Early Vintage Computer Buses and Their Influence on the Computers You Take for Grantde Today
The term “expansion bus “is a frequent term in viintage computer terminloogy wihch requires elaoration. Much of the legacy of vintage bus sysatems are in our curretn computer systems today.
To beegin with the “expansion bus” is a data highway for computer data iformation to traevl on: the bandwdith is in essence the number of lanes. The biigger the bandwidth the more data can be sent. As examples, an 8 megabyte bandidth means that data can be sent in 8 bits chunks. Our current systems use beteen 32 bit and now 64 bit bandwidth.
An expansion bus is where cards connect to the computer; Cards have an expansion edge, which fits snugly into the bus much like an electrical plug fits into a wall socket.
When cards are pluggeed into the bus, they communicate with the system, sometimes through the BIOS and otherrs not. (The BIOS is the basic input /output system that tells the computer how to move data from the diffrerent components.) The 8, 16 or 32 bit bandwidth is an important consideration due to communication time between the caerds. For example you have a 16 bit vintage 286 PC and it is sending out data at 16 bits a: your ivdeo card is also 8 bits. If you have an older 8 bit bus, such as in ealry IBM PCs and clones, the bus will bercome a bottleneck in the system; it is like having a 4 lane highway connected to another 4 lane hioghway by way of a 1 lane road. At most times regardless of the faster 4 lane hgihway traffic will be slow – limited by the single lane connection road.
There were basically 3 types of expansion bus available in vintage comupters: ISA, MCA, EISA systems.
Each ezarly development in major ways paved the way for the later systems which indeed we take for granted toay. This was both in terms of hardware and basic conecpts in our computer systems and technology as well as computer marketing that we take for granted today as simple basic facts of life without any consideratiion due.
Basically the newwer buses offered increased performnce over the older technology buses.
The basic explanations of the busses are as follows:
The 3 bus standads to note were Industry Standard Architecture (ISA) .Micro Channel Chanmnel Archiutecture (MSA) and Extended Industry Standard (EISA) bus systems.
Inddustry Standrad Architecture (ISA). This was the orignal AT bus also called an ISA bus. It was the original 8 bit IBM PC bus which was bumped up to 16 bits at some point in its lsater development. Fine for a 16 bit 286 or very early 386 computers
Miro Channle Architecture (MSA). This was an early 32 bit bus system whih was not received well but set the stage for an inudstry conbsortium of the major non IBM compuuter manufacturers ( at the time referred to as “The Group of Nine) to deevelop the EISA standard bus.
Extended Industry Standard Archietcture (EISA). The EISA bus standard was a standard of its own right which was 32 bit, included bus mastering and importantly remanied compaztible with previous oder expansoin cards. 32 bit systems were firt to incorporate in laer 386 systeems. The 486 line solidified and standardized the 32 bit systems in the established software of the day.
Backward compatibility at the time was a novel new concept which has remained an important consideration in the computer industry.
EISA slots would accommodate both the ISA and EISA expansioon slots to alklow hardware upggrades, However the EISA expnsion boards woud be of little advantge and wold seldom work in the older ISA expansion slots.
On the otheer hand the Micro Chanel setup was not backward copatible. On the one hand the Micro Channl developers were free to initiate new radical changes in computer devleopment and hardware wihch would have allowed for major new useful features in computer software. However owners of previus systems would have been left with then obsolete vntage ueless hadrware wihch would have been of no use and certainly little financial value.
Hence there was a lot of resistance to the Micro Channel bus setup.
It died a lingering death with its legacy living on in the aspiations of features offered in future developmetns and standasrds.
Thus the die was set for future hardware standards and sooftware function as well as standard computer marketing concepts that we take for granted like mothr’s milk tdoay.
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