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SubjectRe: Kernel Debugging Hardware
On May 12, Steven S. Dick wrote:

> I believe it would be possible for <$50 to make a small device that could
> sit on a serial port and look for kernel OOPS messages and record them
> so that they can be examined after a reboot.
> One possible implementation would use a serial eeprom and a pic chip
> as a ring buffer and controller. It could be set up to just remember
> the last several K of messages, or stop recording before overwriting
> the first OOPS it sees, or something like that.

good idea, I'd need it for better debuging of Xservers when the PC completely
locks up (and of course for kernel stuff too).

a few questions/remarks (not being too good in circuityr anymore):

- how many write cycles are possible for eeproms these days ? I remeber of some 10k cycles ?!
if this is still a limitation there would be no chance to log data online until
the system will crash (ok, it would be enough to record the oops once it happend
but that's usually not my subject)

what about using a 8k SRAM or similar ? using e.g. Tx etc. for power supply...
loosing data after power off is usually no big problem

- what about using a parallel port as interface ? while I already have
8 serial ports they are usually all bussy (and standard COM1/COM2 are
locked for mouse & modem...). pretty often printer ports are free.
being able to use both ser/par port would be great (more possible users...)

- I'd register only binary/compressed data which can be interpreted later
with some special tool. that way we can register more data (depends on
if you want to log all kernel msgs or just want to save some state of crash information)

anyway, I've always wondered if it wouldn't be possible (at least for many panics)
to write a complete system crash dump to a swap partition (assuming swap > real_mem)
which would be a big help for some problems too.

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