Michael J. Mahon wrote:
It was briefly augmented with EISA (the Extended ISA) 16-bit bus
on some higher-end 286 and 386 systems--as an industry response
to the *licensed* PS/2 bus that IBM introduced.
A slight correction:
The ISA bus is both 8-bit and 16-bit, depending on whether the machine
was based on the 8088 (XT) or 8086 (AT) CPU's. Long black connector for
8-bit, the smaller black bit tacked up the front provides the extra 8
bits, plus the interrupt cascade, etc.
The IIgs is actually quite XT(8088) like in that it uses only an 8-bit
data bus, despite being a 16-bit CPU.
EISA is actually a 32 bit extension to ISA which floated around for a
while in "server class" (and I use the term loosely) 386/486 hardware.
It had a DMA mode which provided a fairly respectable 33mb/s
throughput. Useful primarily for SCSI subsystems where the extra I/O
speed actually utilisable.
Consumer oriented systems used the Vesa Local Bus, yet another 32 bit
extension to ISA intended primarily for video, but there were also VLB
I/O cards to provide higher bandwidth to IDE disks than was available
over the ISA bus. It didn't make much difference as I recall - the
disks available at the time were barely fast enough to soak up 16-bit
ISA bus bandwidth, but it did pave the way for the first serious use of
accelerated VGA cards for Windows 3.1
Systems had physical ISA busses alongside the PCI bus up until about
2001 or so. Pretty much all systems since then have done away with
them, although they still exist 'virtually' inside the motherboard
chipsets of every PC, except perhaps the new Mac machines.