5 Oct
2007
5 Oct
'07
5:24 p.m.
On 05/10/2007, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
OK, a higher-level description would be 'something that records a number
of digitla signals and displays their relative timing'.
The sorts of things you might use one for would be to trace machine code
(or microcode!) instructions/addresses on a processor bus (but cache
memory and even a pre-fetch buffer makes that a little hard!), checking
things like handshake sequencies on an interface, recording bit-seiral
signals so you can decode them later, checking state machine sequences,
and so on.
[Nod]
But as I said elsewhere, for my clients today, if a machine is less
than a couple of gigahertz, it's skipware. It's not worth my time to
try to diagnose a fault; if it fails, swap it out and replace it with
a new machine.
It's taken me a long time to accept this, but it is the most sensible
method; my job is to economically deliver a working, stable system for
my clients, not to nurse their old kit along as long as possible.
For my own kit, the rule is similar, /pace/ that I am unwilling to
spend any money at all on it if at all possible. Things get replaced
once there's a better replacement waiting for free.
A logic analyser is a bit lile a 'scope in that it
displays a grpah of
signals against time. The differnces are (a) it records the signals and
displays the recorded version (some 'scopes do that too -- storage
'scopes), (b) it only works with digital signals (it doesn't display th=
e
voltage, only whether they are high or low), and
(c) it has many more
input channels (even a good 'scope rarely has more than 4 channels, a
logic analyser will have 16 or more).
Fascinating. The snag is, I know very little about electronics below
the level of a broad knowledge of TTL, the rudiments of circuits and You mean oyu've not been on the receiving end of
my flames about this
:-). Suffice it to say I've just written a presentation where I describe
that as a 'ridiculous method'.
I take your point, but what I'm talking about here is swapping DIMMs
and video cards and so on in PCs. A PC more than about 3-4yr old is
not worth fixing; extract the data, maybe cannibalise some bits, and
bin in. (Which actually means, ship it off to ComputerAid.)
Nonetheless, PCs depreciate in about 3yr. After that, you don't fix,
you replace.
Macs are much the same but it's maybe 4-5y if they're not in demanding
roles. However, the vastly superior build quality usually means that
they last until they're too old and slow to be any use to anyone.
I actually wonder how you can be 'competent with
hardware' and 'know
bugger-all about electronics' To me those are contradictory statements.
I realize that. But I did specify earlier: I don't generally work
below the level of the circuit board. There's no single part of a PC
bar the CPU that's generally worth more than ?50, and I charge ?75 an
hour. If it's duff, stick in a new one.
We also ssem to have different attidudes about
learning new things. I
tend to spend the time to learn whatever I need to fix the problem. I
don't claim to be a programmer, I;d never write an OS or a compiler or an
emulator, or.. from scratch. But when I had a problem which was clearly
due to a device driver not correctly hadnling the somewhat odd hardwre
in my PC, I learnt enough C to understand how said driver worked, and
then editied the sources to get it to work.
Well, maybe you learn stuff like that easier than I do!
Actually, there are some ISA boards I am still looking
for. Top of the
list is an origianl IB< PGC.
I don't know what that is. I have a bag of ISA kit: mostly multi-I/O
cards, sound cards, some NICs, and a few bits of relative exotica like
a Hayes Enhanced Serial Port & a Colorgrafix dual-head ISA VGA card.
If anyone here wants them, they can have them!
I don't suppose your Apple bits include
Laserwriter spares, do they? I am
looking for partially-dead boards to raid for custom chips (PALs,
microcontrollers, etc)
I have a dead Mac IIsi & a dead LC475, from memory. If you want them
to cannibalize, you're very welcome to them. I can probably even
deliver. I think I also have a flakey Umax PPC604 clone machine and a
flakey Beige G3/300 minitower. Likewise, if you want them, you can
have them. Might prove interesting projects to get working again? One
would make a decent MacOS 9 system, the other a slow but workable
low-end Mac OS X box, ideally with 10.3, I suspect. I would be happy
to help and can provide media and so on for these OSs too.
--
Liam Proven ? Profile: http://www.linkedin.com/in/liamproven
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