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FWIW, we used a similar technique just last summer debugging some PS3
code. The dev system is kind enough to include 4 front panel lights
and a very lightweight API for setting them. We wound up "printing"
out the program counter during a deadlock by mashing too many calls
to set the lights into the suspect areas.
I miss hardware debuggers.
Paul
On May 27, 2008, at 5:06 PM, Digby Tarvin wrote:
Don't know where to find that paper, but it reminds of a friend
at UNSW (in Sydney) that used to instrument the OS9 kernel by setting
and clearing bits in the parallel port.
The monitoring hardware was indeed simple - an analogue voltmeter
connected to the bit of interest to produce a simple but effective
short term average.
For example, a bit that is cleared when in the system idle loop
produced a 'tacho' style analogue load meter.
That must have been in the early 80's, but I still find the parallel
interface a good method of getting real-time diagnostics, or front
panel style indicators for statuses such as system/user mode.
Consequently I don't welcome the current trend toward optimising
them out of new hardware. USB parallel interfaces may be ok for
driving printers, but they are no substitute if you want a very low
overhead, low latency i/o mechanism.
Regards,
DigbyT
On Tue, May 27, 2008 at 06:54:58PM -0400, Pietro Gagliardi wrote:
No, I wasn't around that time :-) But I was looking for the Hello
World X11 paper a while back, which was pre-website USENIX. But on
the
USENIX website it seems that you can purchase papers from before
1991(?). Perhaps they had a paper?
On May 27, 2008, at 6:02 PM, ron minnich wrote:
OK, this is a long shot, but i'm running out of ideas.
Long, long ago, at a Usenix, I saw a talk by some adventurous
australians (are there any other kind?). It was concerning some neat
hardware designed for kernel monitoring.
They had done a very neat hack. Basically, they modified the C
compiler so that, on function entry and exit, the code would emit a
16-bit quantity to the parallel port. They had some simple
hardware to
grab the data.
WIth this, they were able to get some nice kernel performance
numbers,
all for the (low at the time) cost of an outw to the parallel port.
OK, I have done some searching and can't find this. IIRC it was
pre-website usenix. I am going to UCB this week and may have time to
hunt it down in the paper archives, but ... just wondering ...
anyone
else remember this?
thanks
ron
--
Digby R. S. Tarvin digbyt
(at)digbyt.com
http://www.digbyt.com
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