Stanford EE Computer Systems Colloquium

4:15PM, Wednesday, May 29, 2013
Skilling Auditorium, Stanford Campus

Drinking from the firehose
How the Mill CPU decodes 30+ instructions per cycle

Ivan Godard
Out-of-the-Box Computing
About the talk:

The military maxim amateurs study tactics, professionals study logistics applies to CPU architecture as well as to armies. Less than 10% of the area and power budget of modern high-end cores is devoted to real work by the functional units such as adders; the other 90% marshalls instructions and data for those units and figures out what to do next.

A large fraction of this logistic overhead comes from instruction fetch and decode. Instruction encoding has subtle and far reaching effects on performance and efficiency throughout a core; for example, the intractable encoding used by x86 instructions is why the x86 will never provide the performance/power of other architectures having friendlier encoding.

Some 80% of executed operations are in loops. A software-pipelined loop has instruction-level parallelism (ILP) bounded only by the number of functional units available and the ability to feed them. The limiting factor is often decode; few modern cores can decode more than four instructions per cycle, and none more than 10. The Mill is a new general-purpose CPU architecture that breaks this barrier; high-end Mill family members can fetch, decode, issue and execute over 30 instructions per cycle.

This talk explains the fetch and decode part of the Mill architecture.


Download the slides for this presentation. The slides are in Powerpoint (.pptx) format and require an appropriate viewer. A PDF version cannot be provided because the slides include dynamic animations and revealss which are not supported in PDF.

About the speaker:

Ivan Godard has designed, implemented or led the teams for 11 compilers for a variety of languages and targets, an operating system, an object-oriented database, and four instruction set architectures. He participated in the revision of Algol68 and is mentioned in its Report; was on the Green team that won the Ada language competition; designed the Mary family of system implementation languages; and was founding editor of the Machine Oriented Languages Bulletin. He is a Member Emeritus of IFIPS Working Group 2.4 (Implementation languages), and was a member of the committee that produced the IEEE and ISO floating-point standard 754-2011.

Ivan is currently CTO at Out-of-theBox Computing, a startup now emerging from stealth mode. OOTBC has developed the Mill, a clean-sheet rethink of general-purpose CPU architectures. The Mill is the subject of his talk today.

Contact information:

Ivan Godard
Out-of-the-Box Computing