In current processors, the cache controller, which contains the cache directory and other logic such as tag comparators, is active for each instruction fetch and is responsible for 20-25% of the power consumed in the Icache. Reducing the power consumed by the cache controller is important for low power I-cache design. We present three a r chitectural modications, which in concert, allow us to reduce the cache controller activity to less than 2% for most applications. The rst modication involves comparing cache tags for only those instructions that result in fetches from a new cache block. The second modication involves the tagging of those branches that cause instructions to be fetched f r om a new cache block. The third m o dication involves augmenting the I-cache with a small on-chip memory called the S-cache. The most frequently executed b asic blocks of code are statically allocated to the S-cache before p r ogram execution. We present empirical data to show the eect that these modications have on the cache controller activity.

No abstract

This paper evaluates the impact of transient errors in the operating system of a COTS-based system (CETIA board with two PowerPC 750 processors running LynxOS) and quantifies their effects at both the OS and at the application level. The study has been conducted using a Software-Implemented Fault Injection tool (Xception) and both realistic programs and synthetic workloads (to focus on specific OS features) have been used. The results provide a comprehensive picture of the impact of faults on LynxOS key features (process scheduling and the most frequent system calls), data integrity, error propagation, application termination, and correctness of application results.

No abstract

P u b lic r e p o r tin g b u r o e n l o r t h is c o lle c tio n o f in fo r m a tio n is e s tim a te d to a v e r a g e 1 h o u r p e r r e s p o n s e , in c lu d in g t h e t im e to r r e v ie w in g in s tr u c tio n s , s e a r c h in g e x is tin g d a t a s o u r c e s , g a th e r in g a n d m a m ta in n g t h e d a t a n e e d e d , a n d c o m p le tin g a n d r e v ie w in g t h e c o lle c tio n o f in fo r m a tio n . S e n d c o m m e n t r e g a r d in g t h is b u r d e n e s t im a te s o r a n y o t h e r a s p e c t o f t h is c o lle c tio n o f in fo r m a tio n , s i d u d in g s u g g e s tio n s t o r r e d u c in g th is b u r d e n , t o W a s h in g to n H e a d q u a r t e r s S e r v ic e s . D ir e c t o r a t e f o r « f o r m a tio nO p e r a t io n s a n d R e p o r ts . 1 2 1 5 J e f f e r s o n D a v is H ig h w a y . S u it e 1 2 0 4 . A r lin g to n . V A 2 2 2 0 2 -4 3 0 2 . a n d to t h e O ff ic e o f M a n a g e m e n t a n d B u d g e t. P a p e r w o r k R e d u c tio n P r o je c t ( 0 7 0 4 -0 1 8 8 ) . W a s h in g t o n . D C 2 0 5 0 3 . . AGENCY USE ONLY (Leave blank)2. REPORT DATE A p r i l 2 0 0 2 REPORT TYPE AND DATES COVERED TITLE AND SUBTITLE 5. FUNDING NUMBERSAn E x p e r i m e n t a l E v a l u a t i o n o f t h e REE S IF T E n v i r o n m e n t f o r S p a c e b o r n e A p p l i c a t i o n s AUTHOR(S)K . W h i s n a n t , R . K . I y e r , Z . K a l b a r c z y k , P . J o n e s PERFORMING ORGANIZATION NAMES(S) AND ADDRESS(ES)COORDINATED SCIENCE LABORATORY 1 3 0 8 W. MAIN S T . URBANA, I L 6 1 8 0 1 SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING / MONITORING AGENCY REPORT NUMBER SUPPLEMENTARY NOTES 12a. DISTRIBUTION / AVAILABILITY STATEMENTApproved for public release; distribution unlimited. b. DISTRIBUTION CODE ABSTRACT (Maximum 200 words)This paper presents an experimental evaluation of a software-implemented fault tolerance (SIFT) environ ment built around a set of self-checking processes called ARMORs running on different machines that provide error detection and recovery services to themselves and to spaceborne scientific applications. The experiments are split into three groups of error injections, with each group successively stressing the SIFT error detection and recovery more than the previous group. The results show that the SIFT environment adds negligible overhead to the application during failure-free runs. Only 28 cases from over 28,000 error injections were observed in which either the application failed to start or the SIFT environment failed to recognize that the application had completed. Further investigations showed that assertions within the SIFT processescoupled with object-based incremental checkpointingwere effective in preventing system failures by protecting dynamic data within the SIFT processes. SUBJECT TERMS f a u l t i n j e c t i o n , d i s t r i b u t e d c o m p u t in g , s o f t w a r eim p le m e n t e d f a u l t t o l e r a n c e NUMBER IF PAGES Abstract Few distributed software-impleme...