Re: Version after Version

"Marc Rohloff" <marcrohloff_ng@xxxxxxxxxxx> wrote in message

>> Not if you need speed.
>> When written to take advantage of the 64-bit wide data path, applications
>> can become twice as fast.
>
> Not true.
> a) A 64 bit processor is not twice as fast as a 32 bit processor.

You should read my sentence again.
"
When written to take advantage of the 64-bit wide data path, applications
can become twice as fast."

of course, when doing operations 64-bits at a time instead of 32 bits at a
time, the algorithm and its execution becomes (more than) twice as fast.
This is elementary with 64 bit CPU's and if you do not understand it then I
recommend you do a little experiment. Write a file
compressor/decryptor/encoder/whatever. It works in-memory. First write it
using 32-bit arithmetic, then using optimized algorithm for 64-bit
arithmetic, making sure you load 64 bits at a time (using MMX, if you have
no true 64-bit CPU), operate on 64 bits at a time and store 64 bits at a
time.

That your favorite game doesn't run twice as fast on a 64-bit CPU, doesn't
mean they aren't twice as fast with 64-bit algorithms!
In fact, due to less bookkeeping, they are about three times faster in that
repect, but you loose that 33% again due to mamory bandwidth issues etc.


> b) Since pointers become wider data and code size will increase
> significantly requiring more RAM to perform the same task, more memory
> transfers and more processor cycles.

Nope, that is utter nonsense. Only try when running 32-bit code on a 64-bit
CPU.
64-bit code is much *smaller* than 32-bit code, because you need three times
less instructions to do the same thing, because you operate on 64-bit data
instead of 32-bit data. I have written a 64-bit antialias routine and not
only was it much faster on a 64-bit CPU, the code also was much smaller
because I worked on 3 RGB triplets in a single register.



.

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