In computers, PC / AT, using microprocessor i80286, became the first
apply the new system bus ISA (Industry Standard Architecture), fully
seize opportunities of the microprocessor. She characterized the presence of
an additional 36-contact connector for the card expansion. For
This target number of lines was increased by four, and data - at
eight. Now you can pass it along for 16 bits of data, and
through 24 address lines directly to 16 MB of system memory.
The number of lines of hardware interrupts in the tire has been increased from 7 to 15 and
channel DMA - from 4 to 7. It should be noted that the new system ISA bus entirely
included the possibility of an old 8-bit bus, that is, all devices,
used in PC / XT, could easily be applied in the PC / AT 286. System
Boards with the ISA bus has been allowed the opportunity to synchronize the work of the tire and
different microprocessor clock speed, allowing the devices,
performed on the expansion cards, work more slowly than the base
microprocessor. This was particularly relevant when the clock speed
processors exceeded 10-12 MHz. Now the system bus ISA has been working
asynchronous processor at a frequency of 8 MHz. Thus, the maximum speed
transfer theory can reach 16 MB / sec.