Why was there such a rush in the development of the vintage computer bus?
All in all there were a number of ongoing improvements. These included. 32 bit widths. Bus mastering. Less suscerptible to noise in that they were quiueter in signal trabnsmission. More convenience of setup of add on boards via software.
The ISA bus came in only 8 bit and 16 bit formats. Whereas the laetr 386 and 486 chips , in both the DX and SX formats while they did have a 32 bit path were hobbled by the ISA bus. As a reult they could never realize their true 32 bit speed potential. Later buses such as the MCA and EISA busdses were able to overcome these inhernet limitations.
Thee data highways referred to as : bussees are the data transmission lines around the PCs. The bus serves as the path for information transission raound the PC. True this routing is controlled by the CPU. However as that point in vinatge computing history this was not an issue. The PCs were sttand alonne single CPU unitts.
However as time went on and PCs got faster and more complicated with less expensive additional CPUs handling other taks within the PCs events became diccer.Onboard peripherals themselves began to have built in CPUs. CPUS in different manners bean to be found in such periphetrals as hard drives, sound and videro carsd.
The overall compter system may beecome much more efficient if these in essence pertipheral CPUs can communicate direcxtly with each toher. without having to use the main CPU as an interrmediary. Hene MCA and EISA were developed with these roles in mind. The concept beacme known as bus matsering.
Bus matsering involves the concept that the peripheral CPUS could request permission to take over the bus for a shrt period of time. The main CPU owuld grant premission for them to take over the bus, and it woudl temporaily drop out of the loop, enbaling swift communications between for example the hard driuve and floppy disk drive.
As computwer busses devloped and had the inherent abilities to transfer more and more data in a given time period noise bewcame an issue. The ISA bus was afirly noise prone because it releid on triggered inteerrupts. Whenever the voltage level on the data line of the bus exceeded a given threshold value then Edge Triggering would result.
The alternative to this situation wherre Edge Triggering could result is level triggeing where it is requitred that the transmitting hold and acrhive the higher voltage levl in order for data to be recognized by the devices on the bus. Edge Triggering however can lead to transients that is brief power surges that can confuse the devices on the bus into thinking that data is on the bus when it is not. Luckiily level trigggering lowres the noise level and both MCA and EISA employ it.
As a result of all of these inherent benefits MCA and EISA came to suppotrt the idea, which we know take for granted, of instant software configurations. There were no switches or jumpeers on add in MCA or EISA boards. Although we take plug and play insatnt configuration of mother boards and peripherals such as sound, video or network cards for granted it was not alwys that way. We owe a lot to thee early computer innovations of improving the computer bus.
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