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COMPUTERS Troubleshooting Your PC; Pt.2 Installing a new card into your PC can be a satisfying experience and can save you money – provided you know what you are doing. Here’s how to avoid the problems and keep your sanity. By BOB DYBALL Have you been thinking of installing an internal modem only to have a friend advise you to buy an external unit instead, because an internal unit is hard to get working? Getting an internal modem or some other add-on card going can be a frustrat­ing experience but it needn’t be if you follow a few simple rules. In this article, we’ll take a look at how add-on computer cards are installed under DOS, Windows 3.x and Windows 95. Due to the similarities to Windows 95, users of both Windows 98 and Windows NT 4 should also 4  Silicon Chip find this information useful. If you plan on installing a new card, or are already having problems with one, you must approach the job in a logical manner. In particular, it is important to avoid “resource conflicts” with other cards or peripherals. In fact, resource conflicts with other hardware items are one of the most common reasons for a new card not working. Fortunately, there are only a few simple rules to learn and by applying these, it’s likely that your new card will work first time. But first, here’s some background on how your PC handles plug-in cards and what fits where. IRQ, DMA, huh what? Computers collect new words and jargon like a dog collects fleas. You don’t need to be a rocket scientist to get a new add-on card going but you do need to understand some of this jargon. We’ll begin with the “system resources”. The term “system resources” covers a number or resources in your computer, including Interrupt Requests (IRQs), Direct Memory Access (DMA) channels, Input/Output (I/O) Ports and Memory. In general, no two devices can share the same resources; if they do, then either one or both devices will refuse to work. Let’s take a look at this in greater detail. Interrupt Requests: an IRQ or “interrupt request” is usually one of the most important things you need to consider when installing an add-on card into your PC. An IRQ is necessary for the add-on card to gain the attention of the computer. Basically, it inter­rupts it, as the name suggests. For example, a serial mouse is usually connected to serial port COM1 which is normally on IRQ4. Now if the PC were to con­tinually check the serial port for mouse movement, it would waste a lot of time that could be better spent on other tasks. Instead, moving the mouse sends data to the serial port and this in turn generates an “interrupt” signal to tell the CPU to process this new data (when it gets around to it). When the interrupt is processed, the “buffer” (a small memory holding area) is emptied of the mouse data and the computer carries on as before. Usually, the same IRQ is not shared between devices; ie, a device using say IRQ4 will normally expect to be the only device on IRQ4 and may even cease working if it isn’t. There are a couple of exceptions to this rule but these can vary somewhat from one machine to another. For example, although IRQ7 is normally assigned to parallel port LPT1, it can also sometimes be shared with say a sound card or an extra serial port. Usually, this works fine if the parallel port mode is set is SPP (Standard Parallel Port) but it might not work if the parallel port is set to EPP (Enhanced Parallel Port) mode and won’t work at all for ECP (Enhanced Communications Port) mode. In all, your computer has 16 possible IRQs, most of which are already reserved for basic system functions and hardware. Table 1 shows a list of common IRQ assignments, including those IRQs that are free for use with expansion cards. Direct Memory Access (DMA): this resource allows data to be moved between memory and other devices in your system. The DMA con­troller chip receives information on the data to be sent and its location, and allows the CPU to do more useful tasks than repeti­ tive data transfers. Most machines have seven DMA channels and these are usually labelled as DMA 1, DMA 2, DMA 3 and so on. Although DMA channels can sometimes be shared, depending on the hardware and software drivers involved, this is best avoided if possible. Input/Output (I/O) Ports: these Table 1: Standard IRQs IRQ 0 Function System timer 1 Keyboard 2 Cascade from IRQ9; often free to use 3 Serial port COM2 4 Serial port COM1 5 Reserved for printer port LPT2 (if present); commonly used by sound card 6 8 Floppy disc controller Printer port LPT1. If port mode set to SPP, can often be shared with serial port, internal modem or sound card Real time clock 9 VGA card. Often not needed by VGA card and may be free to use 10 May be free to use 11 May be free to use 12 Used by PS/2 mouse in some PCs; may be free to use 13 Co-processor 14 Primary IDE hard disc controller 15 Secondary IDE hard disc controller; usually free in 486 and earlier PC. 7 Note: additional cards should only be set to those IRQs that may be free to use allow the CPU to communicate with other devices (eg, serial and parallel ports, expansion cards, keyboard, etc). I/O ports are given an address in hexadecimal format or “hex” (base 16); eg, 3C0H or 200-20FH can be assigned to an I/O port. I/O ports are not shared. This means that each device must have its own I/O port or range of ports. Random Access Memory (RAM): RAM is where information is temporar­ily stored in your PC and is accessed by referring to its “ad­dress” (every memory location is numbered). Memory address “ranges” (limits) have changed over the years, with newer CPUs allowing more memory to be addressed. The 8088 and 8086 CPUs, for example, could only address 1Mb (1024 x 1024 or 1,048,576 bytes) of RAM, while the 80286-based PC/AT could address 16Mb. Note that the 1Mb and 16Mb limits are re­ferred to as “address space” and don’t mean that you can have 1Mb or 16Mb of free RAM at your disposal. That’s because special areas of memory are allocated to special tasks. Memory addresses cannot be shared with other devices. There would be little point in retrieving information from two differ­ent places with the same address if we don’t know which is cor­rect. OK, with that under our belts, let’s find out how to go about installing expansion cards without causing resource conflicts. We’ll start with the non-PnP (Plug and Play) cards. Legacy cards Although most new cards sold today will be Plug and Play (PnP), there are still a few that aren’t. And, of course, there are still lots of older cards in use, which means that you may have to mix PnP and non-PnP cards in the same machine. If you have a non-PnP card (usually referred to as a “lega­cy” card), you will have to manually set the card so that it uses the available resources, as required. This involves either set­ting hardware jumpers (or DIP switches) on the card or configur­ing the card using the supplied software (or sometimes both). (1). Jumpers are small plastic covered links that are used to short two pins together. Often, you will have to set several such jumpers to hardware configure a legacy card, as described in the manual. The idea here is to allocate “free resources” to the card, to avoid conflicts with existing devices. A system with one or more legacy cards can be difficult to configure if you don’t have the manuals. Each June 1998  5 card designates software control or hardware-jumpered control. Troubleshooting legacy cards Fig.1: Microsoft Diagnostic (MSD) is useful for showing which IRQs might be free to use but note that it may not be 100% accurate. Nor will it show which IRQs have been assigned to any expansion cards that have been added. card needs to be removed, reset and replaced to alter the system resources it uses. However, if a card’s manual has been lost, you won’t know what the jumper settings mean unless a diagram has been silk-screened onto the PC board. The moral here is simple – don’t lose the manuals as you will probably need them again one day. (2). Software configuration allows you to set the card up by running a special utility program. This may be supplied on a floppy disc or on a CD-ROM, or on some other media. Typically, the configuration utility 8-Bit Card will install a special device driver into config.sys or autoexec.bat. This will typically set the resources used by the card at boot up, or may be used to enable and disable various features on the card. The main advantage of software configuration is that you don’t need to remove the card from the mother­ board to change its settings. This means that you can quickly change the settings and try again if you run into problems. (3). Some legacy cards provide both hardware and software configuration. Usually, a jumper position on the 8-Bit Slot Jumpers For Setting IRQs, etc 16-Bit Slot 16-Bit Card The differences between the 8-bit and the wider 16-bit slots and cards is clearly shown in this photograph. A 16-bit card will give you more IRQs to choose from. 6  Silicon Chip (1) Conflicts with other software configured cards: soft­ware control methods for legacy cards vary, as there is no common standard system. Interactions between cards or between a card and the motherboard are not unusual. If you find a card does not respond to the configuration utility, try to configure the card with as few other cards in the PC as possible. Alternatively, try configuring it in a different PC first to reset it. (2) IRQ Conflicts: as mentioned before, shared IRQs should be avoided. If you are short of IRQs, try IRQ 7 after changing the printer port mode to SPP. Alternatively, try IRQ 2 (9) if this hasn’t been used by the VGA card. Don’t be fooled into thinking that a device that’s not currently in use has its assigned IRQ free. For example, if you have nothing connected to COM1 (IRQ 4) and say a mouse on COM2 (IRQ 3), then IRQ 4 is not free to use on COM3. IRQ sharing problems will still appear sooner or later due to the “default interrupt handler” on IRQ 4 for COM1. In other words, don’t be tempted to try setting your new internal modem or extra serial port to COM3 IRQ 4. If you do, it won’t work. COM 1 is already assigned IRQ4 and won’t like having it shared. Instead, you will need to assign COM3 a different free IRQ, such as 2, 5, 7, 9, 10, etc. So how do you know which IRQs are free? Well, you could try using a diagnostic utility such as Microsoft Diagnostic (MSD) or Norton Utilities. The MSD utility is supplied with MS-DOS and most versions of Windows. DOS and Windows 3.x users should look in c:\dos or c:\windows directory for msd.exe. Most releases of Windows 95 also include msd.exe, though you need go to the \other\msd folder on the Windows 95 CD to find it. Don’t assume that the list of IRQs given by a diagnostic utility such as Norton Utilities or Microsoft Diagnostic (MSD) is 100% accurate. These programs guess at what is being used and the guess is based on standard IRQs, like those in Table 1. If MSD or Norton Utilities knew everything, there wouldn’t be any need for Plug and Play! A quick look through config.sys and Fig.4: double clicking on Computer in the System Properties dialog box brings up a list of the IRQs used by the computer and the devices using them. Fig.2: this window is accessed by double clicking the System icon in Control Panel, then clicking the Device Manager tab. It presents you with a list of everything in your computer – as far as your computer is concerned. Double clicking on any item with a “+” symbol reveals the individual devices being controlled. A yellow exclamation mark next to a device indicates a resource conflict. Fig.5: this dialog box shows the I/O address used by the various devices in the PC. Fig.3: selecting a device and then clicking the Properties button and the Resources tab brings up this dialog box. It shows the resources used by the particular device (in this case, a sound card) and also indicates any conflicting devices (none in this case). Fig.6: you can also view the DMA channel assignments. Note that any DMA channel used by legacy cards should be reserved in the system BIOS. June 1998  7 ROM PCI/ISA BIOS (PI55T2P4) PNP AND PCI SETUP AWARD SOFTWARE, INC. Slot1 (RIGHT) IRQ Slot 2 IRQ Slot 3 IRQ Slot 4 (LEFT) IRQ PCI Latency Timer : : : : : Auto Auto Auto Auto 32 PCI Clock DMA 1 Used By ISA : Yes DMA 3 Used By ISA : No/ICU DMA 5 Used By ISA : No/ICU IRQ    3 IRQ    4 IRQ    5 IRQ    7 IRQ    9 IRQ 10 IRQ 11 IRQ 12 IRQ 14 IRQ 15 : : : : : : : : : : No/ICU No/ICU Yes No/ICU No/ICU Yes No/ICU No/ICU No/ICU No/ICU NCR SCSI BIOS USB function Used By ISA Used By ISA Used By ISA Used By ISA Used By ISA Used By ISA Used By ISA Used By ISA Used By ISA Used By ISA ISA MEM Block BASE : No/ICU : AUTO : Disabled ESC : Quit ↑ ↓ → ← : Select Item F1 : Help PU/PD/+/- : Modify F5 : Old Values (Shift)F2 : Color F6 : Load BIOS Defaults F7 : Load BIOS Defaults Fig.7: if you install a non-PnP (legacy) card in your PC, then you must reserve its IRQ assignment in the system BIOS in order to ensure that PnP cards will function correctly. Here, IRQs 5 and 10 have been reserved for legacy cards. autoexec.bat will often tell you what’s free and what’s not. If you cannot recall what a scanner card or a sound card is set to for example, look for the relevant entry in these two files. Often, it will contain someth­ing like /In or /I:n, where n is the IRQ that the card has been set to use. Typing SET at the command prompt will also usually provide the BLASTER environment variable. This line will include In, where n is the IRQ that the sound card is using. Still short of IRQs? If your card is an 8-bit card, check to see if you can obtain a 16-bit card instead (this will offer more IRQs to choose from) or, even better, one that doesn’t require an IRQ setting but can use other re­ sources instead. Check your VGA card as well. Some VGA cards have a jumper to disable IRQ use and this will free up IRQ 9 (IRQ 2). If you have a 16-bit sound card on IRQ 5 and find that IRQ 5 is all you can set your new add-on card to, try changing the sound card to IRQ 7 or IRQ 10 to free up IRQ 5. Although a few older DOS games won’t work on IRQ 10, most games will work fine on IRQ 7 or IRQ 10. What is Plug and Play? Plug and Play is a standard for automatically recognising and configuring 8  Silicon Chip just about everything you may wish to add to your PC (either externally or internally). In use since 1994, “Plug and Play” is often abbreviated to “Plug ‘n Play” or simply “PnP”. PnP standards have been applied to many newer ISA cards, PCI cards and mother­boards, as well as to monitors, joysticks, print­ers, modems and many other devices. The detection system used varies to fit the type of device. For example, video monitors use a serial E2ROM chip that contains all the details of the monitor (its refresh rates and so on). PnP modem detection, on the other hand, relies on the PC sending the modem a range of ATI commands (ATI0, ATI1 and so on) and using the responses it gets to determine the model. PnP cards are automatically detected by the PnP BIOS on your motherboard. The card is then assigned the resources it needs and the operating system kept informed of the cards found in the system and their settings. So why do some people call it Plug ’n Pray? There are a several reasons for this, although none are really the fault of the Plug and Play: (1). The user has a motherboard with a PnP BIOS, a PnP operating system (eg, Windows 95) and one or more older non-PnP cards. With this mix, it’s all too easy to get conflicts between non-PnP (legacy) and PnP cards unless you follow a few simple rules. Basically, you have to “tell” the system about any IRQs that have been assigned to the legacy cards. You do that by using the PnP motherboard’s BIOS to reserve the legacy card IRQs, so that they cannot later be assigned to PnP cards (and thus cause conflicts). This must be done for everything to work reliably, other­wise you may as well “Plug and Pray”. To use PnP correctly, you must remember how it works. By reserving the legacy card IRQs in the system BIOS, you let the operating system know which IRQs have already been assigned (by you manually), thereby leaving it free to assign the remaining IRQs to the PnP cards itself. If you do that, Plug and Play will generally work and work well! This process of locking out IRQs can appear in one of two ways. In some PCs, the BIOS will list all IRQs from 0-15 and will allow you to toggle between PnP or Legacy for each IRQ – see Fig.7. Let’s say, for example, that you are installing a legacy modem on COM3 IRQ 9. In that case, you would toggle IRQ 9 in the list to Legacy, press Escape, F10 and Y to save the settings to CMOS – and that’s it. The other common method of locking out an IRQ is via a list of four or so available IRQs – ie, 1st available, 2nd available, 3rd available and so on. Often, the default is 5, 7, 9 & 10. So if your modem is set to IRQ 9, then you would need to change 3rd available to 10 and 4th available to N/A. If you have to use a legacy card in an otherwise PnP sys­tem, make sure (after you lock out its IRQ in the system BIOS) that you set up the device in Windows 95 using the Add New Hardware wizard (in Control Panel). This done, double-click the System icon in Control Panel, click the Device Manager tab, click the new device and then click the Properties button. You should now confirm that the Automatic settings box is unchecked and that the I/O port, IRQ and other resources used by the card are set correctly. Change the resource allocations so that they agree with the settings on the card if necessary. Sometimes, however, the system won’t let you make any changes. If that happens, the Bus Slots For Those Who Missed The Bus Bus slots allow expansion cards to be plugged into a PC mother­ board. Although some mother­ boards have a proprietary bus or no provision for expansion at all (to reduce the physical size of the unit), most have one or more of the following standard bus systems: (1). 8-bit ISA slots: released in 1981, the original IBM PC, featured an 8-bit bus. This ran at the (then) blindingly fast speed of 4.77MHz and later became known as the ISA (Industry Standard Architec­ ture) bus. Early models of the PC had a separate fixed IRQ allocated to each slot. This meant that a card set to IRQ 7, for example, had to go into the last slot (the IRQs were numbered 0-7). This was soon changed to allow any of the IRQs to be available at each slot. (2). 16-bit ISA slots: in 1984, when the 80286-based PC/AT was introduced, the ISA slot grew from 8 to 16 bits, the number of IRQs increased to 16 (0-15), and the bus speed increased from 4.77MHz to 8MHz. 16-bit ISA slots are backwards compatible; ie, a 16-bit slot can accept an 8-bit card, with one section of the slot simply left unused. trick is to change the “Setting based on” option from “Basic configuration 0” to some other setting (eg, “Basic configuration 5”) and then try again. You may have to try several settings before you find one that will let you make changes. Usually, the first one or two “basic settings” are preset and cannot be changed. (2). The user has an old non-PnP motherboard and wishes to add new PnP expansion cards. Older mother­ boards with BIOS dates before 1994 or so won’t have PnP BIOS extensions. This means that you won’t be able to reserve IRQs for legacy cards in the system BIOS, because there is simply no provision to do so. The way around this is to configure any PnP cards in these older PCs as if they were “software configured cards”. Usually, there will be a DOS (3). MCA or Micro-Channel Architecture: introduced in 1987 by IBM, MCA had no backward compatibility but featured a 32-bit data bus, a 10MHz clock and auto-configuration of cards. Although technically brilliant, it flopped. IBM made MCA proprietary, thereby forcing prices up, choices down and users off to EISA bus or VLB bus instead. (4). EISA bus: the EISA bus was in­ troduced by Compaq to compete with MCA. Though not widely accepted by home users, it did have a following in the server market. It featured a 32bit data bus, a clock speed of 8MHz, bus mastering, auto-configura­tion of cards and backwards compatibility with ISA. EISA systems tended to be expensive. The add-on cards were also expensive and are now about as rare as MCA cards. (5). VESA Local Bus, or VLB: the Video Electronics Stan­dards Associ­ ation (VESA) introduced the VLB in 1992. It provided two or three slots with a 32-bit data bus directly con­ nected to the CPU. It was clocked at the same speed as the CPU, usually 25MHz, 33MHz or 40MHz. Although bus mastering and automat­ ic con­ figuration weren’t supported, it was backwards compatible with 8-bit and 16 bit ISA bus slots. PnP manager or software setup utility sup­plied, so that you can configure the card manually. Sometimes, problems can arise with older motherboards that have early PnP BIOS extensions. An update to the ROM BIOS can usually correct this. This will require a visit to your supplier (provided they can do the job), or you might try Mr BIOS on www.mrbios.com for a third party update. (3). The user has a motherboard with a PnP BIOS and is using PnP expansion cards but is still running DOS and Windows 3.x. Neither DOS nor Windows 3.x support PnP (unlike Windows 95, Windows 98 and, to some extent, Windows NT 4). If you need to keep using your older nonPnP operating system, you will need to use the DOS PnP manager supplied The VESA bus was popular in 486-based computers for video and hard disc controller cards, being ef­ fective in reducing data bottlenecks in the system. (6). PCI - Peripheral Component Interconnect: this was de­signed after Intel and others got together in 1991 and offers automatic configuration (PnP) and high-speed operation. PCI first appeared in some late-model 486 machines and is still the stan­dard bus used in nearly all PCs today. 64 bits of data are pushed through a 32-bit bus which is clocked at 33MHz. PCI can also pump data in burst mode to 133MHz, with newer versions offering even more. (7). Universal Serial Bus, or USB: although it’s still too soon for wide choices and low prices, USB is set to make quite an impact on the market. With transfer rates up to 12Mb/s, up to 127 USB devices can be daisy chained together and “hot swapped” (no need to turn the PC off first), all with Plug and Play recogni­tion. A large number of companies are getting into USB, with a whole host of new devices set to come onto the market. USB re­ quires at least Windows 95b (version 4.00950B or later) and a recent motherboard with USB support. with the card and treat any PnP cards in your system as if they were plain software-configured cards. In order for Plug and Play to work, it needs to be all or nothing; ie, you must have a PnP BIOS and a PnP operating system. (4). PnP motherboard BIOS, expansion cards all PnP, PnP operating system. This is my favourite – you simply plug in the cards and turn it on. And that’s pretty well all there is to it! If you are adding a PnP modem, for example, you let the auto-detection kick in, then insert the modem “driver” disc when instructed and the PnP system does the rest. You don’t have to worry about setting or reserving IRQs. Next month, we’ll take a look at some common modem problems and SC tell you how to fix them. June 1998  9