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Re: A problem with Second Sight
juntunen@hotmail.com writes ...
>
> I have a Second Sight card installed into my IIgs and the other day I went to
> try and use Inwords but it just locked the computer up.
> ....
>
> Also, is it just my imagination or does the Second Sight card seem to make the
> gs more unstable? It seems like I have to reboot my machine more often
> because of something or the other crashing.
> ....
It is not your imagination. As Wayne Stewart and Supertimer have
noted, the SS card's power drain tends to make it glitch-causer. The
following excerpts from your csa2 FAQs may help ...
>>
Csa2 FAQs-on-Ground file: FxxxPOWER.txt
The Csa2 (comp.sys.apple2) usenet newsgroup Frequently Asked Questions
files are compiled by the Ground Apple II site, 1997, 1998.
ftp://ground.isca.uiowa.edu/2/apple2/Faqs
http://ground.isca.uiowa.edu/2/apple2/Faqs
The Csa2 FAQs may be freely distributed.
....
005- Could you please explain how adding thicker wire will decrease
noise on the +5V and +12V lines? I received and installed
my new "Heavy Duty" A2 power supply and get the same results
with my Second Sight board as before-- it still locks up the
computer on boot-up.
Ohm's Law says: E = I x R. The Voltage drop across a resistance
equals the Resistance (in Ohms) multiplied by the Current (in Amps).
The leads coming from most A2 power supplies have a low
resistance-- less than an Ohm-- but, as a user piles on peripherals and
current increases, a wire lead's "low resistance" may suddenly prove to
be too high. For example, suppose the +5V lead coming from a GS power
supply has a total resistance of 0.2 Ohms. If the average current load
on the +5V line is 2 Amps, the voltage drop across the wire is 2 x .2 =
0.4 Volts.
If the PS regulation is set to hold the +5V line at +5 Volts (at
the PS end) then, in the above situation, you are running your GS at 5 -
0.4 = 4.6 Volts. The system may run fine even though your main supply
voltage is a little low.
Then, the user adds a ZipGSx accelerator, a RamFAST interface, a PC
Transporter, and/or a Second Sight board. Now, suppose average current
load on the +5V line goes to 3.5 Amps. Our +5V wire now drops 3.5 x .2 =
0.7 Volts. The system must now run with a main supply Voltage of 5 - 0.7
= 4.3 Volts!
Though the above analysis speaks only of average voltages, it is
easy to see that a system designed to work at 5 Volts will eventually
begin to malfunction due to the voltage drop across a skimpy +5V lead.
In fact, any actual computer system would be likely to experience
crashes long before the average, measured at-motherboard voltage got
down to 4.3 Volts.
A Volt-meter reading at the motherboard PS plug does not show
instantaneous spike voltages. Each time a circuit switches, there is a
change in current drain. Quite a few circuits are switched with each
clock transition; so, the change in current can be substantial at 1 x
and 2 x clock frequency. Other events, like turning ON a disk drive, can
also produce brief up or down shifts in current drain. Either way, you
have brief changes in voltage across the PS lead(s) through which the
current is drawn.
The brief voltage changes are called "spikes" because they are VERY
brief. The larger the current shift and the greater the resistance of
the PS wire, the higher the spike Voltage. Since these spikes are in
series with the circuits connected to the PS and since they are
difficult to eliminate via bypass capacitors, they propagate throughout
the system. They are a kind of "noise".
Even worse, as current draw increases and spike voltage increases,
at-motherboard supply voltage decreases. So, you have a 'double whammy':
the lowered supply voltage reduces "noise immunity" just when you need
it most!
At some point, noise spikes appear which cause latches, memory
IC's, etc. to switch state. If the latch is on a RAMfast, you may get a
disk read error. If a memory chip is affected, data will be corrupted,
program instructions may change, ....; in short, your computer is likely
to malfunction.
All of which, to be sure, is "bad enough"; but, evidently, there's
more. Piles of anecdotal evidence indicates that operating the power
supply under such high-noise conditions drastically curtails its life.
How many csa2 posts complain about GS power supplies that crater "for no
reason" after just a couple months? How many users seem to be on eternal
quests for a solution to PS woes?
Our current GS power supply is the one which came with the computer
when it was purchased in the Fall of 1986. The main difference between
our PS and the piles of blown units is that fattened leads were added
back when we upgraded to an accelerator board.
To 'close the loop': you want THICK, heavy-gauge power supply leads
because they have less resistance. Less resistance means that the
voltage drop or loss across the lead is smaller. Noise is reduced AND
noise immunity is increased. Another effect which usually goes
unmentioned is that voltage regulation also improves because the 'sensed
voltage' is closer to the actual at-motherboard voltage.
Perhaps, now, taking a good look at your new Heavy Duty power
supply, you can see why it has not cured your glitch problems. Very
likely it has heavier leads than your old PS; but, the new leads are not
heavy enough.
The PS leads which carry significant currents are +5V, +12V, and
GND. These are the leads which should be replaced with heavier gauge--
e.g. #14 or #12 gauge-- wires. (You need to replace just one of the two
GND leads.)
-------------------------
006- Fattening my GS's power supply leads greatly reduced system
crashes. Is there any more that can be done to eliminate
glitches?
Yes. There is another weak link in the power delivery 'chain': the
motherboard circuit traces supplying power to Slot boards are fairly
skimpy, especially on ROM-01 boards. A heavy power user, such as a
souped-up Transwarp accelerator board, in Slot 7 can produce significant
noise up and down the entire Slot 'backplane'.
The cure is to remove the motherboard and tack on #18 - #16 gauge
jumper leads. (See Question 007 for details.)
--------------------------
007- Does anyone here remember the Mac SE upgrade kit that included
18-ga wire, a bunch of new caps and other fun stuff, that
increased the computer's amperage and allowed more upgrades,
also fixed many problems? Is there a power supply upgrade kit
for the Apple IIgs that someone has constructed?
Okay; here is your very own
A2-2000 On-Line Power Supply Mods Kit!
Swapping-in fat leads is, technically speaking, a pretty simple
job. You pop out the power supply, open it, unsolder old +5, +12, and
Ground leads, solder in the new leads, close and replace the power
supply. The tricky part is what hackers call the "mechanics".
First, #12 or #14 gauge wire is not very flexible. Getting stranded
wire (instead of solid) helps. Probably, #14 gauge is more than fat
enough for all three leads. One case where #12 or #10 gauge may be worth
the extra trouble is the +5V lead.
Use wires colored the same as those you replace. On the standard
connector, the first two leads are Ground. Almost always, these are
black. Next, there is a space, then, in order +5, +12, -12, -5.
Depending on the bother involved, you can unwedge the wire bundle
where it passes through the supply case and remove the three old wires
(+5V, +12V, and one Ground wire). Or, you can just cut away each old
lead. Leave the -5V and -12V leads and one Ground lead alone.
Getting to the PS circuit board involves some work. After removing
the mounting bolts, you will have to scooch up the board in order to get
to the bottom side. This will be easier if the wire bundle has been
unwedged.
Another hurdle is soldering to the circuit board. Once the old
leads and excess solder are removed, you will probably find that the
holes are too small! A jeweler's screwdriver makes a good hand drill for
enlarging holes. (Drill from the circuit side. Be careful not to tear or
dislodge the printed circuit.)
The new leads should be routed through the unused fan slots. (If a
fan is attached, remove it. It's in the wrong place to do much good in
cooling your GS.)
Note: If you have a fan mounted to the PS and you wish to keep it, then,
it will be necessary to enlarge the original cable exit hole. A sheet
metal "munching" tool should let you do this without having to entirely
remove the PS circuit board. (Just be sure to catch all of the munched
pieces!)
When routing the leads be careful not to place a twisting force on
a lead where it is soldered to the circuit board.
To get to each spronger (contact) in the plug, press on it through
the slot on the side near the wire end. This pushes up a small retaining
tab so that pulling on the attached lead will pull out the spronger.
Cut off the old lead, clean the end, and solder on the new lead.
Press the spronger back into the plug. To avoid mixups, it's best to
complete the process for each lead before doing the next.
When plugging in the power supply, take time to shape and arrange
the wires to minimize stress on the motherboard.
Motherboard Mod
Fatter +5, +12, and Ground leads should protect you power supply
and reduce circuit noise.
If audio noise in your stereo card output and/or system bombing due
to noise glitches were problems, they may be eliminated. A lot depends
upon which cards you've installed, which slots they are in, and whether
your IIgs is a ROM-01 or ROM-03.
The motherboard circuit traces supplying power to each Slot are
fairly skimpy, especially on ROM-01 boards. A heavy power user in Slot 7
can produce significant noise up and down the entire Slot 'backplane'.
The cure is to remove the motherboard and run leads to a couple
Slots ...
First, flip over the motherboard and get oriented. Below is a
quickie sketch showing the Power Connector points as well as key power
pins for a Slot. The view is from the _Bottom_ with the _Back_ of the
motherboard facing you:
Bottom of Motherboard
Power Connector Socket Slot
X GND +12V (pin 50) X X (pin 1)
X GND X X
.
X +5V .
X +12V .
X -12V
X -5V X X
GND (pin 26) X X (pin 25) +5V
.... Ground Plane Area (plug shields, etc. connected here) ....
|
|______________ Back Edge of Motherboard _________________________
A good way to make sure you know what's where is to use an Ohm
meter to check Resistance from pin 26 (GND) to a metal plug shield near
the back of the motherboard. (Set your meter to Ohms X1. Touch one meter
lead to pin 26 and the other to a metal plug shield. Resistance should
read nearly zero. Reverse the leads and repeat the check. Again,
Resistance should read nearly zero.)
Repeat the check for R between pin 26 and the GND points on the
Power Connector socket. R should be nearly zero. Using a marker pen or
white-out, mark pin 26 (GND) on Slots 3 and 7. Also mark the GND points
of the Power Connector socket.
GND: On the bottom side of the motherboard, connect a Black #16 gauge
wire from one of the Ground points of the Power Connector socket to the
Ground plane area near the back of the motherboard. Run a short Black
#16 gauge wire from pin 26 of Slot 3 to the Ground plane; run a short
Black #16 gauge wire from pin 26 of Slot 7 to the Ground plane. (You may
need to scrape through green insulating lacquer to solder to the Ground
plane area.)
+5V: On the bottom side of the motherboard, connect two #16 gauge Red
wires to the +5V point of the Power Connector socket. Connect the other
end of one +5V Red wire to pin 25 of Slot 3; connect the other end of
the second +5V Red wire to pin 25 of Slot 7.
+12V: If you have any cards which are likely to draw heavily on the +12V
line, then, on the bottom side of the motherboard, run a #18 gauge White
wire from the +12V point of the Power Connector socket to pin 50 of the
Slot in which the card is normally located. Otherwise, just run an #18
gauge White wire from the +12V point of the Power Connector socket to
pin 50 of Slot 7.
Check your connections. One quick check is that the GND and +5V
wiring to Slots 3 and 7 should be Black, Red (moving left to right) and
Slots 3 and 7 should 'look the same'. Any +12V wire should be on the
same side of the Slot (i.e. the same column of pins) as GND. None of the
wires should be connected to a middle pin on any Slot.
Notes:
1. All wires are insulated.
2. When cutting wires, allow enough slack to permit routing each wire.
You want to avoid having a wire rest against pointy connections on the
motherboard. Route wires away from motherboard mounting holes and around
places where the bottom of the case supports the motherboard.
3. The case's bottom and back metal shields are something of a shorting
hazard. Replacing the motherboard is much easier if these shields are
popped out and ditched.
Once everything checks out, replace the motherboard taking care
that no wires are caught between a support point and the motherboard.
__________________________
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Rubywand