Cutting-Edge Computer Architectures (ACA)

Upon finishing this subject, students should be able to:
-  Understand the functionality of a simple segmented processor and implement one at block level with a cache hierarchy (instructions and data) and with support for paged virtual memory.
-  Understand the functionality of a simple segmented processor and implement one at block level with precise exceptions and support for external interrupts.
-  Understand the functionality and implement cutting-edge performance improvement techniques for segmented processors at block level, including superscalar execution, out-of-order execution and multi-threading techniques.
-  Understand the functionality and implement at block level vectorial processing technique, applied in particular to supporting multimedia programs.
-  Understand the functionality of special-purpose processors such as DSPs or 3D graphics accelerator cards.

Knowledges

1. Memory hierarchy, store instruction ordering, write-to-cache techniques, write buffer, merge buffer, cache flush.
   
   
   
   Store-load dependencies in a pipeline with two write stages.
2. TLB (translation look-aside buffer) concept, Operating System support for virtual paging memory, and fault management in the TLB.
3. Precise (and imprecise) exceptions. Interruption. The impact of exceptions and interruptions in the segmentation process. Precise State recovery. Ordering exceptions. Implementation of vector interruptions.
4. Jump prediction - concept. Two-bit predictors with history registers. Integration of the predictor in the segmented pipeline. Predictor training. Error recovery
5. Out-of-order execution ("complete out of order" and "initiate and complete out of order" variants). Re-order Buffer and Future File technique (Smith & Plezskun, 1985). Recovering Precise State in cases of exception and interruption.
6. Renumbering registers - concept. Integrating pipeline renaming. Reorder Buffer integration. Recovering the rename table in cases of exception.
7. Selection (pick & wake-up) of instructions within an instruction window. Dependence control among registers. Control dependencies among memory instructions.
8. Super-scalar execution. Fetching multiple instructions within a clock cycle. Prerequisites for simultaneously executing two instructions.
9. Multithread execution. Types of multithreading: fine-grain, switch-on-event, simultaneous multithreading. Chip-Multiprocessor. Incorporating two threads for renaming in an out-of-order segmented pipeline.
10. Vectorial execution. Advantages and drawbacks of vectorial execution. Specific memory access instructions (Strides and Gather/Scatter). Datapath partitioning in lanes. Memory organisation by vectoral access.
11. The concept behind specific purpose processors: embedded, DSP, and 3D graphic processors. Example of the workings of a 3D graphic processor.

Abilities

1. Mastery of LogicWorks 4 and LogicWorks 5 simulators. Ability to create a model of the processors presented and simulate their operation.
2. Use verilog as a hardware modelling language in order to model the processors presented in class.

Competences

1. Ability to solve problems through the application of scientific and engineering methods.
2. Ability to create and use models of reality.
3. Ability to design and carry out experiments and analyse the results.
4. Know-how to apply the solution cycle to common scientific and engineering problems: specification, coming with ideas and alternatives, design solution strategies, carrying out the strategy, validation, interpretation and evaluation of results. Ability to analyse the process on completion.
5. Ability to take take decisions when faced with uncertainty or contradictory requirements.
6. Initiative: Resolution, knowing how to take decisions and how to act in order to solve a problem.
7. Ability to work effectively in large groups to solve complex problems.
8. Ability to set up and organise either a uni- or multi-disciplinary group to tackle a complex project.
9. Leadership.
10. Ability to understand and constructively criticise presentations given by others.
11. Assume responsibility for one"s own work.

Theory and Problems: Common problems (lecture)







Laboratory:







Students will collectively undertake a practical session involving implementing a simple 5, 6, or 7-stage multi-cyclic, superscalar processor incorporating jump prediction. The processor must include a cache hierarchy (instructions and data), and must share data with a disk controller through a bus and main memory.







It should be stressed that all students will work on the same processor. In other words, students will work in groups and by stages but must assemble all of the processor components to produce a working whole. It goes without saying that this form of learning is both extremely effective and highly motivating. Students tackle a real project in which the various groups have to communicate with one another and reach agreement on an implementation that is straightforward for all concerned. Furthermore, the teacher will prevent over-simplified implementation being adopted to ensure that the whole process is as realistic as possible.







The course stresses putting theory into practice. The first four weeks of the course stress theory classes, and include some tasks. Students acquire with the knowledge needed to make an early start on the practical work.







Lab sessions take place in either the PC classroom or in a conventional classroom. In the former case, students implement specific aspects of the practical work and debug circuits. These sessions are particularly useful when it comes to drawing together the various processor stages.



In the latter case, the sessions cover processor design, in which the various groups discuss the precise processor implementation under the teacher"s supervision.

NP1 = Practice Grade - First Submission
NP2 = Practice Grade - Second Submission
NE = Exam grade

Final Grade = 0.4 NE + 0.2 NP1 + 0.4 NP2

The first piece of practical work will be submitted before the course halfway point to ensure that the basic processor components work properly and to check that students grasp the theoretical concepts and are able to put them into practice.

• David A. Patterson, John L. Hennessy Computer Organization and Design, 3rd Edition, Morgan Kaufmann, 1997.

• Mike L. Johnson Superscalar Microprocessor Design, Prentice Hall, 1991.
• Bruce D. Shriver, Bennett Smith The Anatomy of a high-performance microprocessor : a systems perspective, IEEE Computer Society Press, 1998.
• Capilano Computing Systems, Ltd LogicWorks 5 : interactive circuit design software, Prentice Hall, 2004.

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