FAQ

1.     What is the maximum length of a network cable?
2.     What is the maximum length of a USB cable?
3.     Which memory type fits my PC?
4.     What is the maximum length of an IDE-cable?
5.     Notebook keyboard/mini keyboard error: I'm getting numbers instead of letters when writing.
6.     Which IRQ is which?
7.     Why does the touchscreen lose positional accuracy near the screen border?
8.     Does my computer support USB-devices?
9.     What is a transmissive TFT-display?
10.     Hard disk capacity is smaller than expected
11.     My PC fails to boot with the following error message: "DISK BOOT FAILURE, INSERT SYSTEM DISK AND PRESS ENTER"?
12.     Not enough time to view the boot list during the system power-up?
13.     Two or more beeps during the power-up sequence?
14.     No picture on the computer display?
15.     The floppy disk drive's indicator LED stays constantly on?
16.     What is the reason for Windows 2000 System Log error:"The driver detected a controller error on \Device\Harddisk\DR0"?
17.     orlogix Backup MyPC Error Message "The device received an invalid command. Ref: 05-20-23-00-8081"
18.     Error message when trying to open CEF Diagnostics Helpfile? (HHCTRL.OCX)
19.     Yosemite Technologies TapeWare XD Desktop Edition installation fails in Windows NT 4.0? (SHLWAPI.dll)
20.     VERITAS Backup Exec Desktop Edition Error Message "The device received an invalid command. Ref: 05-20-23-00-8081"

1. What is the maximum length of a network cable?

• Copper cable (Unshielded twisted pair, UTP)

• Fiber optic cable

2. What is the maximum length of a USB cable?

Three or five meters, depending on the type of the device.

Slow devices (mice, gamepads...) only use a 1.2 Mb/s subchannel of the bus. These devices have a maximum cable length of 3 m (approx. 10 ft). The slow devices usually take their current from the USB cable.

Fast devices use the full speed of the bus (Full speed USB 12 Mb/s or High speed USB 480 Mb/s) and are able to connect using a 5 m cable (approx. 16 ft). Fast devices usually have their own power connection.

If you need longer reach, the USB cables may be daisychained using no more than five USB hubs. Five hubs connected with 5 m cables and with a 5 m cable to a full speed device gives you a theoretical maximum length of 30m. With a low speed device, you'll get a 28 m cable.
 

3. Which memory type fits my PC?

The best place to look for correct information about the memory types is in the documentation provided with your processor card/mainboard. If you have displaced your documentation, the website of the manufacturer can usually provide downloadable replacements. Here is a short introduction to the most common memory types.

30-pin_SIMM
Short SIMM, length approx. 3" (7,5 cm), 30 pins, no notches

A PC based on 386 processor (or earlier) normally uses short 30-pin SIMMs (Single Inline Memory Module). Typical sizes for SIMM modules are 512 kB, 1 MB and 4 MB. Usually the modules are applied four at a time for all four memory slots on the processor card, so there are no compatibility issues. The maximum memory for a computer using short SIMMs is normally 16 MB or below.

72-pin_SIMM
Long SIMM, length approx. 4" (10 cm), 72 pins, one notch

486 and Pentium based PCs use 72-pin long SIMM modules. Due to the width of the processor's memory bus, for Pentium machines the SIMM modules are applied two at a time. SIMM memory is available in many types and speeds, which usually are compatible with each other. If different types of SIMMs are used at the same time, all of the memory will function at the speed of the slowest module. Two of the most common types are FPM (Fast Page Mode) and faster EDO (Extended Data Out). The maximum speed of SIMM memory is 66 MHz.

SDRAM-DIMM
SDRAM DIMM, length approx. 5" (13 cm), 168 pins, two notches

Pentium II-III and AMD K6-2/Duron/Athlon based micros usually accept DIMMs (Dual Inline Memory Module). The memory bus of a DIMM module is 64 bits wide, so they can be added one at a time for Pentium machines.

The clock frequency of DIMM memory is 66, 100 or 133 MHz. Almost all modern DIMMs are SDRAM (Synchronous dynamic RAM) DIMMs, but older EDO is also available. The backward compatibility of DIMM memory is usually good, so modules of different speeds can be used together. All of the memory modules will then work at the speed of the slowest module.

DDR
DDR DIMM, length approx. 5" (13 cm), 184 pins, one notch

Pentium III-4 and Athlon XP based PCs usually accept DDR (Dual Data Rate) memory modules. DDR is SDRAM memory, which is speeded up by reading data on both the rising and falling edges of the system's clock signal instead of only on the rise as with normal SDRAM memory. DDR memory speed is typically in the range of 266 - 400 MHz. The memory is often sold under names PC1600 (speed 200 MHz), PC2100 (266 MHz) and PC2600 (333 MHz).

DDR memory is not very compatible. It is not recommended to use modules of different speeds at the same time. Using modules with components on both sides together with one-sided modules can also cause trouble. And even memory modules with same specifications, but from different manufacturers may not work together well.

RIMM
RIMM (Rambus), length approx. 5" (13 cm), 184 pins, two notches, heat-spreader packaged

RIMM (Rambus Inline Memory Module) is an alternative memory technology to DDR. The clock frequency of RIMM is up to 800 MHz. The speed of the memory is offset by a 16-bit narrow memory bus, so in use RIMM is not a lot faster than DDR memory. It is a lot more expensive, so DDR offers better bang per buck. RIMM modules are easy to recognize because they have metallic heat-spreaders covering the components.

SO-DIMM
SO-DIMM, length approx 3" (7 cm), commonly used in notebooks

Notebook computers usually accept SO-DIMM memory modules. This is normal SDRAM DIMM packaged in a very small format. Corresponding SO-RIMMs are also available.
 

4. What is the maximum length of an IDE-cable?

According to the ATA standards the IDE-cable maximum length is 18 inches (45,7 cm).

40-wire IDE-cable used with older and slower hard disks and CD-ROMs may work even if it is longer than the standard assigned maximum. 80-wire cables used with newer and faster Ultra-ATA devices will very propably fail to work at all if longer than 18 inches.

 

A2 length shall be greater than or equal to A3
 

5. Notebook keyboard/mini keyboard error: I'm getting numbers instead of letters when writing.

You have unintentionally pressed the NumLock key.

Because there is no room for separate numeric keys on the notebook, some letter keys have the ability to function as a numeric pad when the "NumLock" key is pressed. To get the behaviour back to normal, press NumLock key again.

6. Which IRQ is which?

7. Why does the touchscreen lose positional accuracy near the screen border?

The touchscreen top layer is made of a polyester coversheet, which is a separate element attached to the glass panel below from all four sides. This structural detail is the reason for the lessening of positional accuracy on the touchscreen border areas, also known as the scalloping effect.

To demonstrate the scalloping effect, draw with a finger along the edge of the touchscreen, as close to the display frame as you can. Instead of following your finger in a straight line, the cursor moves in an easily distinguishable saw-edge motion.

Touchscreen loses positional accuracy
 

8. Does my computer support USB-devices?

USB support is included in Microsoft Windows 98, Me, 2000, XP and newer. A limited support for USB is available for Windows 95 version 4.00.950B and newer via Microsoft Windows 95 USB Supplement program, which is supplied on the Win95 CD-rom but not installed by default.

As a rule Windows NT4 and earlier NT versions do not support USB devices. Some manufacturers may offer USB drivers working with specific devices.

Linux has USB support since kernel version 2.2.18. USB support is included in 2.4-series and newer kernels.

Sun Microsystems Solaris-operating system supports USB-devices since version 8.
 

9. What is a transmissive TFT-display?

There are three different types of TFT-displays. The types are:

Reflective An external light source from the front of the display is used for illumination. This makes reflective displays easy to manufacture and also makes them draw a lot less power than the other two types. The picture on a reflective display gets better when the environment's light level goes up. This type of display is used mostly in small, portable devices because their position can easily be adjusted to take advantage of the lighting conditions. Reflective displays are well suitable for outdoor use.

Transmissive An internal light source from the back (or side) of the display is used for illumination. Bright light, e.g. direct sunlight, causes reflections which make the display almost unreadable and 'washed out'. On the other hand transmissive displays can be easily used in dim or even dark conditions. Because of their excellent brightness and contrast, transmissive displays are typically used indoors as desktop computer monitors.

Transflective Combines the best of both transmissive and reflective displays. The light source can be either from the front (sun, lamp, ambient light) or back (backlighting). Transflective displays are easy to use both indoors and outdoors. The backlighting can be turned on only when needed, which saves batteries on mobile devices. The technology used in manufacturing transflective displays is currently quite expensive, so these types of displays are found only in high-end notebooks like the Panasonic Toughbook line.

10. Hard disk capacity is smaller than expected

Since the dawn of computing, the standard definition for a megabyte has been two to the 20th power bytes (1 048 576 bytes), which is easily represented in shorthand form 220. A gigabyte is 230 bytes (1 073 741 824).

So you would expect a brand new 60 gigabyte disk to have a capacity of 60 X 230 bytes = 64 424 509 440 bytes. However, your system BIOS, the disk utilities you use and Windows Explorer all state that the capacity of your hard disk is only a little under 56 GB. Where did the missing four gigabytes vanish?

The hard drive manufacturers have redefined a megabyte as 1 000 000 bytes and a gigabyte as 1 000 000 000 bytes. This is a decimal, base 10, number and is widely known as marketing standard. As the marketing standard gigabyte is smaller than the real one, you can fit more of them in a same capacity hard disk, resulting in hard disk size elevation.

The 60 GB hard disk you bought came with 60 billion (decimal) bytes instead of 64+ billion. 60 000 000 000 bytes correspond to little less than 56 real binary Gigabytes, which is what your utilities have been telling you all along.

Few examples of how various drive capacities will change:

11. My PC fails to boot with the following error message: "DISK BOOT FAILURE, INSERT SYSTEM DISK AND PRESS ENTER"?

The PC can not find the operating system's boot files.

One common reason for this error message is a non-bootable floppy left in the floppy drive during startup in combination with "floppy first" selection in the BIOS boot order.

12. Not enough time to view the boot list during the system power-up?

Use the Pause/Break-key on the keyboard to stop the system from powering up. This will give you more time to peruse the list. Press Enter to reboot your machine after you are ready.

13. Two or more beeps during the power-up sequence?

During power-up, the computer goes through a Power On Self Test (POST) sequence, which quickly checks the components (memory etc.) and devices (mouse, keyboard etc.). If a fault is found during the POST, the boot process is halted and a signal is sent out as a certain amount of beeps through the computer buzzer. The beep code reveals the location of the problem. Every BIOS maker has its own beep code, which is available from the BIOS manufacturer's website. If no errors are found during the POST, the computer usually gives only one short beep.

14. No picture on the computer display?

Always check the power and signal cables' condition and their connections first. If the monitor stays blank try following hints:

• If the LEDs on the motherboard show that correct voltage is available, the power supply is probably working OK.
• No beeps at all during the power-up means that the CPU, the memory or the processor card is either not properly seated or is faulty.
• Exactly one beep means that the display or the display cable is faulty.
• Two or more beeps mean that there is a problem with the graphics adapter or some other peripheral device. Try reseating the graphics adapter first. If this does not help, remove other expansion cards, external cables and devices and try again.
• One possible (but rare) cause for a blank screen is hard disk cable that is connected the wrong way.
  
   

15. The floppy disk drive's indicator LED stays constantly on?

The most common cause for a constantly glowing floppy drive LED is the data cable being connected the wrong way up.

If you have only one floppy disk drive, you should always use the connector with wires 10-16 twisted, leaving the middle connector free. There is a red or blue coloured stripe on one edge of the cable, corresponding to pin one on the floppy drive connector.

The LED will also glow constantly if you have forced the power connector upside down, crossconnecting +5 and +12 V. This will probably destroy the floppy disk drive beyond repair.
 

16. What is the reason for Windows 2000 System Log error:"The driver detected a controller error on \Device\Harddisk\DR0"?

• No chipset specific IDE-drivers installed -> install IDE-drivers. The drivers can usually be found on a CD supplied by your processor card/motherboard manufacturer or they may be downloaded from the internet.
• An Ultra-ATA (Ultra-DMA) hard disk is connected using a 40-wire IDE cable -> replace with an 80-wire cable or change the bus settings to a PIO mode: Device Manager -> IDE ATA/ATAPI controllers -> doubleclick Primary IDE Channel -> Advanced Settings -tab -> Change Transfer Mode -fields to PIO Only.
   

17. orlogix Backup MyPC Error Message "The device received an invalid command. Ref: 05-20-23-00-8081"

The most probable reason for this error message is that the inserted tape's size is not supported by the tape drive. Replace the tape cartridge and rerun your backup batch file.

18. Error message when trying to open CEF Diagnostics Helpfile? (HHCTRL.OCX)

This problem can occur if your system either does not have the HTMLHelp viewer installed or has an older version of the HTMLHelp viewer. The viewer is upgraded automatically alongside Internet Explorer browser. The systems affected have Internet Explorer 4 sp1 or earlier. Please upgrade your browser to at least IE5 or download the latest HTMLHelp update for IE4 from Microsoft.

19. Yosemite Technologies TapeWare XD Desktop Edition installation fails in Windows NT 4.0? (SHLWAPI.dll)

The error message "The dynamic link library SHLWAPI.dll could not be found..." is caused by an obsolete version of the Internet Explorer in your system. Please upgrade your browser to at least IE4, preferably IE5+.

20. VERITAS Backup Exec Desktop Edition Error Message "The device received an invalid command. Ref: 05-20-23-00-8081"

The most probable reason for this error message is that the inserted tape's size is not supported by the tape drive. Replace the tape cartridge and rerun your backup batch file.