Electrical computers and digital processing systems: processing – Processing architecture – Long instruction word
Patent
1998-04-22
2000-02-15
Coleman, Eric
Electrical computers and digital processing systems: processing
Processing architecture
Long instruction word
712215, G06F 938
Patent
active
060264799
ABSTRACT:
A CPU having a cluster VLIW architecture is shown which operates in both a high instruction level parallelism (ILP) mode and a low ILP mode. In high ILP mode, the CPU executes wide instruction words using all operational clusters of the CPU and all of a main instruction cache and main data cache of the CPU are accessible to a high ILP task. The CPU also includes a mini-instruction cache, a mini-instruction register and a mini-data cache which are inactive during high ILP mode. An instruction level controller in the CPU receives a low ILP signal, such as an interrupt or function call to a low ILP routine, and switches to low ILP mode. In low ILP mode, the main instruction cache and main data cache are deactivated to preserve their contents. At the same time, a predetermined cluster remains active while the remaining clusters are also deactivated. The low ILP task executes instructions from the mini-instruction cache which are input to the predetermined cluster through the mini-instruction register. The mini-data cache stores operands for the low ILP task. The separate mini-instruction cache and mini-data cache along with the use of only the predetermined cluster minimizes the pollution of the main instruction and data caches, as well as pollution of register files in the deactivated clusters, with regard to a task executing in high ILP mode.
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Joseph A. Fisher, Paolo Faraboschi and Giuseppe Desoli; Hewlett-Packard Laboratories Cambridge, 1 Maine Street, Cambridge, MA 02142; "Custom-Fit Processors: Letting Applications Define Architectures"; 29th Annual IEEE/ACM International Symposium on Microarchitecture; Dec. 2-4, 1996, Paris, France.
Emerson Paul G.
Faraboschi Paolo
Fisher Joseph A.
Raje Prasad A.
Coleman Eric
Hewlett--Packard Company
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