
Intel387
TM
DX MATH COPROCESSOR
4.3 AC Characteristics
Table 4.2a. i387 DX/i386 DX Interface and Execution Frequencies
Frequency (MHz)
i386 DX System
i387 DX 16-33
Execution Frequency (MHz)
Min
Max
16 MHz
20 MHz
25 MHz
33 MHz
10.0 MHz
12.5 MHz
15.6 MHz
20.6 MHz
22.4 MHz
28.0 MHz
33.0 MHz
33.0 MHz
NOTE:
The external clock frequencies for the i387 DX and i386 DX are
equal to twice the interface and execution frequencies show
above.
Table 4.2b. Timing Requirements of the Execution Unit
T
C
e
0
§
C to
a
85
§
C, V
CC
e
5V
g
5%
Pin
Symbol
Parameter
16 MHz–33 MHz
Conditions
Test
Reference
Figure
Min (ns)
Max (ns)
NUMCLK2
NUMCLK2
NUMCLK2
NUMCLK2
NUMCLK2
NUMCLK2
NUMCLK2
t1
t2a
t2b
t3a
t3b
t4
t5
Period
High Time
High Time
Low Time
Low Time
Fall Time
Rise Time
15
6.25
4.5
6.25
4.5
125
2.0V
2.0V
3.7V
2.0V
0.8V
4.1
6
6
3.7V to 0.8V
0.8V to 2.7V
Table 4.2c. Timing Requirements of the Bus Interface Unit
T
C
e
0
§
C to
a
85
§
C, V
CC
e
5V
g
5%
(All measurements made at 1.5V and 50 pF unless otherwise specified)
Pin
Symbol
Parameter
16 MHz–33 MHz
Conditions
Test
Reference
Figure
Min (ns)
Max (ns)
CPUCLK2
CPUCLK2
CPUCLK2
CPUCLK2
CPUCLK2
CPUCLK2
CPUCLK2
t1
t2a
t2b
t3a
t3b
t4
t5
Period
High Time
High Time
Low Time
Low Time
Fall Time
Rise Time
15
6.25
4.5
6.25
4.5
125
2.0V
2.0V
3.7V
2.0V
0.8V
4.1
6
6
3.7V to 0.8V
0.8V to 3.7V
NUMCLK2/
CPUCLK2
Ratio
10/16
14/10
READYO
Y
READYO
Y
(1)
PEREQ
BUSY
Y
BUSY
Y
(1)
ERROR
Y
t7
t7
t7
t7
t7
t7
Out Delay
Out Delay
Out Delay
Out Delay
Out Delay
Out Delay
4
4
4
4
4
4
17
15
25
21
19
25
4.2
C
L
e
25 pF
C
L
e
25 pF
D31–D0
D31–D0
D31–D0
D31–D0
(2)
t8
t10
t11
t12
Out Delay
Setup Time
Hold Time
Float Time
0
8
8
3
37
4.3
19
31
31