1. The Network Architecture of the Connection Machine CM-5 Charles E. Leiserson et al (Thinking Machines Corporation) Presented by Eric Carty-Fickes 1/28/04

2. major themes of CM-5 good performance (measured how?) ease of use (by programmers), flexibility  let programmer access nonpriveleged functions  do not involve OS if possible availability, reliability  use commodity parts and same part when possible – economy of mechanism split system into three separate networks (data, control, diagnostic)

3. network interface same interface for data and control networks provides context switching capability, makes processor save state interface appears as memory-mapped FIFO registers  protection enforced by processor users access relative processor addresses only; easy protection and error checking users unaware of network topology

4. data network fat-tree architecture used  keeps local traffic separate  can be adapted to various bandwidth schemes  keeps traffic balanced  claimed near-optimal data routing modified fat-tree uses two input and two output FIFO's to guarantee no deadlock variable-length packets (fixed for control) bandwidth scales linearly to 16,384 nodes

5. network protection flow control sent to message originator to protect buffers central clock synchronizes everything (good idea?) messages tagged with routing and processing info plus error check errors traced to origin (how many simultaneous errors detected/masked?) all-fall-down mode saves in-flight messages in random nodes

6. control network synchronizes processing nodes checks contract between processors and data network, reports errors hybrid MIMD architecture  combines SIMD's broadcasting with ability to run different parts of code barrier synchronization = line of code all processors must reach before continuing  improved with split-phase barriers broadcast = individual processors send out mass interrupts, code, data, etc. combining = select sets of nodes (only certain functions available) Kirchoff's law for messages assures at least no pair of messages lost

7. diagnostic network goal of functionality independence, use JTAG individual chips and collections can be tested network tree inherently self-testing hierarchy

8. Questions are there any errors, glaring or minor, that you can see with CM-5? do you really agree with the authors that it is okay to allow a user to cause deadlock?  should there be a check in place to prevent it?  might it not prevent an error in the network from being detected? would CM-5 really work just as well as technology progressed?