On Nov 24, 2006, at 6:49 PM, William Robb wrote:

>> 64 bit software is likely to be slower, (which goes for the OS as
>> well), when compared with 32 bit software on any given platform.
>
> Now that is interesting.
> Naturally, I thought that going 64 bit would give me a speed increase.
> Would you elaborate on this please?

There are a lot of misconceptions about what going to 64bit means and  
this is one of them.

At the present time, there are very few solutions that benefit from  
64bit instructions and 64bit data. Processing huge datasets (I mean  
REALLY huge ... Gigabytes of data at a time) are one thing, but  
processing a hundred or two 20 Mbyte RAW files hardly fits into that  
class.

Moving to 64bit processing means:
- instructions that are twice the length with associated operands  
that are
    correspondingly larger too.
- data registers that are twice the size

Just the IO required for the above means that a 64bit processor  
operating at the same bus speed and same clock rate as a 32bit system  
will mean slower overall operations if the data being processed does  
not require 64 bit resolution. Most things being processed do not.

FYI: Not even using current or fastest of its generation hardware,  
the Power Macintosh G5 2Ghz DP with 3G of RAM and a fast 500G drive,  
running Photoshop CS2 and Camera Raw, will RAW convert 100 Pentax  
*ist DS PEF files (with all RAW conversion parameters preset) direct  
to full resolution, minimum compression JPEG images in less than 4  
minutes. I've timed this several times ... I've often times thrown  
300 RAW files at ACR and told it to process them all to PSD files. By  
the time I get back from the kitchen with a cup of tea, they're done.  
It's a 64bit processor but Mac OS X v10.4.x and Photoshop is still a  
32bit OS and Application. Doesn't seem to phase anything ... it's  
very fast.

Godfrey


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