AM79C974 datasheet(125/153 Pages) AMD

125 / 153 page

AMD

P R E L I M I N A R Y

125

Am79C974

18681A-65

CPU

MEMORY

External

Peripheral

High-Density

SCSI-2

Termination

High-Density

SCSI-2

Connector

Keyboard

Connector

Bracketed card

joining ribbon cable

with high-density

SCSI-2 cable

External SCSI-2 Bus Cable

Internal SCSI bus cable

Connector for

Internal Peripheral

To DC Power

Ferrite Bead

To SCSI CLK1

and CLK2

Am79C974

to PCI Bus

always on

Figure E-3. Motherboard Layout — Approach #1

Layout #2

This approach uses a “pizza-box” type of motherboard,

which has been incorporated into PC systems and work-

stations. This design reduces the system’s height so

that its casing resembles a pizza box. This is partly the

result of a riser card that enables cards to rest on their

side instead of upright. This approach requires the fol-

lowing and is illustrated in Figure E-4:

An external connector mounted on the mothe-

rboard with routings that connect to the

Am79C974.

The Am79C974 must be as close as possible to

this external connector since this part of the SCSI

bus consists of motherboard routings (not just rib-

bon cable).

An internal connector on the motherboard to ac-

commodate internal drives.

On-board regulated terminators for SCSI drives

not mounted within the system. However, should

the user decide to connect a drive internally, termi-

nators are not needed.

If on-board regulated terminators are used, they

should be placed within .1 m (3.937 in) from the

Am79C974.

AM79C974 Datasheet(PDF) 125 Page - Advanced Micro Devices

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