The life and times of the modern motherboard

Posted at: Tuesday 27th November 2007 by Alex Watson

Ever wondered how a motherboard and its BIOS are designed and made? What makes one a brilliant overclocker and another as stable as a plate of jelly on a bouncy castle? Alex Watson investigates.

While the process of designing a motherboard might start with small frustrations such as wobbly PCI-E cards, the end result is a hugely complex piece of technology: a six, or even eight-layer printed circuitboard, 305mm x 269mm, with around 40 or so chips speckling its surface, all linked byhundred of twisting traces. How today's boards are designed is a fascinating story, and equally interesting is how they came to be the complex, copper-adorned products we know, love and overclock.

A brief history of motherboards

The first home computer to feature something close in spirit to a modern motherboard was the Altair 8800, which was released in 1975. The Altair was a kit PC, so buyers had to plug cards into slots to get the machine up and running - the first time expansion slots had been seen in a home PC. However, all the Altair's key components, such as the CPU (an 8-bit model from Intel) and the memory, were mounted on the cards. This meant that the motherboard had far more in common, design-wise, with the 'backplanes' of traditional, room-sized industrial computers. It was just a series of relatively dumb electrical interconnects.

The Altair might have been the first motherboard to have slots, but the Apple II made a bigger contribution towards shaping the development of the modern PC motherboard, pushing it towards being a flexible, expandable and sophisticated piece of technology in its own right.

While today's Apple products are fawned over and made fun of in equal measure for their devotion to exterior appeal, the Apple II backed its good looks with remarkably open hardware architecture. Beneath its beige plastic lid was a motherboard with expandable RAM - the base model had 4KB, but wealthier enthusiasts could expand this to 48KB - and eight free expansion card slots. These were proprietary to the Apple II, but the comprehensive manual that accompanied the machine, the 'Apple II Reference Manual' (which you can see on the web at www.apple-iigs.info/doc/docii.htm) laid bare how the hardware worked and how the system communicated with it. This meant that it was relatively easy for people to tinker with the Apple II's hardware and to produce their own expansion cards.

The commercial success of the Apple II and other early home computers, such as the Tandy TRS-80, convinced industry giant IBM that it too should make its own personal computer. By 1980, IBM had certainly tried, but the product it had launched - the 5100 - ended up as an also-ran. To beat Apple and Tandy, IBM needed to adopt a different approach. It created a special, autonomous team of 13 engineers to create a brand-new home PC. To get the product ready quickly, and avoid the delays and politically influenced decisions that caused problems previously, the team elected to use off-the-shelf parts to build their machine. The CPU came from Intel, while one of the three operating systems available at the start was supplied by a young, up-and-coming company called Microsoft. One of the few components IBM developed for the machine was the BIOS.