Denis Dowling wrote:
There are a couple of other "ports" on a PC that could be used for initial debugging. I have used a spare IDE channel as a general 8 bit IO port. In fact you can address up to 8 different ports per channel. A simple outb(b, 0x170) gets reflected on the port. This is dead easy to interface with. Connect a logic analyser or a small circuit and then just write to the port. Does not help if the IDE sits out on the PCI bus though.
The problem here is that IDE is going the way of the serial port as well. Maybe a SATA debug module is a way to go. I could spin a simple FPGA based card for output.
Another thought would be to tap the SMBus signals. These are routed to all memory DIMMS. With some careful soldering you can tap the signals off the DIMM to a logic analyser. The code can then just write to an unised i2c address
A debug card could also be designed the same form factor as a memory dimm. It could be placed into an unused memory slot to debug via the SMbus. This is easier than the SATA method to build.
copyright c 2006, patent pending
-Bari