Hardware

Pop Quiz Solution: Why pressing [Alt][Tab] locks up the computer

TechRepublic members came up with a number of possible explanations and fixes for this pop quiz challenge. We awarded a Fatbrain.com gift certificate worth $25 to one lucky member.


This week’s pop quiz topic was submitted by TechRepublic member AlHedstrom. If you’d like to suggest a topic for a future pop quiz, please send us a note.

The situation:
Here’s the situation Al described: “While working on a Windows 95 workstation, the user experiences numerous lockups during the normal course of business, all of them occurring when the user employs [Alt][Tab] to switch between DOS apps and Windows apps.”

The facts:
Al provided plenty of details about this behavior: “The system is a Compaq computer P166 with 32 MB RAM, 2-GB hard drive, connected via a 3Com NIC and appropriate client to Novell 5.1 servers and networked printer. The user typically runs MS Word 97, Excel 97, Outlook 98, and two DOS applications. Power-saving options in both BIOS and Win95 Control Panel have been disabled. All updates/service packs have been installed. The usual suspects of memory-hungry apps, need for defrag, various loose connections, flaky keyboard, portable heater under the desk, and irritated user kicking the machine (located under the desk) have all been eliminated. This same configuration on identical hardware runs without problems on other workstations.

“This computer box has been changed twice before, installing to the hard drives in each box the same configuration from both network ’drop-in clone‘ and build-from-scratch methods. We're on the third box, six weeks into this problem, and running out of ideas!

“We currently think that something outside the box is affecting its operation. While the user is pregnant, a doctor client has assured us that this has no effect on machinery or electronics; co-workers, of course, are subject to a variety of pregnancy-induced environmental phenomenon. Any help would be appreciated.”

The challenge:
How do you explain this behavior, and how can Al resolve it?

The solutions
This quiz is one for which there’s no obviously correct solution. So we decided to present some of the solutions we hope can help if you encounter this kind of problem in your shop.

Swap the keyboard?
FritzO. said: “The way I see it, if you change the entire central unit twice and have the same problem, there is nothing wrong with the hardware. The fact that other identical workstations run fine suggests that the hardware/software combination should work. The article mentions that the box has been changed twice, but it does not specifically say that the keyboard was changed. Perhaps the keyboard has a hardware problem, linked to [Alt] or [Tab]?”

Check CONFIG.SYS
WayneC. wrote: “I had a similar situation happen to me when I would [Alt][Tab] between DOS and Windows applications. Solution: Check files= in the CONFIG.SYS file. I had two files= values in the CONFIG.SYS (Ex. files=100 and then files=30). If this doesn't work, swap out the memory in the machine that is giving you problems with memory from another PC. Try it and see.”

It’s the cable, guy
DavidMiller offered this possibility: “Isolate the network drop and patch cables. Switching from an ‘emulated’ DOS NetWare client session back to the Windows environment appears to prompt the NetWare client to recheck its connections to mapped network resources. If there is a serious impediment to network traffic from this workstation, it could cause the NetWare client to ‘freeze’ all other running processes while it waits for confirmation that the network resources are available.”

Order new memory chips
Here’s an opinion from NgotheDuong: “It sounds that the problem occurs when the user changes from low-level memory to high-level memory usage, and vice versa. I guess the machine may have problem with memory. Sometimes some chips in the memory go bad but the system doesn’t report them as bad memory. Change the memory may solve the problem.”

Reload the BIOS?
AllenPowell shared this experience from his shop: “We experienced a similar problem with a few Gateway PCs. We actually stumbled across this by accident. One of my users told me his computer would just ‘reboot for no apparent reason.’ I could not find anything wrong. A few days later, the user called again and had figured out what was happening. For whatever reason, his fingers/hands were combining an [Alt][Spacebar] together and the machine would just reboot. Some of our machines experienced the same problem, but others didn't, and all appeared to be very similar. As a stab in the dark, I loaded/reloaded the latest BIOS on this machine, and the problems disappeared.”

S. E. Rabinowitz agreed: “I know this sounds a little far out—it could be a conflict in the BIOS with the network card. I know the specs say that identical machines do not exhibit the problem, but there may be a version difference in the BIOS. I've seen the same network card work in one machine and cause problems in a supposedly identical machine.”

This week’s pop quiz topic was submitted by TechRepublic member AlHedstrom. If you’d like to suggest a topic for a future pop quiz, please send us a note.

The situation:
Here’s the situation Al described: “While working on a Windows 95 workstation, the user experiences numerous lockups during the normal course of business, all of them occurring when the user employs [Alt][Tab] to switch between DOS apps and Windows apps.”

The facts:
Al provided plenty of details about this behavior: “The system is a Compaq computer P166 with 32 MB RAM, 2-GB hard drive, connected via a 3Com NIC and appropriate client to Novell 5.1 servers and networked printer. The user typically runs MS Word 97, Excel 97, Outlook 98, and two DOS applications. Power-saving options in both BIOS and Win95 Control Panel have been disabled. All updates/service packs have been installed. The usual suspects of memory-hungry apps, need for defrag, various loose connections, flaky keyboard, portable heater under the desk, and irritated user kicking the machine (located under the desk) have all been eliminated. This same configuration on identical hardware runs without problems on other workstations.

“This computer box has been changed twice before, installing to the hard drives in each box the same configuration from both network ’drop-in clone‘ and build-from-scratch methods. We're on the third box, six weeks into this problem, and running out of ideas!

“We currently think that something outside the box is affecting its operation. While the user is pregnant, a doctor client has assured us that this has no effect on machinery or electronics; co-workers, of course, are subject to a variety of pregnancy-induced environmental phenomenon. Any help would be appreciated.”

The challenge:
How do you explain this behavior, and how can Al resolve it?

The solutions
This quiz is one for which there’s no obviously correct solution. So we decided to present some of the solutions we hope can help if you encounter this kind of problem in your shop.

Swap the keyboard?
FritzO. said: “The way I see it, if you change the entire central unit twice and have the same problem, there is nothing wrong with the hardware. The fact that other identical workstations run fine suggests that the hardware/software combination should work. The article mentions that the box has been changed twice, but it does not specifically say that the keyboard was changed. Perhaps the keyboard has a hardware problem, linked to [Alt] or [Tab]?”

Check CONFIG.SYS
WayneC. wrote: “I had a similar situation happen to me when I would [Alt][Tab] between DOS and Windows applications. Solution: Check files= in the CONFIG.SYS file. I had two files= values in the CONFIG.SYS (Ex. files=100 and then files=30). If this doesn't work, swap out the memory in the machine that is giving you problems with memory from another PC. Try it and see.”

It’s the cable, guy
DavidMiller offered this possibility: “Isolate the network drop and patch cables. Switching from an ‘emulated’ DOS NetWare client session back to the Windows environment appears to prompt the NetWare client to recheck its connections to mapped network resources. If there is a serious impediment to network traffic from this workstation, it could cause the NetWare client to ‘freeze’ all other running processes while it waits for confirmation that the network resources are available.”

Order new memory chips
Here’s an opinion from NgotheDuong: “It sounds that the problem occurs when the user changes from low-level memory to high-level memory usage, and vice versa. I guess the machine may have problem with memory. Sometimes some chips in the memory go bad but the system doesn’t report them as bad memory. Change the memory may solve the problem.”

Reload the BIOS?
AllenPowell shared this experience from his shop: “We experienced a similar problem with a few Gateway PCs. We actually stumbled across this by accident. One of my users told me his computer would just ‘reboot for no apparent reason.’ I could not find anything wrong. A few days later, the user called again and had figured out what was happening. For whatever reason, his fingers/hands were combining an [Alt][Spacebar] together and the machine would just reboot. Some of our machines experienced the same problem, but others didn't, and all appeared to be very similar. As a stab in the dark, I loaded/reloaded the latest BIOS on this machine, and the problems disappeared.”

S. E. Rabinowitz agreed: “I know this sounds a little far out—it could be a conflict in the BIOS with the network card. I know the specs say that identical machines do not exhibit the problem, but there may be a version difference in the BIOS. I've seen the same network card work in one machine and cause problems in a supposedly identical machine.”

Power sneaking to the casing?
According to FrancisL., the problem could be electrical. “Improper setup of the hardware (the motherboard is screwed to the casing) can cause some electrical flow to the metal of the casing. Solution: Take out the motherboard with all peripherals, including NIC and other nitty-gritty stuff. Leave the hard drive and floppy and AGP/VGA card—just the basics. And get the Windows to start. Try that [Alt][Tab] a couple of times, adding other hardware components and testing them out until you find the culprit.”

Blame the video card, the network interface card, or the fan
DanR. wrote: “You should try disabling the current video card (not just the driver) by replacing the present video adapter. Use an industry standard such as ATI or Matrox without any 3D or other enhanced video abilities. Install the driver for the new adapter card and see if you still have the problem. You may want to start out with the Windows Safe Mode driver resolution: 640-480 and 16 colors, to verify you have no problems with this situation occurring here first, before you set for the standard display settings.”

CalebL. suggested: “Two things to check: First, try a different NIC. It is possible that the 3Com Windows drivers are having problems. Second, and more likely, verify that the fan(s) are all working properly on the CPU and that you do not have a heat problem. Even if the fan(s) are okay, you should still check and make sure that there is proper airflow to the unit. If this doesn't fix it, I would say you have either a bad RAM chip or at worst a bad motherboard.”

Dirty power lines
Several readers blamed the electrical supply, including KimberlyC., who wrote: “After reading about all the hardware and software troubleshooting that has been done, the two replacement machines, and all that, I would definitely look into the power at that station. I have run into problems where the user was losing data at a phenomenal rate, had several controller cards replaced, a hard drive replaced, and had the entire computer rebuilt, and was still having problems with corrupted data. After sitting down at her desk in her home, and noticing the light flicker when the air conditioner came on, I strongly urged the user to invest in a UPS [uninterruptible power supply], and she has not has a problem like that since then. I would most definitely recommend putting a UPS at that station, and seeing whether that makes a difference.”
Every person who submitted an answer was eligible for the drawing for a $25 gift certificate to Fatbrain. Congratulations to our winner, Ngo the Duong. If you’d like to respond to these suggestions, please post a comment below. If you’d like to suggest a topic for a future quiz, please send us a note.
Power sneaking to the casing?
According to FrancisL., the problem could be electrical. “Improper setup of the hardware (the motherboard is screwed to the casing) can cause some electrical flow to the metal of the casing. Solution: Take out the motherboard with all peripherals, including NIC and other nitty-gritty stuff. Leave the hard drive and floppy and AGP/VGA card—just the basics. And get the Windows to start. Try that [Alt][Tab] a couple of times, adding other hardware components and testing them out until you find the culprit.”

Blame the video card, the network interface card, or the fan
DanR. wrote: “You should try disabling the current video card (not just the driver) by replacing the present video adapter. Use an industry standard such as ATI or Matrox without any 3D or other enhanced video abilities. Install the driver for the new adapter card and see if you still have the problem. You may want to start out with the Windows Safe Mode driver resolution: 640-480 and 16 colors, to verify you have no problems with this situation occurring here first, before you set for the standard display settings.”

CalebL. suggested: “Two things to check: First, try a different NIC. It is possible that the 3Com Windows drivers are having problems. Second, and more likely, verify that the fan(s) are all working properly on the CPU and that you do not have a heat problem. Even if the fan(s) are okay, you should still check and make sure that there is proper airflow to the unit. If this doesn't fix it, I would say you have either a bad RAM chip or at worst a bad motherboard.”

Dirty power lines
Several readers blamed the electrical supply, including KimberlyC., who wrote: “After reading about all the hardware and software troubleshooting that has been done, the two replacement machines, and all that, I would definitely look into the power at that station. I have run into problems where the user was losing data at a phenomenal rate, had several controller cards replaced, a hard drive replaced, and had the entire computer rebuilt, and was still having problems with corrupted data. After sitting down at her desk in her home, and noticing the light flicker when the air conditioner came on, I strongly urged the user to invest in a UPS [uninterruptible power supply], and she has not has a problem like that since then. I would most definitely recommend putting a UPS at that station, and seeing whether that makes a difference.”
Every person who submitted an answer was eligible for the drawing for a $25 gift certificate to Fatbrain. Congratulations to our winner, Ngo the Duong. If you’d like to respond to these suggestions, please post a comment below. If you’d like to suggest a topic for a future quiz, please send us a note.

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