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| | | | FAQ Revisions | Editors: Cariad  , vkr , dragon , dbmaven
Last modified on 2008-05-05 11:15:42
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3.1 Terms/Definitions·What is this BUS thing I keep hearing about?
·What is PCMCIA?
·What is CNR?
·What is POST (Power On Self Test)
·What is BIOS?
·What in the world does OEM mean?
·What are IRQ Numbers?
·What is an IDE 80 conductor cable
·What is USB?
·What is DMA?
·IDE Devices:Master, Slave, or Cable Select?
| | | A very detailed explanation of all the busses inside your system, and how they interact:
System Busses and their interaction
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by dbmaven
last modified: 2003-10-15 19:32:34 | | | Short for Personal Computer Memory Card International Association, and pronounced as separate letters, PCMCIA is an organization consisting of some 500 companies that has developed a standard for small, credit card-sized devices, called PC Cards. Originally designed for adding memory to portable computers, the PCMCIA standard has been expanded several times and is now suitable for many types of devices. There are in fact three types of PCMCIA cards. All three have the same rectangular size (85.6 by 54 millimeters), but different widths
As with the cards, PCMCIA slots also come in three sizes:
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by redxii edited by dbmaven
last modified: 2003-09-05 11:05:36 | | | Communication Networking Riser
Link no longer active - October 2003.
Information about the Communications and Networking Riser appears to have been removed from the INTEL site.
It appears that it has now passed semi-officially into the realm of "dead standards".
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by Raj Dynel edited by dbmaven
last modified: 2003-10-12 01:10:31 | | | When you switch on your system, it runs a series of diagnostic tests, collectively called the Power-on Self-Test (POST). POST makes sure the following computer parts are functioning properly:
•Keyboard
•Power supply
•System board
•System memory
•Memory modules
•Controllers
•Graphics system
•Diskette drives
•Hard drives
POST also detects the type of mass storage devices installed in the computer. If POST finds an error in the system, it reports the error condition by an audible Beep Code and/or visual message. Once POST is complete it will proceed to the BIOS startup screen.
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by vkr edited by dbmaven
last modified: 2003-09-05 11:02:14 | | | What is BIOS?
Q: What is BIOS?
A: BIOS stands for Basic Input Output System.
All computer hardware has to work with software through an interface. The BIOS gives the computer a little built-in starter kit to run the rest of softwares from floppy disks (FDD) and hard disks (HDD). The BIOS is responsible for booting the computer by providing a basic set of instructions. It performs all the tasks that need to be done at start-up time: POST (Power-On Self Test, booting an operating system from FDD or HDD). Furthermore, it provides an interface to the underlying hardware for the operating system in the form of a library of interrupt handlers. For instance, each time a key is pressed, the CPU (Central Processing Unit) perform an interrupt to read that key. This is similar for other input/output devices (Serial and parallel ports, video cards, sound cards, hard disk controllers, etc...). Some older PC's cannot co-operate with all the modern hardware because their BIOS doesn't support that hardware. The operating system cannot call a BIOS routine to use it; this problem can be solved by replacing your BIOS with an newer one, that does support your new hardware, or by installing a device driver for the hardware.
Q: Well, I see that the BIOS is necessary for the computer, but what can I do with it?
A: You can change hardware configurations that are stored in the CMOS, or Complementary Metal Oxide Semiconductor.
To perform its tasks, the BIOS need to know various parameters (hardware configuration). These are permanently saved in a little piece (64 bytes) of CMOS RAM (short: CMOS). The CMOS power is supplied by a little battery, so its contents will not be lost after the PC is turned off. Therefore, there is a battery and a small RAM memory on board, which never (should...) lose its information. The memory was in earlier times a part of the clock chip, now it's part of such a highly Integrated Circuit (IC). CMOS is the name of a technology which needs very low power so the computer's battery is not too much in use.
Your PC's performance can be highly affected by the CMOS settings. The reason for this is that the CMOS setup allows you to specify how fast your computer reads from memory, whether or not your cache is enabled or disabled, whether or not your CPU's cache is enabled or disabled, how fast your PCI bus communicates with its adaptor cards, plus a lot more. For more information on optimizing these performance settings/
Additionally, the CMOS setup allows you to specify disk drive and memory configuration. In order for your hard drive to work with your system, it must be configured in the CMOS setup. The exception to that rule is SCSI drives with adaptor cards, as most have their own built in BIOS. Floppy drives can be setup in the CMOS as well; a: can be made to be b: in many systems, and other configuration options can be changed as well.
Q: So how do I change the configuration that is saved in the CMOS?
A: By utilizing a set of menus called the CMOS Setup.
Setup is the set of procedures enabling the configure a computer according to its hardware caracteristics. It allows you to change the parameters with which the BIOS configures your chipset. The original IBM PC was configured by means of DIP switches buried on the motherboard. Setting PC and XT DIP switches properly was something of an arcane art. DIP switches/jumpers are still used for memory configuration and clock speed selection. When the PC-AT was introduced, it included a battery powered CMOS memory which contained configuration information. CMOS was originally set by a program on the Diagnostic Disk, however later clones incorporated routines in the BIOS which allowed the CMOS to be (re)configured if certain magic keystrokes were used.
Unfortunately as the chipsets controlling modern CPUs have become more complex, the variety of parameters specifiable in SETUP has grown. Moreover, there has been little standardization of terminology between the half dozen BIOS vendors, three dozen chipset makers and large number of motherboard vendors. Complaints about poor motherboard documentation of SETUP parameters are very common.
To exacerbate matters, some parameters are defined by BIOS vendors, others bychipset designers, others by motherboard designers, and others by various combinations of the above. Parameters intended for use in Design and Development, are intermixed with parameters intended to be adjusted by technicians -- who are frequently just as baffled by this stuff as everyone else is. No one person or organization seems to understand all the parameters available for any given SETUP.
Q: Now that I know where to edit the CMOS options, how do I access this CMOS setup on my computer?
A: By entering a keystroke combination when the system is first booted.
When the system is powered on, the BIOS will perform diagnostics and initialize system components, including the video system. (This is self-evident when the screen first flicks before the Video Card header is displayed). This is commonly referred as POST (Power-On Self Test). Afterwards, the computer will proceed its final boot-up stage by calling the operating system. Just before that, the user may interrupt to have access to SETUP.
Usually, setup can be entered by pressing a special key combination (DEL, ESC, CTRL-ESC, or CTRL-ALT-ESC) at boot time (Some BIOSes allow you to enter setup at any time by pressing CTRL-ALT-ESC). The AMI BIOS is mostly entered by pressing the DEL key after resetting (CTRL-ALT-DEL) or powering up the computer. You can bypass the extended CMOS settings by holding the key down during boot-up. This is really helpful, especially if you bend the CMOS settings right out of shape and the computer won't boot properly anymore. This is also a handy tip for people who play with the older AMI BIOSes with the XCMOS setup. It allows changes directly to the chip registers with very little technical explanation.
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by FastEddie edited by dbmaven
last modified: 2003-09-05 11:29:14 | | | OEM stands for Original Equipment Manufacturer. It signifies that the particular version of that product does not come with a retail box. Installation instructions are typically loaded on a disk or CD rather than in a printed manual, although, depending on the manufacturer, you may receive a printed manual as well.
OEM software products are generally required to be sold or bundled with hardware - Hard Drives, CPUs, etc. OEM does NOT mean an item is recycled or refurbished. We encourage you to contact the product manufacturer if you have any further questions or concerns regarding OEM products.
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by redxii edited by dbmaven
last modified: 2003-09-05 11:03:02 | | | IRQ DETAILS BY NUMBERS
This section lists each of the 16 interrupt lines and provides a full description of what they are, how they are normally used, and any special information that is relevant to them. The general format for each section is as follows:
IRQ Number: The number of the IRQ from 0 to 15.
16-Bit Priority: The priority level of the interrupt. 1 is the highest and 15 is the lowest.
Bus Line: Indicates whether or not this IRQ is available to expansion devices on the system bus. This will say "8/16 bit" for an interrupt line available to all expansion devices, "16 bit only" for a line available only to 16-bit cards, or "No" for an interrupt used only by system devices.
Typical Default Use: Description of the device or function that normally uses this IRQ in a regular modern PC.
Other Common Uses: This is a list of other devices that commonly either use this IRQ or offer the use of this IRQ as one of their options. This list isn't exhaustive because there are a lot of oddball cards out there that may use unusual IRQs.
Description: A description of the interrupt and how it is used, along with any relevant or interesting points about it or its history.
Conflicts: A discussion of the likelihood of conflicts with this IRQ and what are the likely causes.
•IRQ 0
IRQ Number: 0
16-Bit Priority: 1
Bus Line: No
Typical Default Use: System timer.
Other Common Uses: None; for system use only.
Description: This is the reserved interrupt for the internal system timer. It is used exclusively for internal operations and is never available to peripherals or user devices.
Conflicts: This is a dedicated interrupt line; there should never be any conflicts. If software indicates a conflict on this IRQ, there is a good possibility of a hardware problem somewhere on your system board.
•IRQ 1
IRQ Number: 1
16-Bit Priority: 2
Bus Line: No
Typical Default Use: Keyboard / keyboard controller.
Other Common Uses: None; for system use only.
Description: This is the reserved interrupt for the keyboard controller. It is used exclusively for keyboard input. Even on systems without a keyboard, IRQ1 is not available for use by other devices. Note that the keyboard controller also controls the PS/2 style mouse if the system has one, but the mouse uses a separate line, IRQ12.
Conflicts: This is a dedicated interrupt line; there should never be any conflicts. If software indicates a conflict on this IRQ, there is a good possibility of a hardware problem somewhere on your system board; this can be a motherboard or chipset (keyboard controller) problem.
•IRQ 2
IRQ Number: 2
16-Bit Priority: n/a
Bus Line: No
Typical Default Use: Cascade for IRQs 8 to 15.
Other Common Uses: Not generally used. Can be used by modems, very old (EGA) video cards, as an alternative IRQ for COM3 (third serial port) or COM4 (fourth serial port). Rerouted to IRQ9 and appears to software as IRQ9.
Description: This is the interrupt number that is used to cascade the second interrupt controller to the first, allowing the use of extra IRQs 8 to 15. This use as a linkage between the two interrupt controllers means that IRQ2 is no longer available for normal use. For compatibility with older cards that used IRQ2 on the original PC or XT machines (which had only one controller and a normal IRQ2 line), the motherboard of modern PCs reroutes IRQ2 to IRQ9. Hence IRQ2 can still be used but appears to the system as IRQ9. The most common cards that do this are old EGA video cards, and newer cards making IRQ2 available with the knowledge that it will be routed to IRQ9.
Conflicts: This interrupt is normally not used on most systems, mostly because the whole IRQ2/IRQ9 thing confuses a lot of people so they tend to avoid it. Conflicts on this line generally come from trying to use a device on IRQ2 and another on IRQ9 at the same time. Some modems and serial port cards allow IRQ2 to be used as an alternative for the two standard lines used for modems and serial ports (IRQ3 and IRQ4) in order to avoid conflicts in those two heavily-contested areas. This is generally a good configuration decision since unused IRQs from 3 to 7 are harder to find than unused IRQs from 10 to 15. If you want to use IRQ2, move any device using IRQ9 to another line like 10 or 11.
•IRQ 3
IRQ Number: 3
16-Bit Priority: 11
Bus Line: 8/16-bit
Typical Default Use: COM2 (second serial port).
Other Common Uses: COM4 (fourth serial port), modems, sound cards, network cards, tape accelerator cards.
Description: This interrupt is normally used by the second serial port, COM2. It is also the default interrupt for the fourth serial port, COM4, and a popular option for modems, sound cards and other devices. Modems often come pre-configured to use COM2 on IRQ3.
Conflicts: Conflicts on IRQ3 are relatively common. The two biggest problem areas are first, modems that attempt to use COM2/IRQ3 and clash with the built-in COM2 port; and second, systems that attempt to use both COM2 and COM4 simultaneously on this same interrupt line. In addition, some devices, particularly network interface cards, come with IRQ3 as the default. In most cases the problem can be avoided by changing the conflicting device to a different interrupt (IRQ2 and IRQ5 usually being the best choices). If the built-in COM2 is not being used, it can be disabled in the BIOS setup, which will allow a modem to stay at COM2/IRQ3 without causing any problems. More general solutions to these issues can be found in the conflict resolution area of the Troubleshooting Expert.
•IRQ 4
IRQ Number: 4
16-Bit Priority: 12
Bus Line: 8/16-bit
Typical Default Use: COM1 (first serial port).
Other Common Uses: COM3 (third serial port), modems, sound cards, network cards, tape accelerator cards.
Description: This interrupt is normally used by the first serial port, COM1. On PCs that do not use a PS/2-style mouse, this port (and thus this interrupt) are almost always used by the serial mouse. IRQ4 is also the default interrupt for the third serial port, COM3, and a popular option for modems, sound cards and other devices. Modems sometimes come pre-configured to use COM3 on IRQ4.
Conflicts: Conflicts on IRQ4 are relatively common, although not as common as on IRQ3. On systems that do not use a serial mouse, problems are less common, because COM1 isn't automatically busy whenever the mouse is in use. The two biggest problem areas are modems that attempt to use COM3/IRQ4 and clash with COM1, and systems that attempt to use both COM1 and COM3 simultaneously on this same interrupt line. In most cases the problem can be avoided by changing the conflicting device to a different interrupt (IRQ2 and IRQ5 usually being the best choices). If a PS/2 mouse is being used, you can disable the built-in COM1 port in the BIOS setup, which will allow a modem to stay at COM3/IRQ4 without causing any problems. However, this is not really recommended. More general solutions to these issues can be found in the conflict resolution area of the Troubleshooting Expert.
•IRQ 5
IRQ Number: 5
16-Bit Priority: 13
Bus Line: 8/16-bit
Typical Default Use: Sound card (but varies widely).
Other Common Uses: LPT2 (second parallel port), COM3 (third serial port), COM4 (fourth serial port), modems, network cards, tape accelerator cards, hard disk controller on old PC/XT.
Description: This is probably the single "busiest" IRQ in the whole system. On the original PC/XT system this IRQ was used to control the (massive 10 MB) hard disk drive. When the AT was introduced, hard disk control was moved to IRQ14 to free up IRQ5 for 8-bit devices. As a result, IRQ5 is in most systems the only free interrupt below IRQ9 and is therefore the first choice for use by devices that would otherwise conflict with IRQ3, IRQ4, IRQ6 or IRQ7. IRQ5 is the default interrupt for the second parallel port in systems that use two printers for example. It is also the first choice that most sound cards make when looking for an IRQ setting. IRQ5 is also a popular choice as an alternate line for systems that need to use a third COM port, or a modem in addition to two COM ports.
Conflicts: Conflicts on IRQ5 are very common because of the large variety of devices that have it as an option. Since virtually every PC today uses a sound card, and they all like to grab IRQ5, it is almost always taken before you even start looking at more esoteric peripherals. If a second parallel port (LPT2) is being used to allow access to two printers or a printer and a parallel-port drive, then IRQ5 will usually be taken right away. If for some very strange reason you have three parallel ports, watch for a conflict here or with IRQ7, since 5 and 7 are the only two normally used as defaults for parallel ports. Sound cards that default to IRQ5 are generally best left there, to avoid problems with poorly written older software that just assumed the sound card would always be left at IRQ5. To whatever extent possible, move devices that can use higher-valued IRQs away from IRQ5. For example, you can't move COM3 to IRQ11, but you usually can move a network card to it. See the conflict resolution area of the Troubleshooting Expert for more ideas.
•IRQ 6
IRQ Number: 6
16-Bit Priority: 14
Bus Line: 8/16-bit
Typical Default Use: Floppy disk controller.
Other Common Uses: Tape accelerator cards.
Description: This interrupt is reserved for use by the floppy disk controller. Technically, it is available for use by other devices, and some devices will allow you to select IRQ6. Most however do not, realizing that virtually every PC uses at least one floppy disk drive. The most common devices that will let you use IRQ6 are probably tape drive accelerator cards. This is probably because these cards are used for tape drives that run off the floppy interface, and many of them can be set to drive floppy disks themselves.
Conflicts: Conflicts on IRQ6 are uncommon and are usually the result of an incorrectly configured peripheral card, since IRQ6 is pretty standardized in its use for the floppy disks. If you use a tape accelerator card along with an integrated floppy disk controller on your motherboard, watch out for the accelerator trying to take over IRQ6; some even do this by default.
•IRQ 7
IRQ Number: 7
16-Bit Priority: 15
Bus Line: 8/16-bit
Typical Default Use: LPT1 (first parallel port).
Other Common Uses: COM3 (third serial port), COM4 (fourth serial port), modems, sound cards, network cards, tape accelerator cards.
Description: This IRQ is used on most systems to drive the first parallel port, normally for the use of a printer. These days of course many other devices use parallel ports, including external drives. If you are not using a printer or other device then IRQ7 can be used in a similar way to IRQ5: as an alternate for any of the devices that would normally be fighting over IRQ3 or IRQ4.
Conflicts: Conflicts on IRQ7 are relatively unusual. One thing to watch out for if you are using two parallel ports is to make sure the second one is set up to use IRQ5 or another available IRQ. Some add-in parallel boards try to make LPT2 also use IRQ7, which generally won't work. Otherwise, avoiding using IRQ7 for an expansion card if you are using it for LPT1 will eliminate conflicts in most cases.
•IRQ 8
IRQ Number: 8
16-Bit Priority: 3
Bus Line: No
Typical Default Use: Real-time clock.
Other Common Uses: None; for system use only.
Description: This is the reserved interrupt for the real-time clock timer. This timer is used by software programs to manage events that must be calibrated to real-world time; this is done by setting "alarms", which trigger this interrupt at a specified time. For example, if you are using an electronic datebook and have it set to pop up screen messages or beep the PC when it is time for a meeting, the software will set a timer to count down to the appropriate time. When the timer finishes its countdown, an interrupt will be generated on IRQ8.
Conflicts: This is a dedicated interrupt line; there should never be any conflicts. If software indicates a conflict on this IRQ, there is a good possibility of a hardware problem somewhere on your system board.
•IRQ 9
IRQ Number: 9
16-Bit Priority: 4
Bus Line: 16-bit only
Typical Default Use: None.
Other Common Uses: Network cards, sound cards, SCSI host adapters, PCI devices,
rerouted IRQ2 devices.
Description: This is usually an open IRQ on most systems, and is a popular choice for use by peripherals, especially network cards. On most PCs it can be used freely since it has no default setting.
Conflicts: There are a couple of things to watch out for when using this IRQ. First, if you are trying to use IRQ2, you cannot use IRQ9 as well, since devices that try to use IRQ2 really end up using IRQ9 instead. Also, some systems that use PCI cards that require the use of a system IRQ line will grab IRQ9; this can be changed in some cases using the BIOS setup parameters that assign IRQs to PCI devices.
•IRQ 10
IRQ Number: 10
16-Bit Priority: 5
Bus Line: 16-bit only
Typical Default Use: None.
Other Common Uses: Network cards, sound cards, SCSI host adapters, secondary IDE channel, quaternary IDE channel, PCI devices.
Description: This is usually open and one of the easiest IRQs to use since it is generally not contested by many devices. While the secondary IDE controller can sometimes be set to use IRQ10, it almost always uses IRQ15 instead.
Conflicts: Conflicts on IRQ10 are unusual; the only thing to watch out for is a PCI card that needs an interrupt line being assigned IRQ10 by the BIOS; this can be changed in some cases using the BIOS setup parameters that assign IRQs to PCI devices.
•IRQ 11
IRQ Number: 11
16-Bit Priority: 6
Bus Line: 16-bit only
Typical Default Use: None.
Other Common Uses: Network cards, sound cards, SCSI host adapters, VGA video cards, tertiary IDE channel, quaternary IDE channel, PCI devices.
Description: This line is usually open and relatively easy to use since it is generally not contested by many devices. If you are using three IDE channels (the third typically being on a sound card), IRQ11 is typically the one that the tertiary controller will try to use. Also, some PCI video cards will try to use IRQ11.
Conflicts: Watch out for PCI cards, especially video cards, that grab IRQ11. This can be changed in some cases using the BIOS setup parameters that assign IRQs to PCI devices.
•IRQ 12
IRQ Number: 12
16-Bit Priority: 7
Bus Line: 16-bit only
Typical Default Use: PS/2 mouse.
Other Common Uses: Network cards, sound cards, SCSI host adapters, VGA video cards, tertiary IDE channel, PCI devices.
Description: On machines that use a PS/2 mouse, this is the IRQ reserved for its use. Using a PS/2 mouse frees up the COM1 serial port and the interrupt it uses (IRQ4) for other devices. Normally this is a good trade since free IRQs with numbers below 8 are harder to find than ones above 8. If a PS/2 mouse is not used, IRQ12 is a good choice for use by
other devices such as network cards.
Conflicts: There are some potential problems here. Watch out for PCI cards that can sometimes be assigned this line by the system BIOS. This can be changed in some cases using the BIOS setup parameters that assign IRQs to PCI devices. If you are using a PS/2 mouse you need to make sure no other devices use IRQ12.
•IRQ 13
IRQ Number: 13
16-Bit Priority: 8
Bus Line: No
Typical Default Use: Floating point unit (FPU / NPU / Math coprocessor).
Other Common Uses: None; for system use only.
Description: This is the reserved interrupt for the integrated floating point unit (on 80486 or later machines) or the math coprocessor (on 80386 or earlier machines that use one). It is used exclusively for internal signaling and is never available for use by peripherals.
Conflicts: This is a dedicated interrupt line; there should never be any conflicts. If software indicates a conflict on this IRQ, there is a good possibility of a hardware problem somewhere on your system board, or possibly with your processor or math coprocessor.
•IRQ 14
IRQ Number: 14
16-Bit Priority: 9
Bus Line: 16-bit only
Typical Default Use: Primary IDE channel.
Other Common Uses: SCSI host adapters.
Description: On most PCs, this IRQ is reserved for use by the primary IDE controller, which provides access to the first two IDE/ATA devices (usually hard disk drives and/or CD-ROM drives). On machines that do not use IDE devices at all, this IRQ can be used for another purpose (such as a SCSI host adapter to provide SCSI drives). In order to do this, you will normally have to disable the IDE channel using either the appropriate BIOS setting (for integrated IDE support on newer boards) or jumpers on the controller board (for older machines that use an IDE controller card).
Conflicts: Problems with IRQ14 are rare, since the universality of its use for IDE means most peripheral vendors avoid offering it as an option. If you are using SCSI and not IDE, and want to use IRQ14, make sure any integrated IDE controllers are disabled first.
•IRQ 15
IRQ Number: 15
16-Bit Priority: 10
Bus Line: 16-bit only
Typical Default Use: Secondary IDE channel.
Other Common Uses: Network cards, SCSI host adapters.
Description: On most newer PCs, this IRQ is reserved for use by the secondary IDE controller, which provides access to the third and fourth IDE/ATA devices (usually hard disk drives and/or CD-ROM drives). If you are not using IDE, or are using only two devices and want to put them on the primary channel to free up this IRQ, that can be done easily as long as you remember to disable the secondary IDE channel using either the appropriate BIOS setting (for integrated IDE support on newer boards) or jumpers on the controller board (for older machines that use an IDE controller card).
Conflicts: Problems with IRQ15 typically result from assigning a peripheral to use it while forgetting to disable the integrated secondary IDE controller. Most Pentium or later (PCI-based) motherboards have two integrated IDE controllers. Some people incorrectly assume that there will be no conflict if nothing is attached to the secondary channel, but this is not always the case.
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by Awgeewhiz edited by dbmaven
last modified: 2003-09-05 11:02:47 | | | What is an 80 conductor cable?
The 80 conductor cable is a new type of cable for attaching ATA (IDE) disk drives to systems or controller cards. It has 80 wires in the ribbon cable. Older ATA cables always had 40 conductors (drive connectors have 39 pins, one is removed as a key).
How Does It Work?
Every other line of the 80 conductor cables is tied to ground inside the connector. This results in a much better signal quality as the crosstalk (signals from adjacent lines coupling into each other) and ground bounce are greatly reduced. The cable is backward compatible with all old ATA drives, other than 2.5" drives. The connectors still have 40 pin sockets. Ultra ATA/66/100 drives still have 40 pin connectors.
UltraATA/66/100
UltraATA/66/100 is the new data transfer rates. The 80 conductor cable is required to run at 66/100 Megabytes/s. The cable was designed for automatic detection. When using UltraATA/66/100 a system must check to see if an 80 conductor cable is installed. If one of the lines (PDIAG) is grounded then is an 80 conductor cable. If the line is not grounded then it is a 40 conductor cable. Systems should automatically switch to UltraATA/33 mode if they sense a 40 conductor cable.
Cable Select
All 80 conductor cables support the Cable Select feature. If you set the drive address (Master/Slave) jumper to Cable Select then the drive uses the cable to determine if it is Drive 0 or Drive 1. Drive 0 is always the drive on the other end of the cable (black connector) from the system. Drive 1 is the drive near the middle (gray connector) of the cable.
Odd/Even
Due to the fact that the connector manufacturing companies rarely agree on anything there are two types of 80 conductor connectors, odd and even. Some manufacturers run the ground lines down the even wires and some run them down the odd wires in the 80 conductor cable. This is a problem only for cable assemblers. If you mix the two types of connectors on the same cable it shorts all the lines together. Once the cable is assembled correctly there is no problem.
This is not a problem for drives or systems as they still have 40 pin connectors.
To Sum Up:
80 Conductor Ribbon Cable
Required for UltraATA/66/100 Speed
Improved Signal Quality
Ground on all even lines or all odd lines in the cable
40 Pin Sockets on Cable (Just like before)
40 Pin Connectors on Drive (Just like before)
Backward compatible with all 3.5" drives
Supports Automatic Cable Type Detection
Supports Cable Select
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by vkr edited by dbmaven
last modified: 2003-09-05 11:04:09 | | | Everything you need to know about USB
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by NightLinks edited by dbmaven
last modified: 2003-09-05 11:06:37 | | | DMA or Direct Memory Access is a method of transferring data between a device and memory without CPU involvement. This way is faster. Also, the CPU can do other computation in the mean-time.
There are 2 DMA controllers in a PC, each providing 4 channels. Since one channel is used to connect the master DMA controller to the slave DMA controller there are 4 8-bit and 3 16-bit available channels. One channel can be used by one hardware device only.
Also see This page at TechTarget.com
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by redxii edited by dbmaven
last modified: 2003-10-27 00:08:53 | | | (Please note I got this information from HowStuffWorks.com)
A single IDE interface can support two devices. Most motherboards come with dual IDE interfaces (primary and secondary) for up to four IDE devices. Because the controller is integrated with the drive, there is no overall controller to decide which device is currently communicating with the computer. This is not a problem as long as each device is on a separate interface, but adding support for a second drive on the same cable took some ingenuity.
To allow for two drives on the same cable, IDE uses a special configuration called master and slave. This configuration allows one drive's controller to tell the other drive when it can transfer data to or from the computer. What happens is the slave drive makes a request to the master drive, which checks to see if it is currently communicating with the computer. If the master drive is idle, it tells the slave drive to go ahead. If the master drive is communicating with the computer, it tells the slave drive to wait and then informs it when it can go ahead.
The computer determines if there is a second (slave) drive attached through the use of Pin 39 on the connector. Pin 39 carries a special signal, called Drive Active/Slave Present (DASP), that checks to see if a slave drive is present.
Although it will work in either position, it is recommended that the master drive is attached to the connector at the very end of the IDE ribbon cable. Then, a jumper on the back of the drive next to the IDE connector must be set in the correct position to identify the drive as the master drive. The slave drive must have either the master jumper removed or a special slave jumper set, depending on the drive. Also, the slave drive is attached to the connector near the middle of the IDE ribbon cable. Each drive's controller board looks at the jumper setting to determine whether it is a slave or a master. This tells them how to perform. Every drive is capable of being either slave or master when you receive it from the manufacturer. If only one drive is installed, it should always be the master drive.
Many drives feature an option called Cable Select (CS). With the correct type of IDE ribbon cable, these drives can be auto configured as master or slave. CS works like this: A jumper on each drive is set to the CS option. The cable itself is just like a normal IDE cable except for one difference -- Pin 28 only connects to the master drive connector. When your computer is powered up, the IDE interface sends a signal along the wire for Pin 28. Only the drive attached to the master connector receives the signal. That drive then configures itself as the master drive. Since the other drive received no signal, it defaults to slave mode.
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last modified: 2003-10-26 23:44:09 |
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