APE100 project
This document describes a parallel processor for large scale scientific computations. This machine is based on the experience acquired with the APE computer. It is a fine grained SIMD processor, delivering a peak speed higher than 100 GFlop. This performance is, for instance, required for high precision computations in Quantum Chromo Dynamics [QCD]. The system and hardware architectures are described.
APE100 Architecture
APE100 is a SIMD (Single Instruction Multiple Data) parallel computer with a tridimensional architecture based on a cubic mesh of nodes. Each processing node is connected to its six nearest neighboursin all three space dimensions. Periodic boundary conditions are used to wrap around the mesh. The main advantage of this simple structure is modularity. The configuration of APE100 is scalable from 8 to 2048 nodes.
Each node is composed of a single precision 32 bits IEEE-754 floating point processor, (the MAD), a 4 (or 16) Mbytes RAM bank and the logic for node-to-node communication. Parallel processing on APE is limited to operations on floating point numbers. Each node is capable of 50 Mflop so that the complete configuration has a performance of 100Gflop. There is a Controller for each group of 128 nodes and all the Controllers execute exactly the same code.
The Controllers are based on a scalar processor named Z-CPU which executes the user program, all integer operations and delivers the microcode and the data addressing to the nodes. The Z-CPU has its own data memory, program memory and registers.
The APE100 synchronous core (i.e. the Z-CPU's and the nodes described above) is connected to a host computer through an asynchronous interface, called AI (Asynchronous Interface), based on a network of transputers which act as front end. The user program runs on the synchronous core.
This asynchronous interface is able to access all the resources of APE100: control registers and memory banks of the synchronous core as well as the parallel mass storage system. The host communicates with the AI by using transputer links. The system code running on the AI is able to convert requests coming from the host (on the transputer links) into operations on the APE100 machine, as well as to serve interrupts arising from the synchronous machine. Most part of the system software runs on the host computer while the real time kernel of the operating system runs on the AI.
This below is a sensitive map showing the overall synchronous core of a Ape installation.
