[Cs35101] required to bring picture ids to exam, exam 3 topics revised, arrive on time, bit-prediction

[Dianne Foreback]

Dear Computer Architecture Class:

Your picture ids are required to take the final exam.

The exam is a bit longer than previous exams so arrive on time.  The exam
begins at 7:45 a.m. and ends at 10:00 a.m. (early morning).  We only have
the room until 10 a.m. Additional time is not given.   That being written,
we are in for some snow, so give yourself ample driving time to allot for
safe driving.

Exam 3 topics on our website are revised.  We did not cover exceptions,
section 4.9, so you may skip this.

1-bit and 2-bit branch prediction question posed by a fellow student:
When using a single bit for prediction, the most recent past history is
considered to predict if the branch should be taken or the branch should be
not-taken.  For example, if the branch is taken and done so correctly, the
prediction bit is set to taken.  So, the next time a branching instruction
is encountered, the prediction will be to take the branch.  But, if
incorrect, the prediction bit is changed to not-taken.  Thus, after one
mistake, the prediction bit is changed.  This is helpful with a single for
loop when the branch is taken multiple times.  But, not so good with nested
loops.

Now, with 2-bit branch prediction, a prediction mistake must be made twice
before changing the prediction bit.  This is helpful with nested for
loops.  The state machine illustrates how two bits can be used to determine
if a prediction is incorrect twice in a row, in which case, the prediction
will change.

Best to all,
Dianne
_______________________________________________
Dr. Dianne Foreback, Assistant Professor
Department of Computer Science
Math and Computer Science Building (MSB) 266
P.O. Box 5190, Kent, Ohio 44242-0001, USA
Phone: 330.672.9064
Email: dforebac at kent.edu
_______________________________________________
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