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*!#$*&<at>* COMPUTERS Sorting out what’s really to blame If there’s one thing I’ve learnt about computers over the years, it’s not to jump to conclusions when something doesn’t work properly. When things go wrong, it’s all too easy to blame the obvious, without getting to grips with what’s really at fault. By GREG SWAIN How often have you heard that a par­ ticular operating system is unstable? Or that it doesn’t work on such and such a computer? Or that a particular item of hardware has a “bug” and should be avoided? Or that something just doesn’t work when your own ex­ perience indicates otherwise? When it comes to computers, there are enough real problems to sort out without having to also sift through a mine of misin­formation, straight-out even been told that PCs are no good in this role because “they just don’t work” and because “they have font problems”. Well, you could have fooled me. There we’ve been all those years, suc­ cessfully producing a magazine using PCs that don’t really work – at least according to the hearsay of several self-appointed experts. What rubbish! We’ve used PCs in the desktop publishing role for over “A computer is really a box full of grem­lins, just waiting to wreak all sorts of havoc at the user’s expense”. bad mouthing and old wives’ tales. I’d like a dollar for every time that someone has rolled their eyes to the ceiling when told that SILICON CHIP is produced using PCs, for example. I mean, everyone knows that Macs are the all the go when it comes to desktop publishing, don’t they? I’ve 4  Silicon Chip six years now with very few problems but try telling that to some people. Not that it’s ever really worth the bother – a few pointed questions in­ variably reveal that such people know very little about PCs, and are simply basing their opinions on “common knowledge”. It’s all the stuff of myths and legends but if it’s “common knowledge”, then it must be true. I’m not seeking to belit­ tle Macs here, by the way. I’m simply making the point that the PC is a valid alternative for desktop publishing, de­ spite what many ill-informed people will try to tell you. The most common misconceptions by far arise out of hardware and soft­ ware upgrades. The reasons are not too hard to find. Hardware upgrades, in particular, are often not straight­ forward for a variety of reasons. After several recent experiences of my own, I’m convinced that a computer is really a box full of grem­lins just wait­ ing to wreak all sorts of havoc at the poor user’s expense. OK, so I’m exaggerating somewhat but if you’ve ever at­tempted to add hardware to a PC, you’ll know what I mean. Even Windows 95’s much vaunted Plug and Play (PnP) system has problems in some circumstances. Let me give you a couple of examples of what can happen when even rela­ tively simple upgrades are attempt­ed. The not-so-crook RAM Recently, we decided to upgrade the RAM in a couple of our office machines from 32Mb to 64Mb. These two machines used iden­tical mother­ boards and in each case, the existing RAM consisted of two 16Mb SIMMs. As a result, we decided to purchase two new 32Mb SIMMs for the first machine and transfer its existing 16Mb SIMMs to the second machine. Installing the new 32Mb SIMMs was straightforward enough but when we We solved the problem by leaving the new SIMMs in the third machine and sharing its original four 16Mb 70ns SIMMs between the first two machines. So all three machines ended up with 64Mb of RAM – it’s just that the two new 32Mb SIMMs ended up in an unexpected location. But it’s easy to see how misun­ derstandings can arise in this sort of situation. We could have easily been fooled into returning perfectly good RAM to the supplier, demanding that it be replaced. And of course, the re­ placement RAM would have caused exactly the same problems. upgrades. Win95 cannot automati­ cally assign interrupts (IRQs) to nonPnP expansion cards (now referred to as “legacy” cards) and can easily get itself into a knot if left to its own devices. To explain, a standard PC has 16 interrupts (0-15) avail­able but most of these are taken by the system, leaving about six free for expansion cards (de­ pending on the configuration). Each expansion card must be as­signed a unique IRQ; if two cards have the same IRQ, there will be a conflict and the system won’t work properly. The “minimalist” approach usually works well when install­ ing Win95, particularly if you have a mixture of legacy and PnP cards. This involves removing all non-essential cards, such as sound cards and network cards, before installing the software. Once the system is up and running properly, you can add the expansion cards back in, one at a time. By the way, it’s best to add the legacy cards first, as the PnP cards are auto­ matically assigned the leftover IRQs. In addi­tion, the system assigns IRQs to PnP cards in ISA slots before those in PCI slots. Note also that you should reserve the appropriate IRQs for the legacy cards in the system BIOS, where this facility exists (ie, if the motherboard has a PnP BIOS). This will usually be found under a “Plug and Play Config­ uration” (or similar) menu. For exam­ ple, if you have a legacy card that’s set to IRQ10, then you must assign IRQ10 for use by an ISA card. The above step is quite important. If you don’t do it, Win95 may automat­ ically assign an IRQ that’s already in use to a PnP card. Operating system myths The suspect motherboard There are also plenty of myths floating around regarding operating systems. One that I’ve heard from a couple of people is that Windows 95 needs a Pentium processor and won’t run on a 486. Wrong! What they really mean is that they couldn’t get it to work on their particular 486 for some reason or other. To prove the point, we recently installed the Win95 upgrade pack on an old 50MHz 486 machine. It ran without a hitch and I’ve even heard of people running Win95 on a 386. Hardware conflicts are often the root cause of aborted operating system It’s not just hardware conflicts that can be a problem. Hardware bugs can also cause problems and lead to unfair criti­cism of an operating system or even individual programs. Consider my own experiences with Windows 95 which is in­stalled on my main office machine. This is one of the machines described above that didn’t like the 60ns 32Mb SIMMs and the problem I am about to describe is directly related to the memory upgrade. As mentioned earlier, this machine was originally config­ured with 32Mb of RAM (2 x 16Mb SIMMs). It is set up This new motherboard cured an unstable Windows 95 installation. The bus speed of the motherboard in the original machine had apparently been pushed beyond its design limitations – or, at least, that’s one theory. switched on, the machine refused to boot. Sometimes it would just hang after completing the BIOS checks. At other times, it would start to boot the operating system and then halt, with a screen full of obscure error messages. Our first thought was that we must have dislodged a cable when installing the new RAM but a quick check re­ vealed that all was as it should be. Our next snap diagnosis was crook RAM and this was seemingly confirmed when it also failed to work in the sec­ ond machine. Yet when we substituted the old RAM, both ma­chines booted without problems. That was it, of course – one of those new 32Mb SIMMs just had to be faulty! But was it? Perhaps the problem was in the two machines which, after all, were virtually identical. The only way to find out was to try the new SIMMs in a third machine with a completely different motherboard. When we did, it booted straight up and performed flawlessly. So much for our snap diagnosis of faulty RAM! Instead, it appears that the motherboards in the first two machines weren’t happy with the 60ns RAM on the new SIMMs (the older SIMMs used 70ns RAM). And there were no settings in the system BIOS that could compensate for this. February 1997  5 You can easily check for hardware conflicts in Win95 by double-clicking the “System” icon in “Control Panel”, then se­lecting the “Device Manager” tab. Doubleclicking on a specific device then gives you the “Resources” tab, which lets you view the resources allocated. as a dual-boot Windows 3.11/Win95 system but I was never entirely happy with the system under Windows 95 as it occasionally crashed when the going got heavy. My first inclination was to blame which ever program I happened to have running at the time but eventu­ ally I began to suspect Windows 95 itself. However, the pattern was too intermit­tent to really get to grips with the problem. The breakthrough came when 6  Silicon Chip the extra 32Mb of RAM was added. Windows 3.11 continued to work nor­mally but not so Windows 95. It now frequently crashed, generat­ ing “Unexpected Exception” errors in the process. And when it crashed, it would often refuse to boot again unless the addition­al RAM was removed. This meant that the problem was probably hardware related. Initially, I simply tried replacing the original RAM with the second two 16Mb SIMMs but this made no difference. I also tried swapping memory banks and substituting the memory from the machi­ne’s twin without result. By now, the finger of suspicion was pointing fairly and squarely at the motherboard. After all, it had previ­ ously failed to work with the 32Mb SIMMs, so it was definitely suspect when it came to handling mem­ory. And there was another thing. The machine ran a 133MHz Pentium processor but the manual that came with the motherboard only mentioned 75MHz and 90MHz processors. An 8-way DIP switch is used to set the bus and processor clock speeds but the manual gave no details of the settings. Fortunately, the settings were screen-printed on the moth­ erboard in a vacant area adjacent to the micro­ processor. But what was interesting was that the machine’s twin, which was purchased four months later, also showed an additional setting for a 100MHz processor. And both ma­ chines were set to this configuration. That aside, the motherboard was obviously originally de­signed to op­ erate at a bus speed of either 60MHz when used with a 90MHz processor, or 50MHz when used with a 75MHz (or 100MHz) processor. That’s because the processor always runs at some ratio of the bus frequency, the available ratios in this case being 1.5x and 2x (ie, 1.5 x 50MHz = 75MHz, 1.5 x 60 = 90MHz, and 2 x 50MHz = 100MHz). So what was going on? A 133MHz processor requires a 66MHz bus so the board must have been tweaked to run at this higher speed – probably by the simple expedient of substituting a different crystal in the clock circuit during manufacture. Fairly obvious­ly, this was an existing design that had been hastily adapted to cater for the faster processor but it appeared that it wasn’t up to the task – at least not with Windows 95. There was nothing for it but to change the board. It ain’t that easy Now if you thought that changing the motherboard in a Win95 system was a straightforward task, think again. The mechanical installation is easy enough but getting everything up and running again is a different matter. Windows 3.11 was OK (it’s too dumb to recognise the swap) but Windows 95 is too clever by halves, tying itself in all sorts of knots when it discovered SILICON CHIP SOFTWARE Now available: the complete index to all SILICON CHIP articles since the first issue in November 1987. The Floppy Index comes with a handy file viewer that lets you look at the index line by line or page by page for quick browsing, or you can use the search function. All commands are listed on the screen, so you’ll always know what to do next. Notes & Errata also now available: this file lets you quickly check out the Notes & Errata (if any) for all articles published in SILICON CHIP. Not an index but a complete copy of all Notes & Errata text (diagrams not included). The file viewer is included in the price, so that you can quickly locate the item of interest. The Floppy Index and Notes & Errata files are supplied in ASCII format on a 3.5-inch or 5.25-inch floppy disc to suit PC-compatible computers. Note: the File Viewer requires MSDOS 3.3 or above. ORDER FORM PRICE ❏ Floppy Index (incl. file viewer): $A7 ❏ Notes & Errata (incl. file viewer): $A7 ❏ Alphanumeric LCD Demo Board Software (May 1993): $A7 ❏ Stepper Motor Controller Software (January 1994): $A7 ❏ Gamesbvm.bas /obj /exe (Nicad Battery Monitor, June 1994): $A7 ❏ Diskinfo.exe (Identifies IDE Hard Disc Parameters, August 1995): $A7 ❏ Computer Controlled Power Supply Software (Jan/Feb. 1997): $A7 ❏ Spacewri.exe & Spacewri.bas (for Spacewriter, May 1997): $A7 ❏ I/O Card (July 1997) + Stepper Motor Software (1997 series): $A7 POSTAGE & PACKING: Aust. & NZ add $A3 per order; elsewhere $A5 Disc size required:    ❏ 3.5-inch disc   ❏ 5.25-inch disc TOTAL $A Enclosed is my cheque/money order for $­A__________ or please debit my Bankcard   ❏ Visa Card   ❏ MasterCard ❏ Card No. Signature­­­­­­­­­­­­_______________________________ Card expiry date______/______ Name ___________________________________________________________ PLEASE PRINT Street ___________________________________________________________ Suburb/town ________________________________ Postcode______________ Send your order to: SILICON CHIP, PO Box 139, Collaroy, NSW 2097; or fax your order to (02) 9979 6503; or ring (02) 9979 5644 and quote your credit card number (Bankcard, Visa Card or MasterCard). ✂ the new motherboard. This problem apparently stems from the fact that the param­eters of the new motherboard and its BIOS don’t match the exist­ing registry settings. In the end, the only way around the prob­lem was to clean off the existing installa­ tion and its associated applications and reinstall all software. If you’re ever in this situation, by the way, don’t be tempted to simply reinstall the operating system over the top of the existing installation. It’s best to clean everything off and go for a fresh installation. The Win95 reinstallation was not without a small glitch, however. I’d removed the sound card but left in a SCSI card and a PnP network card. Everything went fine until the first boot. Windows 95 made it past the logon dialogs but then announced that it was searching for new hardware. There followed a brief period of hard disc activity, after which it just “hung”. I tried switching the machine on and off several times but always with the same result. Eventually, I pulled the network card and tried again. And that was it – the system now booted correctly and I was able to reintroduce the sound and network cards. Windows 95 now recognised the network card, installed the correct driver for it and automatically as­ signed an available IRQ. Now why didn’t it do that in the first place? Did the new motherboard do the trick? Well, based on my limited obser­ vations so far, the answer is yes. I now have a stable Windows 95 installation but just think how easy it would have been to jump to con­clusions and badmouth the operating system. Strangely enough, the other ma­ chine with the identical motherboard operates perfectly with its 64Mb of RAM but then it’s running Windows NT. So is Windows 95 fussier than NT about the hardware company it keeps? Or was it just a matter of manufac­ turing tolerances between the two boards? Or was the problem caused by some subtle hardware conflict which is now resolved and nothing to do with the motherboard at all? Finally, could I have cured the prob­ lem by changing the DIP switches so that the motherboard ran at a slower bus speed (yes, this would have throt­ tled back the processor)? We’ll probably never know the an­ SC swers to those questions. February 1997  7