28 Nov
2007
28 Nov
'07
12:53 p.m.
I'm having a bad day here ..
I mistook an IBM Industrial CGA display for a monochrome display, and
plugged it into a monochrome display adapter port. There was no smoke
or funny noises, but it definitely did not work.
I've heard stories about the IBM monochrome displays being fragile
when mishandled like this. Were the IBM CGA displays also this fragile?
(I won't be able to test it until I dig out a CGA card. And now of
course I'm just paranoid and hoping that I didn't hurt it.)
Mike
28 Nov
28 Nov
3:55 p.m.
mbbrutman-cctalk at brutman.com wrote:
I mistook an IBM Industrial CGA display for a
monochrome display, and
plugged it into a monochrome display adapter port. There was no smoke
or funny noises, but it definitely did not work.
I've heard stories about the IBM monochrome displays being fragile when
mishandled like this. Were the IBM CGA displays also this fragile?
(I won't be able to test it until I dig out a CGA card. And now of
course I'm just paranoid and hoping that I didn't hurt it.)
CGA is 15.75KHz H and 60Hz V; monochrome is 18.4KHz H and 50Hz V.
That's pretty similar bandwidth, and I haven't heard any stories nor
personally experienced that doing what you did would release the magic
smoke. If you didn't hear a loud high-pitched whine, or smell ozone, I
wouldn't worry about it.
I *have* witnessed a monochrome monitor releasing the magic smoke
through software, but the software in question was something that fed
random values to all of the MDA ports in rapid succession. Who knows
what kind of timings (or pulses!) were responsible for blowing it up...
--
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Or check out some trippy MindCandy at http://www.mindcandydvd.com/
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4:08 p.m.
There was an urban myth back in the late 80's and early 90's that there
was a virus going around that could alter the scan rate of a video
adapter so that it would blow out the monitor. Never saw any such
damage to a monitor in person, so I don't know if it was just a myth or
actually existed.
Used to see the little cap in the corner of hercules cards pop and
flicker on fire though, that was always neat.
Nothing beat the Bernoulli boxes, the originals in the XT cases, there
was a design flaw in the power supplies, they had these big honk'n coke
can sized caps on them and they would explode! No kidding, I used to
work at a downtown financial client and this one floor had dozens of
them hooked up to AT's and such and every once in a while you'd hear
this BANG!!! It sounded like someone smacking the XT case ontop with a
hammer. Sure enough you'd open up the case and the underside would
have this black mark were the cap exploded. Bournelli issued
replacement p/s' and the problem went away :-)
Curt
Jim Leonard wrote:
mbbrutman-cctalk at brutman.com wrote:
I mistook an IBM Industrial CGA display for a
monochrome display, and
plugged it into a monochrome display adapter port. There was no
smoke or funny noises, but it definitely did not work.
I've heard stories about the IBM monochrome displays being fragile
when mishandled like this. Were the IBM CGA displays also this fragile?
(I won't be able to test it until I dig out a CGA card. And now of
course I'm just paranoid and hoping that I didn't hurt it.)
CGA is 15.75KHz H and 60Hz V; monochrome is 18.4KHz H and 50Hz V.
That's pretty similar bandwidth, and I haven't heard any stories nor
personally experienced that doing what you did would release the magic
smoke. If you didn't hear a loud high-pitched whine, or smell ozone,
I wouldn't worry about it.
I *have* witnessed a monochrome monitor releasing the magic smoke
through software, but the software in question was something that fed
random values to all of the MDA ports in rapid succession. Who knows
what kind of timings (or pulses!) were responsible for blowing it up... 
4:25 p.m.
In article <474E0308.2010901 at atarimuseum.com>,
"Curt @ Atari Museum" <curt at atarimuseum.com> writes:
There was an urban myth back in the late 80's and
early 90's that there
was a virus going around that could alter the scan rate of a video
adapter so that it would blow out the monitor. Never saw any such
damage to a monitor in person, so I don't know if it was just a myth or
actually existed.
Its not an urban legend. The issue was that there was a sync register
(horizontal sync, I think) for which you could poke in a zero value.
That's what I recall anyway, although I can't dredge up anything by
google at the moment.
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29 Nov
29 Nov
9:25 a.m.
On 29/11/2007, Richard <legalize at xmission.com> wrote:
Its not an urban legend. The issue was that there was
a sync register
(horizontal sync, I think) for which you could poke in a zero value.
That's what I recall anyway, although I can't dredge up anything by
google at the moment.
Surely this is a variant on the legendary HCF operand?
http://en.wikipedia.org/wiki/Halt_and_Catch_Fire
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28 Nov
28 Nov
4:10 p.m.
I'm having a bad day here ..
I mistook an IBM Industrial CGA display for a monochrome display, and
plugged it into a monochrome display adapter port. There was no smoke
or funny noises, but it definitely did not work.
I've heard stories about the IBM monochrome displays being fragile
when mishandled like this. Were the IBM CGA displays also this fragile?
No. Doing the revers (5151 MDA monitor into CGA card) lets the smoke out
of the monitor, but the CGA monitor shouldn't be easily damagrd.
-tony
4:38 p.m.
Tony Duell wrote:
No. Doing the revers (5151 MDA monitor into CGA card)
lets the smoke out
of the monitor, but the CGA monitor shouldn't be easily damagrd.
-tony
Ok, I'm feeling a little better. I'm not touching any more hardware today.
Tomorrow I will install a CGA card into the machine (5160) and try
again. The industrial CGA is quite the looker .. it has a Plexiglass
shield covering the front, it is rather boxy in shape, and it has air
filters covering the intake vents on the bottom. The monitor also has a
fan .. I was quite surprised when I powered it up and heard the fan noise.
Mike
4:14 p.m.
On 28 Nov 2007 at 12:53, mbbrutman-cctalk at brutman.com wrote:
(I won't be able to test it until I dig out a CGA
card. And now of
course I'm just paranoid and hoping that I didn't hurt it.)
Shouldn't bother a CGA, other than not syncing. For that matter, an
MDA plugged into a CGA port, while not giving an in-sync display,
should not emit magic smoke.
It *is* possible to damage an MDA by cranking the horizontal sync up
to the point where it's *almost* too high for the display to
maintain sync; i.e., you're running the MDA on the "bleeding high
limit" of horizontal sync. The casualty is usually the HOT.
But that's not what's going on here.
Cheers,
Chuck
29 Nov
29 Nov
12:55 p.m.
On 28 Nov 2007 at 12:53, mbbrutman-cctalk at brutman.com wrote:
The design of the horizontal drive stages is very different between the
MDA nad CGA monitors.
The CGA monitor is conventional, in that there's the normal
horizontal oscillaotr/PLL circuit. I doubt that it would run far enough
off-frequency to damage the output stage no matter what frequency of sync
pulse you gave it (althoguh it will obviously not lock).
The MDA monitor is simple. There is no horizontal oscillator circuit _at
all_. The incoming sync pulses (or rather, drive pulses) go to the base
of the horizontal drive transistor, which is transformer-coupled to the
output transistor. It's possible to drive that way off frequncy, where
the output stange is no longer resonant, and then the output transistor
(HOT to you) fails.
I suspect (although I am not trying it), that you could damage an MDA
monitor by plugging it into a CGA card.
Note that this applies to the IBM monitors. Some clone MDA monitors had
the conventional oscillator/PLL circuit, I assume they're a lot harder to
damage.
With regards to the 'killer poke' somebofy mentioned, It's impossible to
bring the drive frequency down to 0, the signal is capcitor and
transofrmer coupled. But it's certainly possible to reprogram the 6845 on
the MDA board to drive the monitor way off-frequency, at which point the
HOT is likely to fail.
-tony
(I won't be able to test it until I dig out a
CGA card. And now of
course I'm just paranoid and hoping that I didn't hurt it.)
Shouldn't bother a CGA, other than not syncing. For that matter, an
MDA plugged into a CGA port, while not giving an in-sync display,
should not emit magic smoke. 
3:26 p.m.
With regards to the 'killer poke' somebofy
mentioned, it's impossible
to bring the drive frequency down to 0, the signal is capcitor and
transofrmer coupled.
Well, I suppose this depends on whether you consider the absence of a
signal to be a frequency of 0. :-)
But it's certainly possible to reprogram the 6845
on the MDA board to
drive the monitor way off-frequency, at which point the HOT is likely
to fail.
Sticking a 0 in the register doesn't necessarily mean setting the
frequency to 0; I would expect that the register is, loosely, the
reciprocal of the frequency (much the way BRGs in UARTs often require
the baud rate to be set by specifying a value by which some clock is
divided to get the baud clock). Setting it to zero would likely give
you as high a frequency as the electronics can generate, under which
circumstances it's no surprise the magic smoke gets let out given what
you said about the horizontal stage of the MDA monitor.
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30 Nov
30 Nov
5:35 p.m.
All is well - the industrial CGA display is happy being connected to a
real CGA card. It's quite the looker too. People at the office are
impressed, possibly not in a good way. ;-0
The machine (a 5160) has the monochrome adapter (Hercules), a genuine
CGA card, a 3Com 3C503, memory, serial, floppy and a hard disk
controller. It has 512KB of RAM and a full height 10MB hard disk.
NCSA Telnet *was* running on before I put the CGA card in. (I had a
Cirrus Logic VGA card in it yesterday.) Now NCSA Telnet is hanging on
startup after reading it's config file. I'm having a hard time
believing that the CGA card replacing the VGA card broke it, so I'm
going to have to undo my changes and try again. My own TCP/IP still
works, so I know it's not a hardware conflict. (It's pretty hard to get
CGA to conflict with anything.)
Mike
6:57 p.m.
New subject: Shugart 801 drives?
There are two of these for sale in unknown condition. They are big old
8" drives. I've never owned an 8" drive before, and I'm thinking that
it would be neat to interface them to an older PC.
Any words of advice? Are they difficult to work with or interface?
(Any more difficult than an older 5.25" drive?)
Mike
9:51 p.m.
New subject: Shugart 801 drives?
Michael B. Brutman wrote:
There are two of these for sale in unknown condition. They are big
old 8" drives. I've never owned an 8" drive before, and I'm thinking
that it would be neat to interface them to an older PC.
Any words of advice? Are they difficult to work with or interface?
(Any more difficult than an older 5.25" drive?)
Mike
main thing to watch out for is that they take 5, 12 and 28 (i think)
volt ps which has to be pretty substantial. If they come w/o that take
care what you hook them up with.
There probably are a lot of threads on this forum about 8" to PC's w/o
opening that can of worms before you search that source of information.
Jim
11:33 p.m.
New subject: Shugart 801 drives?
On 30 Nov 2007 at 21:51, jim s wrote:
main thing to watch out for is that they take 5, 12
and 28 (i think)
volt ps which has to be pretty substantial. If they come w/o that take
care what you hook them up with.
+5, +24, -5 volts, no +12. As long as you have a capable (i.e. if
you're going to be handling FM, your controller has to support FM.
If you're putting this on a PC XT, you have to have a controller
capable of 500K data rate) controller on your PC, you're fine.
If you're going to be using the drive in 801 (i.e. hard sectored)
mode, that's a whole 'nother topic and usually involves a Catweasel
or some such board on a PC.
Wiring a cable is pretty straightforward and involves matching 8"
drive signals up with like 5.25" signals on the controller. I
normally wire HEAD LOAD to the corresponding MOTOR ON line on the PC,
but I've heard of some wiring it to SELECT and SELECT to MOTOR ON.
Your choice.
Cheers,
Chuck
9:58 p.m.
New subject: Shugart 801 drives?
At 08:57 PM 11/30/2007 -0600, you wrote:
There are two of these for sale in unknown condition.
They are big old 8"
drives. I've never owned an 8" drive before, and I'm thinking that it
would be neat to interface them to an older PC.
Any words of advice? Are they difficult to work with or interface? (Any
more difficult than an older 5.25" drive?)
I have a Shugart 801 for sale with power supply (no case), Price: reasonable.
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12:01 p.m.
Michael B. Brutman wrote:
NCSA Telnet *was* running on before I put the CGA card in. (I had a
Cirrus Logic VGA card in it yesterday.) Now NCSA Telnet is hanging on
startup after reading it's config file.
Check the config file; there is a video mode line IIRC.
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
12:40 p.m.
Jim Leonard wrote:
Michael B. Brutman wrote:
Been there ..
Other people have reported weirdness with NCSA Telnet on an XT before.
If I put the VGA card back in and it works, I'll have it narrowed down.
NCSA Telnet *was* running on before I put the CGA card in. (I had a
Cirrus Logic VGA card in it yesterday.) Now NCSA Telnet is hanging on
startup after reading it's config file.
Check the config file; there is a video mode line IIRC. 
1:55 p.m.
Quoting "Michael B. Brutman" <mbbrutman-cctalk at brutman.com>:
Jim Leonard wrote:
For what it's worth. I've lately been successfully running NCSA Telnet on a
'XT-ized' Tandy 1000A. It's got 640KB and 20MB MFM. Also, the T1000 has that
weird blend of CGA and 16-color CGA that was in the PCjr (don't remember what
it's acronym is, right now), but I have no problems running the NCSA Telnet
package. My config is set for 'CGA'.
- Jared
Michael B. Brutman wrote:
Been there ..
Other people have reported weirdness with NCSA Telnet on an XT before.
If I put the VGA card back in and it works, I'll have it narrowed
down.
NCSA Telnet *was* running on before I put the CGA card in. (I had a
Cirrus Logic VGA card in it yesterday.) Now NCSA Telnet is hanging
on startup after reading it's config file.
Check the config file; there is a
video mode line IIRC.
2:25 p.m.
Michael B. Brutman wrote:
Been there ..
Other people have reported weirdness with NCSA Telnet on an XT before.
If I put the VGA card back in and it works, I'll have it narrowed down.
But that wouldn't make any sense since it works for my 8088w/CGA and the
two cards don't conflict...
The only lines in my config file I can think of that may relate are:
(config.tel:)
video=cga # type of video screen
# Legal values for video are:
# cga,ega,pga,no9,hercules,ega43,vga50
# Default is ega
bios=no # don't use slow BIOS screen access
# bios=yes to reduce flicker on cga
# bios=yes for TopView or Windows
# Default is no
Couldn't hurt to turn on "consoledebug=1" too...
--
Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/
Help our electronic games project: http://www.mobygames.com/
Or check out some trippy MindCandy at http://www.mindcandydvd.com/
A child borne of the home computer wars: http://trixter.wordpress.com/
NCSA Telnet *was* running on before I put the CGA card
in. (I had a
Cirrus Logic VGA card in it yesterday.) Now NCSA Telnet is hanging
on startup after reading it's config file.
Check the config file; there is a video mode line IIRC.
6231
days inactive
6234
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18 comments
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