With the advent of the new microprocessors, such as i80386 and i486, it became apparent
that one is insurmountable obstacles to improving productivity
computers with these microprocessors is a system bus ISA. In fact,
that the capacity of the tire to build high-performance systems
the next generation were virtually exhausted. The new system bus must
was to ensure the highest possible level of reporting to the memory 32-bit
data transmission, including in the DMA, an improved system interruptions and
Arbitration DMA, automatic system configuration and expansion cards. This tire
for the IBM PC-compatible computers became EISA (Extended Industry Standard
Architecture). Note that the Boards of EISA bus were originally
focused on specific applications is a new architecture and
It was on computers equipped with high-speed external memory subsystems
Hard drives with the buffer cache. Such computers are still
used mainly as a powerful file server or workstation.
In EISA-connector on the motherboard than the computer, of course, special
EISA-cards can be inserted either 8 - or 16-bit card expansion,
for an ordinary PC / AT bus with the ISA. This provides a simple,
but truly brilliant designs. EISA-jacks have two rows
contacts, one of which (top) uses signals tire ISA, and the second
(lower) - respectively EISA. Contact Connector EISA are so
that next to each alarm contact is a contact Earth. " Thanks
This minimizes the likelihood of generating electromagnetic interference, as well as
reduced susceptibility to such interference.
The EISA bus was allowed to direct 4-Gbaytnoe address space available
180386/486 microprocessor. However, access to this space may not be
only the central processing unit, but the Governing Boards and devices such as bus master --
Chief subscriber (that is, devices that can manage data
tire), as well as devices having the opportunity to organize mode DMA. Standard
EISA supports multi-architecture for "smart" devices
(cards), equipped with its own microprocessors. Therefore, for example,
the hard disk controller, graphics controllers and network
handled independently, without downloading the main processor. Theoretically
maximum data transmission speed of the bus
EISA in the so-called batch mode (burst mode) can reach 33 MB / sec. In
normal (standard) mode, it is not superior to, of course, know a
for the ISA.
At the EISA bus provides a method of centralized management,
organized through a special device - a system arbitrator. Thus
supported by the leading devices used on the bus, but may also
Providing bus requesting devices on cyclical basis.
As for the tire ISA, EISA system has 7 channels of DMA. DMA-compliance functions
fully compatible with similar operations in the ISA-bus, although they may
occur somewhat faster. KontrolleryDMA are able to maintain
8 -, 16 - and 32-bit data transfer mode. In general, possible
one of the four cycles of exchange between the device and memory DMA
system. This ISA-compatible cycles, are used to transmit data 8 strokes
Tire cycles of type A, performed in a bar tire cycles type performed for 4
tact tires, and the cycles of type C (or burst DMA), in which data transmission occurs
one stroke tires. Types of cycles A, B and C have 8 -, 16 - and 32-bit
devices, which can automatically change the size (width) of data
in the transfer of appropriate size is not the memory. Most ISA-compatible
devices using DMA, can work in almost 2 times faster if they
will be programmed to use cycles A or B, rather than the standard (and
relatively slow) ISA-cycles. This performance is achieved only
by improving bus arbitration, and not at the expense of compatibility with the ISA.
Priorities DMA system may be a "rotary" (variables), or
rigidly set. Lines interruption tire ISA, which interrupt request
transmitted in the form of changes in levels of stress (fronts signals), strongly
exposed impact noise. Therefore, in addition to the usual signals
interruptions on the bus ISA, active only in its front, in the EISA
also interrupt the signals, active level. Moreover, for each
Abandonment choice of a scheme activity can be programmed
in advance. Indeed interruption, active front, stored in the EISA only
compatibility with "old" adapters ISA, servicing of requests for interruption
which manufactures a scheme sensitive to the front of the signal. It is clear that
Abandonment, active level, less susceptible to noise and interference than
common. By the same (in theory) on the same physical line may
send infinitely large number of interrupts. Thus, one
Line interruption can be used for multiple requests.
For a bus EISA provides automatic configuration
system. Each manufacturer of circuit boards for computers with the expansion bus EISA
together these supplies cards and special configuration files. Information from
These files used in the preparation of the work, which is
in the computer division of resources between individual cards. For the "old" cards
adapters the user must choose the correct position himself
DIP-perekdyuchateley (Fig. 25) and jumper, but the service program for
EISA-installed computers enables the relevant
switches on the monitor screen and gives some recommendations to correct them
installation. In addition to architecture EISA provision is
certain groups of I / O addresses for specific slots tires - each
socket expansion is targeted range of 4 KB, which also allows
avoid conflicts between individual cards EISA.
Note that computers that use motherboards with bus EISA, is
expensive. In addition, the bus was still taktiruetsya frequency of about 8-10 MHz, and
transfer rate increased mainly due to an increase in bit bus
data.