rather unfortunate article on Mac

Bari Ari bari at onelabs.com
Fri Feb 1 00:32:43 EST 2002


Art Edwards wrote:

>On Thu, Jan 31, 2002 at 08:48:11PM -0600, Bari Ari wrote:
>
>>We looked at building some very dense clusters using the G4s. The 
>>floating point performance is great (15Gflops peak) as well as the raw 
>>performance vs. power consumption (21watts at 1GHz). The main drawbacks are 
>>price of the CPUs (though the new 7455s are only $125/10k for the 800MHz 
>>versions), lack of support from Motorola and lack of any decent 
>>clustering software such as Scyld.
>>
>
>Is it still true that the vector processors only handle single precision
>floating point?
>
I don't really follow them too closely anymore, but a quick check of the 
datasheet mentions:

MPC7455 and MPC7445 microprocessors feature a high-frequency superscalar 
G4 core capable of issuing four instructions per clock cycle (three 
instructions + branch) into eleven independent execution units:

    * Four integer units (3 simple + 1 complex)
    * Double-precision floating-point unit
    * Four AltiVec units (simple, complex, floating, and permute)
    * Load/store unit
    * Branch processing unit

AltiVec technology operations are performed on multiple data elements by 
a single instruction. This is
often referred to as SIMD (single instructions, multiple data) parallel 
processing. AltiVec technology offers
support for:

 16-way parallelism for 8-bit signed and unsigned integers and characters
 8-way parallelism for 16-bit signed and unsigned integers
 4-way parallelism for 32-bit signed and unsigned integers and IEEE 
floating point numbers

Bari



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