EISA System Architecture

Figure 12-1 illustrates the relationship of the Intel EBC, ISP, Data Buffer and Address Buffer to the host, EISA/ISA and X-buses in the 82350 environment.

		Host Bus
Data		82358		Address		82357
Buffer
		EBC		Buffer
(Data Bus						ISP
Steering)

EISA/ISA Bus

X-Bus

Buffer

X Bus

Figure 12-1. The Intel EISA Chipset

EISA Bus Controller (EBC) and EISA Bus Buffers (EBBs)

General

The EBC is pictured in figure 12-2. Together with the Data and Address EBBs, the EBC provides the bridging, translation and data bus steering functions described in the previous chapter. The following sections describe each of the functional areas that comprise the EBC.

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Chapter 12: Intel 82350DT EISA Chipset

CPU Selection

These four inputs to the EBC indicate the host CPU type and its bus frequency. Table 12-1 defines the valid settings for these inputs. If the host CPU is integrated onto the system board, these pins should be permanently strapped to the appropriate state. When the host CPU resides on a plug-in card, however, the four CPU signals should be set to the appropriate state when the CPU card is inserted. This allows automatic configuration of the EBC to match the CPU card installed in the machine. CPU input patterns not specified in table 12-1 are reserved for future use.

Table 12-1. CPU Type/Frequency

	CPU3			CPU2			CPU1			CPU0			CPU Type/Frequency
	1		0			1			0				32-bits, 2x clock, 25MHz 80386
	1		0			1			1				32-bits, 2x clock, 33MHz 80386
	1		1			0			0				32-bits, 1x clock, 25MHz 80486
	1		1			0			1				32-bits, 1x clock, 33MHz 80486

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EISA System Architecture

	To Data Buffer	Data
		Buffer
		Control
		Address
	To Address Buffer	Buffer
		Control
		Host Bus
	Host Bus	Interface
		Unit
	Host Cache	Cache
		Support
	Reset Logic	Reset
		Control
		CPU
	CPU Select Lines	Select
	AENLE#	Slot-Specific
		I/O Support

Clock

Generator

Unit

ISA Bus

Interface

Unit

EISA Bus

Interface

Unit

ISP

Interface

Unit

I/O

Recovery

Logic

Test

Support

Clock Logic

ISA Bus

EISA Bus

ISP

LIOWAIT#

TEST1#

Figure 12-2. The Intel 82358DT EBC

136