China Crane Wafer Check Valve

The ISA bus was developed by a team lead by Mark Dean at IBM as part of
the IBM PC project in 1981. It originated as an 8-bit system and was
extended in 1983 for the XT system architecture. The newer 16-bit
standard, the IBM AT bus, was introduced in 1984. In 1988, the Gang of
Nine IBM PC compatible manufacturers put forth the 32-bit EISA standard
and in the process retroactively renamed the AT bus to "ISA" to avoid
infringing IBM's trademark on its PC/AT computer. IBM designed the 8-bit
version as a check valve buffered interface to the external bus of the Intel 8088
(16/8 bit) CPU used in the original IBM PC and PC/XT, and the 16-bit
version as an upgrade for the external bus of the Intel 80286 CPU used
in the IBM AT. Therefore, the ISA bus was synchronous with the CPU
clock, until sophisticated buffering methods were developed and
implemented by chipsets to interface ISA to much faster CPUs.
Designed
to connect peripheral cards to the motherboard, ISA allows for bus
mastering although only the first 16 MB of main memory are available for
direct access. The 8-bit bus ran at 4.77 MHz (the clock speed of the
IBM PC and IBM PC/XT's 8088 CPU), while the 16-bit bus operated at 6 or 8
MHz (because the 80286 CPUs in IBM PC/AT computers ran at 6 MHz in
early models and 8 MHz in later models.) IBM RT/PC also used the 16-bit
bus. It was also available on some non-IBM compatible machines such as
the short-lived AT&T Hobbit and later PowerPC based BeBox.
Madge 4/16Mbps TokenRing ISA NIC.
Ethernet 10Base-5/2 ISA NIC.
In
1987, IBM moved to replace the AT bus with their proprietary Micro
Channel Architecture (MCA) in an effort to regain control of the PC
architecture and the PC market. (Note the relationship between the IBM
term "I/O Channel" for the AT-bus and the name "Micro Channel" for IBM's
intended replacement.) MCA had many features that would later appear in
PCI, the successor of ISA, but MCA was a closed standard, unlike ISA
(PC-bus and AT-bus) for which IBM had released full specifications and
even circuit schematics. The system was far more advanced than the AT
bus, and computer manufacturers responded with the Extended Industry
Standard Architecture (EISA) and later, the VESA Local Bus (VLB). In
fact, VLB used some electronic parts originally intended for MCA because
component manufacturers already were equipped to manufacture them. Both
EISA and VLB were backwards-compatible expansions of the AT (ISA) bus.

From the originalcheckvalve
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