ISCAS High-Level Models

c2670 Benchmark Circuit
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High-Level Model of c2670


Statistics: 233 inputs; 140 outputs; 1193 gates

Function: 12-bit ALU and controller

This benchmark consists of an ALU with a comparator, an equality checker, and several parity trees. The comparator has two 12-bit inputs X and Y, and computes Y>X using a carry-lookahead adder (CLA) that performs the addition !X+Y. It can be programmed to do a 4, 6, 8 or 12-bit comparison of its inputs. An interesting feature of the comparator is that it uses two identical CLAs that have identical inputs, a redundancy technique commonly used in fault-tolerant systems. The CLAs have a fairly standard structure with 3, 4 and 5-bit blocks. The carry output signal of each CLA gives the result of (Y>X). The output labeled OutYgreaterX_Equal (line number 231) is constant 1 if the outputs of the two CLAs are identical, as would normally be the case. If, however, the CLAs produced different results, the OutYgreaterX_Equal output would be logic 0, implying an error in the circuit. This would happen, for example, if there were manufacturing defects in one of the CLAs.

Module M7 (EqualZ_W) performs an equality check on two 17-bit buses. The ParityChecker module (M8) contains five 10-input parity trees, whose outputs are all ANDed. This module seems to perform a sanity check on the input buses of c2670. There are also several small pieces of logic which are mostly random.



Inputs/Outputs vs. Netlist Numbers

Models:



* Netlist numbers for input buses A[9:0] and B[9:0]:

Input bus

0[lo]

1

2

3

4

5

6

7

8

9 [h]

A

A1

81

92

91

90

89

88

87

86

85

93

A2

43

54

53

52

51

50

49

48

47

55

A3

56

66

65

64

63

62

logc1

61

60

67

A4

68

79

78

77

76

75

74

73

72

80

B

B1

131

141

140

139

138

137

136

135

142

logic1

B2

95

105

104

103

102

101

100

99

106

logic1

B3

119

129

128

127

126

125

124

123

130

logic1

B4

107

117

116

115

114

113

112

111

118

logic1

* Input buses Y1[5:0], Y2[5:0], Y3[3:0]:

 

0 [lo]

1

2

3

4

5 [h]

Y1

1341

1348

1956

1961

1966

1971

Y2

1996

2067

2072

2078

2084

2090

Y3

1976

1981

1986

1991

-

-

* Inputs X[11:0] and Y[11:0] of CompareXY (M4):

 

0[lo]

1

2

3

4

5

6

7

8

9

10

11[h]

X

A[0]

A[1]

A[2]

A[3]

A[4]

A[5]

A[6]

A[7]

A[8]

B[0]

B[1]

B[2]

Y

Y1[0]

Y1[1]

Y1[2]

Y1[3]

Y1[4]

Y1[5]

Y3[0]

Y3[1]

Y3[2]

Y3[3]

Y2[0]

Y2[1]

Y2[0]

Y2[1]

Y2[2]

Y2[3]

Y2[4]

Y2[5]

* Inputs W[16:0] and Z[16:0] of Bitwise Comparator (M7):

 

0[lo]

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16[hi]

Z

A[0]

A[1]

A[2]

A[3]

A[4]

A[5]

A[6]

A[7]

A[8]

B[0]

B[1]

B[2]

B[3]

B[4]

B[5]

B[6]

B[7]

19

4

20

5

21

22

23

6

24

25

32

26

33

27

34

35

28

W

Y1[0]

Y1[1]

Y1[2]

Y1[3]

Y1[4]

Y1[5]

Y3[0]

Y3[1]

Y3[2]

Y3[3]

Y2[0]

Y2[1]

Y2[2]

Y2[3]

Y2[4]

Y2[5]

logic0

* Q[9:0], R[9:0], S[9:0] (inputs to ParityChecker M8) are three 10-bit buses multiplexed out of Y1, Y2, Y3 and ParTreeIns:

 

0 [lo]

1

2

3

4

5

6

7

8

9 [hi]

Q

Y1[2]

Y1[3]

Y1[4]

Y1[5]

Y3[0]

Y3[1]

Y3[2]

Y3[3]

Y2[0]

2474

R

Y1[0]

Y1[1]

2427

2430

2451

2454

2443

2446

2435

2438

S

Y2[2]

Y2[3]

Y2[4]

Y2[5]

Y2[1]

2096

2100

2678

logic0

logic0

* Netlist numbers for the remaining inputs:

Inputs

Netlist numbers

ContA0, ContA1

651, 543

ContB0, ContB1

2105, 2104

ContZ0. ContZ1

16, 29

ContEq

11

ContMask0,1,2

8, 1384, 40

ContAlpha

!B[5]. ContMask2. B[4]. !ContMask1

ContBeta

!B[5]. ContMask2. (!B[4] + ContMask1)

ContPar0,1,2,3

14, 37, 2106, 567

ParTreeIns[11:0]

(fanin of Q,R,S)

2096, 2100, 2678, 2454, 2451, 2446, 2443, 2438, 2435, 2430, 2427, 2474

InTbus[7:0]

108, 57, 120, 69, 96, 82, 132, 44

MiscRandomIns[11:0]

3, 1, 483, 36, 15, 2, 661, 7, 94, 1083, 2066, 452

MiscMuxIn

559

MiscMuxCont0,1

868, 860

* Netlist numbers for outputs:

Outputs

Netlist numbers

OutYgreaterX (Y>X)

329

OutYgreaterX_Equal

(Y>X)#1 == (Y>X)#2

231

OutZequalW (Z==W)

150

OutNot_ZequalW (Z != W)

311

OutParCheck

308

OutNot_ParCheck

225

ParChkOuts[7:0]

261, 325, 319, 401, 229, 227, 397, 395

OutTbus[7:0]

238, 237, 236, 235, 221, 220, 219, 218

MiscMuxOuts[10:0]

280, 321, 323, 331, 153, 148, 145, 297, 284, 282, 295

MiscBusOuts[12:0]

164, 160, 162, 171, 168, 166, 299, 301, 286, 303, 288, 305, 290

MiscRandomOuts[17:0]

158, 188, 176, 259, 234, 217, 223, 156, 173, 369, 367, 411, 384, 337, 409, 391, 350, 335


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