From mboxrd@z Thu Jan 1 00:00:00 1970 Mime-Version: 1.0 (Apple Message framework v752.3) In-Reply-To: <20080528000641.GA2649@skaro.cthulhu.dircon.co.uk> References: <13426df10805271502s7e78ba0dw826dd2f6d982304c@mail.gmail.com> <20080528000641.GA2649@skaro.cthulhu.dircon.co.uk> Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Message-Id: Content-Transfer-Encoding: 7bit From: Paul Lalonde Date: Tue, 27 May 2008 19:54:29 -0700 To: Digby Tarvin , Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net> Subject: Re: [9fans] A shot in the dark Topicbox-Message-UUID: ade092b2-ead3-11e9-9d60-3106f5b1d025 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 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 > -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.3 (Darwin) iD8DBQFIPMllpJeHo/Fbu1wRAtBGAJ49Ngab2WyOW+bYQ0wiUmJrqBKyeACfYhhn A9b4diGkwg2fiiLyjXVWIGY= =3r1V -----END PGP SIGNATURE-----