2 Nov
2010
2 Nov
'10
10:54 p.m.
No one seemed to notice this, but I thought I'd post it for Tony's
edification. It's a story in the October 7 EDN from the "Tales from
the Cube" back section and deals with solving a problem with the I/O
board of the HP9845:
http://bit.ly/cNwokC (it's a PDF)
Enjoy,
Chuck
3 Nov
3 Nov
1:42 p.m.
No one seemed to notice this, but I thought I'd post it for Tony's
edification. It's a story in the October 7 EDN from the "Tales from
the Cube" back section and deals with solving a problem with the I/O
board of the HP9845:
http://bit.ly/cNwokC (it's a PDF)
Interesting... Why specifically for me, though (other than I have an
HP9845B which AFAIK uses the same I/O backplane PCB).
A few comments...
For those who don't know the machine, the I/O backplane fits at the rear,
behind the PSU. It has 4 edge connectors for interface modules which plug
into the rear of the machine. The PCB carries the connecotrs, some bus
buffer chips and not a lot else.
The problems with the origianl design seem to indicate that 'there is no
such thing as groudn' )(with thin tracks, 2 points that both claim to be
'ground' woukld not always be at the same voltage), and that the most
complciated part of a digital circuit is the wire :-)
I am also a little suprised by the comment that logic analysers didn't
really exist at that time (not that a logic analyser would have been a
lot of help fo this fault). I am wondering how the older HP machines
were actually debugged. Having repaired several of them, I find a logic
alauyser to be next-to-essential. Even more so if the design is not known
to be sound.
-tony
2:47 p.m.
On 3 Nov 2010 at 20:42, Tony Duell wrote:
Interesting... Why specifically for me, though (other
than I have an
HP9845B which AFAIK uses the same I/O backplane PCB).
I seemed to recall that you specifically have an interest in the old
HP 9800 series. If you don't care for things such as this, I'll make
a note to ignore them.
I am also a little suprised by the comment that logic
analysers didn't
really exist at that time (not that a logic analyser would have been a
lot of help fo this fault). I am wondering how the older HP machines
were actually debugged. Having repaired several of them, I find a
logic alauyser to be next-to-essential. Even more so if the design is
not known to be sound.
Oscope, in particular storage-tube scopes.
The HP 1600A dates from 1976 and was marginally useful. The 1602A
dates from 1978. I remember getting one to evaluate from Electro-
Rents and thought it very cool, but didn't use it all that much. We
had a logic analyzer plugin for the Tek 7400 series scope frame that
was good enough--and lots cheaper.
--Chuck
4 Nov
4 Nov
1:04 p.m.
On 3 Nov 2010 at 20:42, Tony Duell wrote:
My first word was 'interesting'. I was not being sarcastic, I did find the
article interesting.
I was sort-of wondering if you thougth I was the only person on
classiccmp who likes old HPs (untrue), if you thought I'd miss the
articel while everyone else would have seen it (well, I would have missed
it, whether others would have see it is another matter), or whether you
thought I'd somehow not realise the importance of low-impedance ground
conenctions (believe me, I do...). But anyway...
I see no problem with posing references to articles relating to classic
manchines here.
Interesting... Why specifically for me, though
(other than I have an
HP9845B which AFAIK uses the same I/O backplane PCB).
I seemed to recall that you specifically have an interest in the old
HP 9800 series. If you don't care for things such as this, I'll make
a note to ignore them. I am also a little suprised by the comment that
logic analysers didn't
really exist at that time (not that a logic analyser would have been a
lot of help fo this fault). I am wondering how the older HP machines
were actually debugged. Having repaired several of them, I find a
logic alauyser to be next-to-essential. Even more so if the design is
not known to be sound.
Oscope, in particular storage-tube scopes.
The HP 1600A dates from 1976 and was marginally useful. The 1602A
I rememer seeing an HP 'scope plug-in that IIRC stored soemthing like 16
samples from 16 channels and displayed them in binary on the 'scope
screen. Primitive by today's standards, but I bet it was very useful if
you had nothing lese.
dates from 1978. I remember getting one to evaluate
from Electro-
Rents and thought it very cool, but didn't use it all that much. We
had a logic analyzer plugin for the Tek 7400 series scope frame that
was good enough--and lots cheaper.
I used a Tekky 7D01 logic analyser plug-in at univertisty. It got would
the problem of too-slow RAM by storing successinve samples in different
RAMs at the fastest sample rates. I think you had 4 channels at the
fastest rate, 8 at the next-fastestm, and 16 at all the slower sample
rates.. It was actually quite useable...
-tony
3:04 p.m.
On 4 Nov 2010 at 20:04, Tony Duell wrote:
I was sort-of wondering if you thougth I was the only
person on
classiccmp who likes old HPs (untrue), if you thought I'd miss the
articel while everyone else would have seen it (well, I would have
missed it, whether others would have see it is another matter), or
whether you thought I'd somehow not realise the importance of
low-impedance ground conenctions (believe me, I do...). But anyway...
My take was that it was an anecdote by one of the people associated
with the HP 9845 project. Had it been just a bunch of technical
specifications or sample code, I would have ignored it--and I didn't
think you subscribed to EDN.
But this was a War Story.
I'm more interested in the mind of the developer and and much less in
the actual physical hardware itself. After all, any of the old
hardware could, given sufficient resources, recreated or simulated.
It's the people that's irreplaceable.
--Chuck
I see no problem with posing references to articles relating to
classic manchines here.
I guess they did have sufficient bandwidth...
I am also a little suprised by the comment that
logic analysers
didn't really exist at that time (not that a logic analyser would
have been a lot of help fo this fault). I am wondering how the
older HP machines were actually debugged. Having repaired several
of them, I find a logic alauyser to be next-to-essential. Even
more so if the design is not known to be sound.
Oscope, in particular storage-tube scopes.
The HP 1600A dates from 1976 and was marginally useful. The 1602A
I rememer seeing an HP 'scope plug-in that IIRC stored soemthing like
16 samples from 16 channels and displayed them in binary on the 'scope
screen. Primitive by today's standards, but I bet it was very useful
if you had nothing lese.
dates from 1978. I remember getting one to
evaluate from Electro-
Rents and thought it very cool, but didn't use it all that much. We
had a logic analyzer plugin for the Tek 7400 series scope frame that
was good enough--and lots cheaper.
I used a Tekky 7D01 logic analyser plug-in at univertisty. It got
would the problem of too-slow RAM by storing successinve samples in
different RAMs at the fastest sample rates. I think you had 4 channels
at the fastest rate, 8 at the next-fastestm, and 16 at all the slower
sample rates.. It was actually quite useable...
-tony
5 Nov
5 Nov
3:08 p.m.
My take was that it was an anecdote by one of the
people associated
with the HP 9845 project. Had it been just a bunch of technical
specifications or sample code, I would have ignored it--and I didn't
Actualloy, if you come across anything related to classic computers
(inclduing specs or sample code), I think it should be mentioned here.
think you subscribed to EDN.
I don't. I read it years ago when I had a job. Not any more.
But this was a War Story.
FWIW, I do find war stories interesting...
I'm more interested in the mind of the developer and and much less in
the actual physical hardware itself. After all, any of the old
hardware could, given sufficient resources, recreated or simulated.
It's the people that's irreplaceable.
I have almost the opposite view based on similar reasons/ Alas people
have to die sometime, and they cannot be kept going as long as you like.
Hardware often can be (as you said _anything_ can be recreated given
enough resources). So I am much more interested in keeping the actual
hardware operational.
-tony
5162
days inactive
5164
days old
5 comments
2 participants
participants (2)
-
ard＠p850ug1.demon.co.uk -
cclist＠sydex.com