think that's false, that's even why Film Gimp exists (movie guys
> need more than 8 bits per channel and Gimp can't satisfy their needs).
> However even if Gimp can do 16 bits per channel, most images will
> still only require 8 bits per channel, leading to more compact
> representations and faster calculations (and less memory transfers
> ;-)).
> 
> Also if you think SIMD in stuff like GIMP, operations with 8-bit
> per channel will be twice faster than with 16-bit channel (because
> your registers have a fixed size and you can stuff twice more bytes
> than 16-bit integers into a register).
> 

Half the bandwith consumption but many more operations to avoid
overflow/underflow problems ! I beleive that GPU use float to avoid such
mess !

> Hey, if you wanna write an x86 emulator for F-CPU, you'll also need 
> bytes :-)))
> 

hugh.. !

> Regards
> 
> Antoine.
> 
> 
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