Hacking the Xbox

Chapter 8 - Reverse Engineering Xbox Security 129
In building the logging device, I had settled on using a Virtex-E FPGA
that was integrated into a board that I had previously built. However, the
one problem with using the Virtex-E FPGA is that the performance of
the FPGA (as specified in the databook) is insufficient to keep up with
the HyperTransport bus. Fortunately, FPGAs overclock well because
their manufacturing margin is very conservative, and because FPGA
performance is largely limited by signal propagation delays in the
configurable wiring fabric. As a result, some key performance-limiting
paths can be manually identified and compensated using soft delay lines
and selectively inverted clocks. The most performance sensitive blocks
can be hand-placed to optimize the delays, while the compiler and
Figure 8-6: Schematic of the HyperTransport tap board.