KU386 Datasheet, PDF(64/102 Page) Intel Corporation

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KU386 Datasheet, PDF (64/102 Pages) Intel Corporation – SX MICROPROCESSOR

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Intel386TM SX MICROPROCESSOR

Software Testing for Coprocessor Presence

When software is used to test for coprocessor

(Intel387 SX) presence it should use only the follow-

ing coprocessor opcodes FINIT FNINIT FSTCW

mem FSTSW mem and FSTSW AX To use other

coprocessor opcodes when a coprocessor is known

to be not present first set EM e 1 in the Intel386 SX

CPUâs CR0 register

6 0 PACKAGE THERMAL

SPECIFICATIONS

The Intel386 SX Microprocessor is specified for op-

eration when case temperature (Tc) is within the

range of 0 Câ100 C The case temperature may be

measured in any environment to determine whether

the Intel386 SX Microprocessor is within specified

operating range The case temperature should be

measured at the center of the top surface opposite

the pins

The ambient temperature (Ta) is related to Tc and

the thermal conductivity parameters ija and ijc from

the following equations (eqn 3 is derived by elimi-

nating the junction temperature (Tj) between eqns

1 and 2)

1) Tj e Tc a P ijc

2) Ta e Tj b P ija

3) Tc e Ta a P ija b ijc

Values for ija and ijc are given in Table 6 1 for the

100 lead fine pitch ija is given at various airflows

The power (P) dissipated by the chip as heat is

Vcc Icc A guaranteed maximum safe Ta can be cal-

culated from eqn 3 by using the maximum safe Tc of

100 C along with the maximum power drawn by the

chip in the given design and ijc and ija values from

Table 6 1 (The ija value depends on the airflow

measured at the top of the chip provided by the

system ventilation )

7 0 ELECTRICAL SPECIFICATIONS

The following sections describe recommended elec-

trical connections for the Intel386 SX Microproces-

sor and its electrical specifications

7 1 Power and Grounding

The Intel386 SX Microprocessor is implemented in

CHMOS IV technology and has modest power re-

quirements However its high clock frequency and

47 output buffers (address data control and HLDA)

can cause power surges as multiple output buffers

drive new signal levels simultaneously For clean on-

chip power distribution at high frequency 14 Vcc

and 18 Vss pins separately feed functional units of

the Intel386 SX Microprocessor

Power and ground connections must be made to all

external Vcc and Vss pins of the Intel386 SX Micro-

processor On the circuit board all Vcc pins should

be connected on a Vcc plane and all Vss pins

should be connected on a GND plane

POWER DECOUPLING RECOMMENDATIONS

Liberal decoupling capacitors should be placed near

the Intel386 SX Microprocessor The Intel386 SX Mi-

croprocessor driving its 24-bit address bus and

16-bit data bus at high frequencies can cause tran-

sient power surges particularly when driving large

capacitive loads Low inductance capacitors and in-

terconnects are recommended for best high fre-

quency electrical performance Inductance can be

reduced by shortening circuit board traces between

the Intel386 SX Microprocessor and decoupling ca-

pacitors as much as possible

Package

100 Lead

Fine Pitch

Table 6 1 Thermal Resistances ( C Watt) ijc and ija

ija versus Airflow - ft min (m sec)

ijc

200

400

600

800

(0)

(1 01)

(2 03)

(3 04)

(4 06)

34 5

29 5

25 5

22 5

21 5

1000

(5 07)

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