[Ti] Will Apple drop its OS?

[Glenn L. Austin]

On Apr 6, 2006, at 9:11 PM, Chris Olson wrote:

> On Apr 6, 2006, at 10:12 PM, Glenn L. Austin wrote:
>
>> It's strange that you say that, since Mach was designed to run on  
>> CISC hardware
>
> Unlike IA32, PowerPC does not have a call or jmp instruction.   
> Execution flow is controlled by one of the many branch instructions.

And PowerPC doesn't have an instruction to get the current PC  
directly, to do that requires a branch to the next instruction saving  
the link register and a load of the link register into a general  
purpose register.  MachO (the native binary format for Mac OS X) uses  
PC-relative constants.  Yes, that's right, every reference to a  
constant requires a branch, which causes a flush of the instruction  
pipeline.

On the other hand, x86 has a direct "load relative to PC" instruction  
which doesn't flush the instruction pipeline -- so MachO is much more  
efficient.

NeXTStep was released on 68K and x86, and later ported to PPC as  
"Rhapsody" which became the core of Mac OS X.

I was at Apple during the NeXT integration.  And you were where...?

-- 
Glenn L. Austin <><
Computer Wizard and Race Car Driver
<glenn at austin-home.com>
<http://www.austin-home.com/glenn/>