On G5

While saving up for a G5 I have been intensively researching the capabilities of the new Apple systems. For a while I was wavering when the Athlon Fx was released, but that moment has passed. There has been a lot of controversy about the 64-bitness of the new G5 coupled with the Panther OSX release. Delving deeper into the matter reveals that the application space on the G5 runs in 32-bit mode to ensure backward compatibility. In other words, the applications are using a 32-bit address space. Other than this fact, the G5 is a true 64-bit processor in every respect. Being 64-bit is not the greatest aspect of the new G5 systems. In fact, the overall architecture changes, more pipeline stages, faster floating point operations, much faster bus, and faster memory controller are the true wins. The 64-bit architecture in itself is not dog food however. In fact, the number of approximate instructions per 64-bit operation between the G4 and G5 are striking: 


</tr>   <tr>        <td>shifts</td> <td>5 to 14</td> <td>1</td> </tr>   <tr>        <td>divide</td> <td>>100</td> <td>1</td>    </tr>   <tr>        <td>sqrt</td> <td>>20</td> <td>1</td>   </tr>   <tr>        <td>long->double</td> <td>>50</td> <td>3</td>   </tr>   <tr>        <td>double->long</td> <td>>50</td> <td>3</td>   </tr></table>



Amazing huh? Likewise, floating point operations have been showing 100% speedups over G4 implementations. Because the G4 was a 32-bit architecture, any 64-bit operation had to be split into two 32-bit units, operated upon, and combined again. This may not speed up your dragging and dropping (yet), but for workstation-esque tasks it will provide a world of difference at a similar or fraction of the cost of many comparable offerings from SGI, IBM, Alienware, Sun, and HP. If you’re looking for a huge boast over the G4 in number crunching, then by all means consider the G5; you will not be ripped off – it’s a workstation at a high-end desktop price. However, for general usage I would suggest going with the G4 based lines still available (and dropping in price daily). I myself am going with the G5 because I can use a speed boost in FP and long operations, and if I can’t then I will invent something that will.

-m

Operation G4 G5
load/store 2 1
add,sub,neg 2 1
and,or,xor,not 2 1
multiply 6 1
compare 1 to 12 1