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A: This
is a problem with some computer systems. The message is the result of an
Interrupt Overrun, as described below.
Symptom: At low frequencies, generally less than 0.1 Hz, an Error Message is
displayed containing the warning "Stuck in a Reading
Loop." The status line at the bottom of the runner window contains the
message "Interrupt Overrun."
Cause:
An interrupt is a signal generated by a hardware device such as a Gamry
potentiostat which tells the computer that the device requires attention.
Gamry potentiostats generate interrupts whenever a data point has been
acquired. In particular, the
EIS300 software generates data and interrupts the computer every 1.2 ms.
If the computer cannot read that data from the potentiostat before
the next data point is taken, an "Interrupt Overrun" error occurs.
A
computer’s responsiveness to interrupts is known as "Interrupt
Latency". Normally
the interrupt latency of a modern Pentium II is on the order of 50-200 us,
i.e., when a hardware interrupt occurs, it is serviced within 200 us. However, old software, especially system software known as "device
drivers", can increase interrupt latency by disabling the normal
interrupt response for a long time. When
the EIS300 suffers from Interrupt Overrun errors some bad actor is disabling
interrupts for more than 1.2 ms, or 6 times longer than normal.
It
is also possible that other software can increase interrupt latency. Other software, especially programs created by Microsoft, may give
the computer high-priority (e.g. non-interruptible) tasks to accomplish.
Solution:
First the good news. Version 3.2 of the EIS300 and Gamry Framework is much less sensitive to interrupt
overruns. Basically, it allows
several overruns to occur before terminating an experiment instead of just
one interrupt as in previous versions. Version 4 is even more improved
in this regard. If, however,
you don't wish to upgrade, perhaps you enjoy AVC (aggravation via computer),
then here are
some things to try.
Step
1: Diagnose the overrun
problem.
To
help diagnose overrun problems, we’ve created a special script called
OVERRUN_TEST.EXP. This script
runs a curve similar to the calibration curves but it only reports points
where an interrupt overrun occurs.
Start
OVERRUN_TEST and use an interrupt time of 0.001 sec. Let it run for 24 hours. You shouldn’t see any data points in the
runner window. There should not even be a curve frame drawn since that is
only drawn when the first point is taken. If you have points and a curve, you’ve had interrupt
overruns. Go on to step two.
If
you don’t have interrupt overruns using OVERRUN_TEST at 0.001 sec timing
but you still have problems running the EIS300, especially at low
frequencies, call Gamry.
Step
2: Remove background utilities.
Often
there are background utilities that are running while EIS300 is running.
Use
Ctrl-Alt-Delete to bring up a task list. OSA.EXE and FINDFAST.EXE often interfere with interrupts.
These are installed as part of the Microsoft Office Standard
Installation and automatically start when Windows finishes loading. OSA.EXE is responsible for loading the Microsoft Office shortcut
bar and helping various Microsoft applications load and initialize faster.
FINDFAST.EXE is a notoriously unstable program that indexes
your office files on your fixed drives for full-text content searching.
You
should remove FINDFAST.EXE and OSA.EXE from your Start Up folder. While you’re there, remove the Microsoft Office shortcut as well.
After all, that silly bar just gets in the way most of the time.
Look
in your Start Up folder at C:\Windows\Start Menu\Programs\StartUp. Remove
any links to these utilities you see in there and reboot your computer.
Run the OVERRUN_TEST again as described in Step 1.
Still
having Overruns? Weed out the
other automatic startup utilities. They
are located in \windows\start menu\programs\startup. You can move these icons to another directory.
Just as an aside, we’ve noticed that changing the name of the
startup folder doesn’t work. Windows
seems to find it even if it is renamed. Perversely clever, isn’t it?
Also
remove or remark out utilities loaded from the AUTOEXEC.BAT and CONFIG.SYS
files. Use the SYSEDIT
utility to get to AUTOEXEC.BAT and CONFIG.SYS. Where’s SYSEDIT ?
From the Start menu pick Run..., and type SYSEDIT in the open
field, then pick OK. A multi-window
Notepad like utility runs. One
window contains CONFIG.SYS and another has AUTOEXEC.BAT.
Reboot
and check the task list again. It
should be much cleaner. Rerun OVERRUN_TEST.
If
you are still having problems, there are other places Windows can
automatically load various utility programs.
Again
using SYSEDIT, look in the WIN.INI file’s [windows] section for lines
like: run=... and load=... . Remove these by putting a semicolon (;) at the beginning of the
line..
Once
you’ve removed everything you can in the utility section, reboot your
computer and try running the OVERRUN_TEST again. If the interrupt overruns at 1 ms have disappeared, try running
EISPOT for an extended time. If EISPOT now runs you can start adding back utility
programs, rebooting, and running OVERRUN_TEST until you find the bad
actor. As we mentioned
before, it is often an annoying Microsoft utility - maybe the one that
animates the nauseating paper clip
or some such thing. Kill it! Don’t let it load. Do without!
If,
when all the excess shrubbery is gone you still have an overrun problem,
go to Step 3.
Step
3: Updating your device
drivers.
Older
device drivers may cause interrupt problems. It is possible to use Window’s Safe Mode to install a plain
vanilla group of device drivers.
To
run in Safe Mode, reboot your computer and hold down the F8 key while it
is booting - starting after the first BEEP. You will see a list of operating modes.
Pick the Safe Mode and allow Windows to continue booting.
Rerun OVERRUN_TEST. At this
point, all should run correctly. If
not, you may have a faulty computer or an older computer which does not
have enough horsepower to run EIS300. We recommend at least a 200 MHz
Pentium to run EIS300 without any other extra tasks. By the way, Windows 98 stripped down this way should run
OVERRUN_TEST easily at 0.001 sec.
If
OVERRUN_TEST runs OK now, you should go through the list of device drivers
and get the latest versions from the manufacturers or from Microsoft.
These are often available on the Web. You should look for drivers that are WHQL (Windows Hardware Quality
Lab) certified. If these are
unavailable for an older device, a video card, for example try using
Microsoft’s standard VGA driver from the Standard Display Types
pick-list during the device driver selection process or replace the device
with a more current model which has WHQL drivers.
Look
for the latest drivers for A) Video Cards, B) Hard Drive Controller, C)
Bus Master, D) Ethernet NIC.
There
is a utility program in Win98 called SYSINFO.EXE that can give you a list
of the current driver set. See
if there are any other drivers that are out of date.
Step 4: Some other things to try
1) Power Management.
Turn
off all the Power Management features so that all portions of your
computer stay powered up at all times. Re-boot your computer and enter the BIOS setup program (observe
monitor during power-up to determine Hot Key). Go to the Power Management Section and disable all power management
features so that all peripherals stay ON while the computer is ON.
2) Turn off display hardware acceleration.
From the Control Panel select Display -> Settings -> Advanced
Properties -> Performance. Set the Hardware Acceleration slider to
"None".
3)
Disable the Screen Saver, as they can tie the processor up needlessly.
4)
Disable any Anti-Virus applications that may be active. If this works, try adjusting the application’s settings to
allow for manual scanning only.
5)
Network Interface Cards and their supporting drivers may also play
a part in inducing interrupt overruns. You should remove the NIC driver
completely to see if it is causing the problem. Heterogeneous networks
with more than two protocol stacks are notoriously balky. Also try getting
the latest NIC drivers from your vendor.
6)
Some peripherals such as removable storage devices that use
parallel, serial, or floppy controller interfaces or PCMCIA adapters to
interface with digital imaging devices may also cause latency problems.
You should stick with the computer’s embedded IDE controller for
such devices.
Step 5: Give up!
Once you’ve installed the latest device drivers and have
eliminated any background utilities and you still have a problem -- you
can call Gamry so we can try to figure out the problem. If it is a
machine not purchased from Gamry, there will be a repair charge.
You must send the computer to us with all of its hardware.
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