A BIOS primer

Windows Middle East's man in the know, Phil Croucher, goes about dispelling some common myths...

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By  Matthew Wade Published  April 2, 2006

|~||~||~|The systems that transform a PC from a group of component bits into a useful machine can be broken down into three groups, starting with application programs (such as word processors and spreadsheets), which are loaded up by an operating system (such as Windows or Linux), which before that is brought into being by your system’s BIOS (the Basic Input/Output System). BIOS beginnings In short, the BIOS consists of a collection of assembly language routines, which live in a chip on the motherboard and allow programs and your PC’s components to communicate with each other at a base level. Thus the BIOS works in two directions at once and is active all the time your computer is switched on. As a result, software doesn’t have to talk to a device directly, but it can call up a BIOS routine instead, which saves programmers writing the same stuff all over again (and also ensures that the code is consistent). However, the BIOS is still 16-bit code, which means that your PC starts off as what’s called a ‘PC XT’ when it is switched on, at least until an operating system such as Windows takes over. At this point, memory above 1Mbyte cannot be recognised, therefore because expansion cards need ROMs on them to be recognised at boot-up time and this is in fact quite an achilles heel (it can produce many incompatibilities as proven by the many updates that keep appearing), these days it is now bypassed by Windows. In fact, to dig deeper, ever since Windows NT came out the BIOS Code has been replaced with its own Hardware Abstraction Layer (HAL). There are now moves afoot to replace this on the motherboard with an Extensible Firmware Interface, or EFI, but that’s the subject of another article. The hobby of playing with the settings in the BIOS started way back in the early days, when programmers accidentally left such BIOS options available to PC engineers and designers, and accessible to the public through set-up screens. (In reality, these settings have nothing to do with the BIOS, but rather the chipset instead; they just happen to live in the same chip as the BIOS code, which leaves a little memory space available for them.) The chipset is really what manages access to system resou-rces such as memory, cache and the data buses, and allows data to be sent around the system in a smooth manner. Linking I.T. up The PC has never been designed as an overall entity - rather, individual parts have been designed by different companies and committees and made to fit together via a series of workarounds. If you wanted to play around with the inner workings, the priority was to ensure that the individual parts ran at compatible speeds - for example, if the PCI bus ran at 33MHz, the other parts would have to run at multiples of that to ensure that there was synchronisation. Otherwise, when data needed to be sent it would sometimes have to skip a beat until it could catch up with the rest of the machine. There has been some improvement over the years in terms of this aspect of performance, but with the underground hobby of overclocking, it is now more important than ever before to ensure items run in a stable fashion before you even think of trying to get them to work together. Next month I’ll outline the settings you should tweak before overclocking.||**||

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