Uit nieuwe info die Hans de Vries van Chip-Architect.com op het Microprocessor Forum wist op te pikken, blijkt dat de Pentium 4 dubbeler gepompt is dan aanvankelijk werd aangenomen . Niet alleen de ALU's, maar ook de schedulers, integer register files en de load/store address generators lopen op een dubbele frequentie. Om dit verhaal ook voor normale stervelingen geloofwaardig te maken, heeft Intel's marketing afdeling de pipeline omgedoopt tot 'Rapid Execution Engine'. Hier heb je eerder al het een en ander over kunnen lezen.
De trace cache vormt overigens een bottleneck omdat-ie niet meer dan één load en/of store address per klokcycles accepteert:
The biggest surprise during today's speech of Intels Michael Upton at the Microprocessor Forum in the Fairmount hotel in San Jose is without a doubt the disclosure that not only the Integer ALU but also several other units run at double the processor frequency. Starting with the two schedulers for the ALU's. Each double pumped ALU appears to have it's own scheduler. The entire integer register file which contains the renamed and real registers runs at the double frequency. Also the load and store address generators are included in what is called the Rapid Execution Engine since the autumn IDF. This is in contrast with earlier presentations which only mentioned the "double pumped" ALU.[...] This newly disclosed information means that 9 out of 20 pipeline stages contain double frequency components, much more then the 2 previously assumed. The fact that also the Address Generators run at double the frequency remains a bit puzzling since the 8 kByte L1 data cache runs at the normal frequency and won't accept anymore then 1 load and/or store address per cycle.
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