Virtex-4 PCB design

Gerber files are like printouts. They were designed to run X/Y photo- plotters. There are a number of Gerber file viewers available on the web, some of them are free. It is also possible to generate a netlist from a set of Gerbers, but you won't have meaningful net names unless they were embedded in the files. It is unlikely that you can get back the design database from the Gerber files. This is a little like trying to get source code from a .bit file in an FPGA.

The .pho file extension (for photoplot) may indicate that the design database was PADS. AFAIK there is no common standard for filename extension of gerber files, although the file format itself is well defined (usually RS-274X).

I use a viewer from pentalogix called ViewmasterEZ, which is not free, but it is cheap. It allows editing of Gerber files as well as some rudimentary design-rule checking. This sort of tool is extremely useful if you design PCB's, because there is often a "disconnect" between the design database and the final deliverables for laminate fabrication. One of the other engineers here uses a package called Gerbtool (IIRC) and that one has more features including netlist generation.

HTH, Gabor