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Solutions for Common PC Problems

Various PC problem related solutions collected from newsgroups.

From alt.comp.hardware.pc-homebuilt FAQ

2.3 I built my own computer. It doesn't boot. Why not?

This is the crux of the homebuilder's dilemma. You've spent weeks selecting components, ordering them, painstakingly assembling a computer, and now the thing doesn't turn on. But you have no one to turn to since you built it yourself. Generally, the diagnosis is fairly straightforward, it depends on how far the computer gets into the boot process.

Try starting the system with only the following connected: motherboard power, case power switch (or motherboard power switch for ATX), speaker, CPU, memory, video card. Disconnect/remove all other peripherals.

Symptom                     Probable Causes
=======                     ===============

No power (power      motherboard shorted to case,
supply fan does      ATX power switch not connected,
not spin)            power supply bad

Power, no video,     speaker not connected, motherboard shorted to case, 
no POST beeps        CPU not seated, m/b power connector reversed
Power, POST beeps,   memory improperly seated or wrong type, video card
no video             improperly seated or bad. See BIOS manufacturer's
                     site for translation of beep code, or

Power, no beeps,     incorrect motherboard jumper settings, incorrect
video, no error      parameters - select "power on defaults" from BIOS
message              setup menu

Power, no beeps,     see http://www.pcguide.com/ts/x/sys/booterr.htm

error message        for translation of error message

Power, no beeps,     disk CHS parameters incorrect, incorrect
"missing operating   mode (LBA/ECHS), hard disk not partitioned and/or 
system" message      formatted, system files missing or corrupt

See the following for a very detailed boot troubleshooting procedure: http://www.pcguide.com/ts/x/boot/quick.htm. Here's another analysis procedure: http://www.computercraft.com/docs/pcanalysis.html

2.4 My homebuilt computer crashes. Why?

There a a great number of problems that can cause a computer to lock up or crash. The keys are to pay attention to the circumstances under which it happens, and what symptoms occur.

Crashes that reult in error messages can be due to bugs in the software. These can usually be reproduced by performing the same sequence of actions again.

System hard lock ups (no mouse movement or other activity) are usually caused by hardware/config problems. If the lock up occurs only after several minutes (and happens consistently) it is likely a problem with the motherboard power management or with insufficient cooling of the CPU.

The following sites provide insights and information on this topic: http://www.pcguide.com/ts/x/sys/crash.htm

If after reading these you come up with nothing, it is best to make note of all the circumstances surrounding the problem, symptoms and any error messages, then post to the newsgroup. Responses will usually be in terms of troubleshooting steps rather than outright answers.

2.5 How do I identify what motherboard I have?

When assembling a computer, you need to know how to set the jumpers, and to know what type of memory and CPUs it supports. This is difficult when you have a second-hand board and no manual.

The first thing to do is to have a close look at the motherboard and find the manfacturer name and model number. The model number is usually a short, aphanumeric string such as 486-PV/I or P55IT. 486 boards will often have "486" in the model number, and Pentium boards may have "P54" or

"P55". If you found the manufacturer name on the board, you can go to their web site and usually find a manual, or at least a summary of jumper settings. If you only found some candidate model numbers, it's time for more detective work.

I always start with doing a web search for the model number (http://www.altavista.com and http://www.hotbot.com seem to work particularly well for alphanumeric text searches). There is also a search engine at http://www.motherboards.org/ for this purpose. These may point you to the manufacturer web site directly.

In the case your motherboard is pre-web and the manufacturer has no copies of a manual or they went out of business, there are a few collections of motherboard manuals on the web.

If the computer boots already, you'll be able to find the model or at least the manufacturer by looking at the BIOS ID string that comes up on the boot screen. This is a long string of letters and numbers that may take a few tries to read (try adding a boot delay if you need time to write it down). A database of motherboard model numbers based on the BIOS id string can be found at: http://motherboards.mbarron.net/tables.htm

As a last resort, one can turn to the FCC OEM database. The FCC maintains a databse of manufacturers licenced to sell computer and communications products in the USA. If the component has an FCC ID number printed on it (and to be legal for sale in the US it does), you can track the manufacturer by searching the database at: http://www.fcc.gov/fcc-bin/ead. However, this may not give helpful results if the manufacturer turns out to be a tiny company in Hong Kong or Taiwan.

2.6 How do I transfer the files from my old hard disk?

New drives come with a utility to copy everything verbatim from the old drive; this software can also be downloaded from the manufacturer's web site. An alternative is commercial software such as Drive Copy and Ghost. Ghost is available as trialware. This software will usually allow you to partition and format your new drive easily.

Manually copying everything is another less foolproof option. See: http://www.computercraft.com/docs/doitrightwin95hd.html

Why does my system see all my memory above 16MB on POST but DOS only sees 16MB.

Answer: When installing more than 16MB of memory, BIOS relocation must be disabled. BIOS relocation copies the video BIOS (C0000-C7FFF) and the system ROM BIOS (F0000-FFFFF) into RAM. The motherboard (BIOS?) adds 15MB to these addresses (F00000) to be able to differentiate between the ROM and RAM. Enabling the relocation feature causes the memory above 16MB to become non-contiguous and therefore inaccessible. For DOS to size and utilize the memory above 16MB you MUST disable all BIOS and video ram relocation and/or caching settings in your CMOS setup. It may slow the system down somewhat but this is a throwback to the 286 memory limitation (24 bits) for 16MB of addressable memory.

2. My PS2 mouse won't work on my serial port with an adapter cable. My serial mouse won't work on my PS2 port with an adapter cable.

Answer: PS/2 mice and serial mice are two different devices. The ID bits returned from the mouse to the mouse detection S/W routine are different to differentiate the two devices. Mice labeled PS/2 port will ONLY work on a PS2 port. A mouse labeled serial mouse will only work on a serial port. Mice labeled PS2/Serial compatible (or a derivative thereof) can be adapted to work on either serial or mouse ports with the proper adapter cables(s). If your mouse has a single designator printed on the label on the bottom of the mouse then it is a single mode mouse.

Another twist on this problem are mice that have a slide switch on the bottom that reads MS or PC. MS is for Mouse Systems (Not Microsoft) and will not work without a Mouse Systems driver. If you have this switch on your mouse, set it to PC for standard mouse drivers.

3. Common causes of "Invalid drive specification" messages.

Answer: There are several sets of circumstances that can return this status.

A. If the drive has not been partitioned (with FDISK) this message will be reported.

B. If the drive parameters (Cyl, Hd, Sec) set in CMOS DON'T match those of the drive this message will be returned indicating that the drive geometry read from the drive doesn't match what is entered in CMOS.

C. General hardware failure on the disk sub-system where the drive geometry cannot be read (causing the mismatch described in B). This could be a bad cable, misplaced cable (off by a pin or row) no DC power to the disk, bad disk PCB, incorrect jumpering on disk PCB. Any matter of problems that can cause the disk to be unreadable can return this error message.

NOTE!! On initial HDD install/upgrade I'd do a physical check on all the obvious things like cable placement, power connectors, listen to hear the disk seeking during it's POST test on pwr up. If this error occurs after the disk has been operating normally it is indicative of a failure of some type. May be hardware failure, or partition data may have been corrupted. This is NOT a good message to get from a working drive.

4. My motherboard/system doesn't recognize 8MB SIMM's when I install them.

Answer: 2MB/8MB and 32MB SIMM's are what are know as "dual density" SIMM's. They are really two 1MB/4MB/16MB banks mounted on one SIMM PCB. In order to utilize "dual density" SIMM's the memory controller MUST support dual RAS(Row Address Select) and dual CAS(Column Address Select) functions. Many memory controllers DO not support dual RAS/CAS strobing. In this case the SIMM MAY be recognized as 4MB or not recognized at all.

If your MB manual doesn't list 2MB/8MB/32MB memory SIMM's in the memory matrix chart then it probably doesn't support "dual density" SIMM's. General rule of thumb is that "dual density" SIMM's will have components mounted on both sides of the SIMM PCB.

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