To: File alphaspectrom\architecture1.wpd

From: Jon Hagen

Date: June 2, 2003

Subject: Alfa back-end architechture

The signals from the seven feeds are independent throughout the data-taking process and, except for map making, throughout subsequent data analysis. It therefore seems obvious to use seven separate processors, each with its own final data storage.

Each of the seven systems would have its own pair of A-to-Ds to sample the two polarizations. These digitizers could be in their own chassis, remote from the processor, with serial fiber optic connections to ensure that processor-generated noise is not fed back to the digitizers.

The main processing would be done on a board containing between 1 and 6 Altera or Xilinx FPGA chips. These chips would be loaded at run time with 'cores' and glue code appropriate for the observation: polyphase dft filtering or 'pipelined frequency transform' ( PFT) filtering.

The seven FPGA boards would be contained within seven Linux PCs (or within 14 PCs, if output data rates cannot be handled with 7 PCs).

Piggybacking would require either:

a. sufficient room in the FPGAs for simultaneous processes or

b. multiple FPGA boards in each PC or

c. multiple PC septets or

d. WAAPs.