buzzword
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buzzword [2015/02/11 19:20] rachata |
buzzword [2015/02/16 19:16] rachata |
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| - | ===== Lecture 11 (2/11 Mon.) ===== | + | ===== Lecture 11 (2/11 Wed.) ===== |
| * Geometric GHR length for branch prediction | * Geometric GHR length for branch prediction | ||
| * Perceptron branch predictor | * Perceptron branch predictor | ||
| - | * Multi-cycle executions (Different functional units take different number of cycles) | + | * Multi-cycle executions (Different functional units take different number of cycles) |
| * Instructions can retire out-of-order | * Instructions can retire out-of-order | ||
| * How to deal with this case? Stall? Throw exceptions if there are problems? | * How to deal with this case? Stall? Throw exceptions if there are problems? | ||
| * Exceptions and Interrupts | * Exceptions and Interrupts | ||
| * When they are handled? | * When they are handled? | ||
| - | * Why are some interrupts should be handled right away? | + | * Why are some interrupts should be handled right away? |
| * Precise exception | * Precise exception | ||
| * arch. state should be consistent before handling the exception/interrupts | * arch. state should be consistent before handling the exception/interrupts | ||
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| * Easier to restart the processes | * Easier to restart the processes | ||
| * How to ensure precise exception? | * How to ensure precise exception? | ||
| - | * Tradeoffs between each method | + | * Tradeoffs between each method |
| * Reorder buffer | * Reorder buffer | ||
| * Reorder results before they are visible to the arch. state | * Reorder results before they are visible to the arch. state | ||
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| * Where to get the value from (forwarding path? reorder buffer?) | * Where to get the value from (forwarding path? reorder buffer?) | ||
| * Extra logic to check where the youngest instructions/value is | * Extra logic to check where the youngest instructions/value is | ||
| - | * Content addressible search | + | * Content addressible search (CAM) |
| * A lot of comparators | * A lot of comparators | ||
| * Different ways to simplify the reorder buffer | * Different ways to simplify the reorder buffer | ||
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| * Future file (commonly used, along with reorder buffer) | * Future file (commonly used, along with reorder buffer) | ||
| * Keep two set of register files | * Keep two set of register files | ||
| - | * An updated value (Speculative), called fiture file | + | * An updated value (Speculative), called future file |
| * A backup value (to restore the state quickly | * A backup value (to restore the state quickly | ||
| * Double the cost of the regfile, but reduce the area as you don't have to use a content addressible memory (compared to ROB alone) | * Double the cost of the regfile, but reduce the area as you don't have to use a content addressible memory (compared to ROB alone) | ||
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| * Checkpointing | * Checkpointing | ||
| * Advantages? | * Advantages? | ||
| + | |||
| + | ===== Lecture 12 (2/13 Fri.) ===== | ||
| + | |||
| + | * Renaming | ||
| + | * Register renaming table | ||
| + | * Predictor (branch predictor, cache line predictor ...) | ||
| + | * Power budget (and its importance) | ||
| + | * Architectural state, precise state | ||
| + | * Memory dependence is known dynamically | ||
| + | * Register state is not shared across threads/processors | ||
| + | * Memory state is shared across threads/processors | ||
| + | * How to maintain speculative memory states | ||
| + | * Write buffers (helps simplify the process of checking the reorder buffer) | ||
| + | * Overall OoO mechanism | ||
| + | * What are other ways of eliminating dispatch stalls | ||
| + | * Dispatch when the sources are ready | ||
| + | * Retired instructions make the source available | ||
| + | * Register renaming | ||
| + | * Reservation station | ||
| + | * What goes into the reservation station | ||
| + | * Tags required in the reservation station | ||
| + | * Tomasulo's algorithm | ||
| + | * Without precise exception, OoO is hard to debug | ||
| + | * Arch. register ID | ||
| + | * Examples in the slides | ||
| + | * Slides 28 --> register renaming | ||
| + | * Slides 30-35 --> Exercise (also on the board) | ||
| + | * This will be usefull for the midterm | ||
| + | * Register aliasing table | ||
| + | * Broadcasting tags | ||
| + | * Using dataflow | ||
| + | |||
| + | |||
| + | ===== Lecture 13 (2/16 Mon.) ===== | ||
| + | |||
| + | * OoO --> Restricted Dataflow | ||
| + | * Extracting parallelism | ||
| + | * What are the bottlenecks? | ||
| + | * Issue width | ||
| + | * Dispatch width | ||
| + | * Parallelism in the program | ||
| + | * What does it mean to be restricted data flow | ||
| + | * Still visible as a Von Neumann model | ||
| + | * Where does the efficiency come from? | ||
| + | * Size of the scheduling windors/reorder buffer. Tradeoffs? What make sense? | ||
| + | * Load/store handling | ||
| + | * Would like to schedule them out of order, but make them visible in-order | ||
| + | * When do you schedule the load/store instructions? | ||
| + | * Can we predict if load/store are dependent? | ||
| + | * This is one of the most complex structure of the load/store handling | ||
| + | * What information can be used to predict these load/store optimization? | ||
| + | * Centralized vs. distributed? What are the tradeoffs? | ||
| + | * How to handle when there is a misprediction/recovery | ||
| + | * OoO + branch prediction? | ||
| + | * Speculatively update the history register | ||
| + | * When do you update the GHR? | ||
| + | * Token dataflow arch. | ||
| + | * What are tokens? | ||
| + | * How to match tokens | ||
| + | * Tagged token dataflow arch. | ||
| + | * What are the tradeoffs? | ||
| + | * Difficulties? | ||
buzzword.txt · Last modified: 2015/04/27 18:20 by rachata
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