Lecturer's notes for CS210 Part 2, lecture 2, 20Apr07

Here are my notes for the lecture on Tuesday, 20Mar07.  I apologize that I was unable to
make my slides available in class.  I have put them up also, but they are not entirely
appropriate, since I adapted to the circumstances and changed my lecture topic somewhat.

You are responsible for all material that I cover in lectures and include in my slides and
notes.  Regarding additional reading material for part 2 of CS210, you are responsible for
the first 13 chapters of the lecture notes entitled, "The Alpha Computer Architecture," by
Dr. Bruce Hutton.  Most of my lecture material is covered in these notes, but not in the
same order.

Most of my lecture material for this week (lectures 2-4) is based on chapter 2 of the
notes.

You should read chapter 1 soon.  Don't worry about all the details.  I will assume you have
read it for my lectures, but the things I don't mention will not show up on the test or
exam--test and exam questions will have been covered in the lectures.


The Alpha architecture

Digital Equipment Corporation (DEC--once the second largest computer manufacturer in the
world) designed the Alpha as a replacement for the highly successful VAX introduced in 1976
(itself a replacement for the highly successful PDP-11 stemming from the 1960s).
Unfortunately, the Alpha architecture, while elegant in design and very fast, arrived too
late to market, and never captured a significant share.  DEC was bought by Compaq in 1998,
and rights to the Alpha were sold to Intel in 2001.  No new versions have emerged since
that time, and none are expected, though many would like to see it revived.

The Alpha was designed with the goal of lasting 25 years.  While the architecture likely
will be viable 25 years after its introduction, issues other than the architecture resulted
in its early demise.

Versions announced:
	21064 (EV-4): 1992
	21164 (EV-5): 1994
	21264 (EV-6): 1998
	21364 (EV-7): 2002

Saliant features of the Alpha architecture

Four principal kinds of instructions:
1. Arithmetic/Logical
2. Control
3. Memory: Load & Store
4. Special

1.  "Assignment" functions: arithmetic/logical:
	add, sub, mul, shift, and, or, not, invert

Three operands: 2 source, one destination

Example: add A, B, C

What if result is not representable (can that happen?)?  What should happen?
Overflow!

Special case: multiply: result may be twice as long as multiplier/multiplicand

Arithmetic

Add	(Addl, S4Addl, S8addl)
Sub	(Subl, Subq)
Mul	(Mull/Mulq x Umull/Umulq)
(No divide)