| ke a lot for granted in our modern Pentium 4 and | | | | be found in such peripherals as hard drives, sound |
| advanced Atahlon computers. Plug and play, | | | | and video cards. |
| instant hardware configuration for the | | | | The overall computer system may become much |
| motherboard and accessory cards are pretty | | | | more efficient if these in essence peripheral CPUs |
| standard stuff. | | | | can communicate directly with each other. without |
| However it was not always that way. Early | | | | having to use the main CPU as an intermediary. |
| motherboards were limited in terms of computing | | | | Hence MCA and EISA were developed with these |
| speed and had to be manually set up and | | | | roles in mind. The concept became known as |
| configured by tech experts with physical | | | | “bus mastering”. |
| “jumper settings:” among other | | | | Bus mastering involves the concept that the |
| skills. | | | | peripheral CPUS could request permission to take |
| These were not skills that knowledgeable | | | | over the bus for a short period of time. The main |
| teenager hackers generally had. If you wanted to | | | | CPU would grant permission for them to take |
| compute so to say just as you had to have a | | | | over the bus, and it would temporarily drop |
| good mechanic for your car you needed and | | | | “out of the loop”, enabling swift |
| excellent computer technician. | | | | communications between for example the hard |
| Things were humming along early on with the | | | | drive and floppy disk drive. |
| advent of 386 and 486 era computers. All in all | | | | As computer busses developed and had the |
| there were a number of ongoing improvements. | | | | inherent abilities to transfer more and more data |
| These included. 32 bit widths. Bus mastering. Less | | | | in a given time period noise became an issue. The |
| susceptible to noise in that they were | | | | ISA bus was fairly noise prone because it relied |
| “quieter’ in signal transmission. | | | | on triggered interrupts. Whenever the voltage |
| More convenience of setup of adds on boards via | | | | level on the data line of the bus exceeded a given |
| software. | | | | threshold value then “Edge |
| Just as all roads so to say lead from Rome early | | | | Triggering” would result. |
| computer advances all came from improvements | | | | The alternative to this situation where |
| in the “Computer Bus”. | | | | “Edge Triggering” could result is |
| The ISA bus came in only 8 bit and 16 bit | | | | “level triggering” where it is |
| formats. Whereas the later 386 and 486 chips , in | | | | required that the transmitting hold and archive the |
| both the DX and SX formats while they did have | | | | higher voltage level in order for data to be |
| a 32 bit path were hobbled by the ISA bus. As a | | | | recognized by the devices on the bus. Edge |
| result they could never realize their true 32 bit | | | | Triggering however can lead to |
| speed potential. Later buses such as the MCA and | | | | “transients” – that is brief |
| EISA busses were able to overcome these | | | | power surges that can confuse the devices on |
| inherent limitations. | | | | the bus into thinking that data is on the bus when |
| Thee “data highways” referred to | | | | it is not. Luckily level triggering lowers the noise |
| as “: busses” are the data | | | | level and both MCA and EISA employ it. |
| transmission lines around the PCs. The bus serves | | | | As a result of all of these inherent benefits MCA |
| as the path for information transmission around | | | | and EISA came to support the idea, which we |
| the PC. True this routing is controlled by the CPU. | | | | know take for granted, of instant software |
| However as that point in vintage computing | | | | configurations. There were no switches or |
| history this was not an issue. The PCs were stand | | | | jumpers on add in MCA or EISA boards. Although |
| alone single CPU units. | | | | we take plug and play instant configuration of |
| However as time went on and PCs got faster | | | | mother boards and peripherals such as sound, |
| and more complicated with less expensive | | | | video or network cards for granted it was not |
| additional CPUs handling other tasks within the PCs | | | | always that way. We owe a lot to these early |
| events became dicer. | | | | computer innovations of improving the computer |
| Onboard peripherals themselves began to have | | | | bus. |
| built in CPUs. CPUS in different manners began to | | | | |