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gate count 1476 number of cells 666 number of library cells 70 number of used cells 32 max fanin 17 max input capacitance 187 max internal fanout 34 critical path 0fF 2290 critical path 6fF 2960 |
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Now that the LOON optimisation starts with a netlist of x05 drive strength cells, the majority of the gates used are of x05 strength: 522 out of 666 cells. Yet the critical path has improved from 3056 to 2960, a 3.5% improvement, at the cost of an area increase of 1.4%. Another benefit of the x05 cells is a reduction in the input pin capacitance to the multiplier, from a previous max of 211fF down to 187fF.
The gate count has actually increased, even with a wider use of low drive strength cells. This in part is because the low drive cells have the same area as the immediately higher drive cells; and in part probably because the critical path improvement buffers up more cells where it is really useful.
The critical path shows that it consists mainly of higher drive cells.
fanout -- delay--
x 1 17 187
1 nd4v0x1 1 d->z 288 101
2 oai21v0x2 4 b->z 420 132
3 iv1v0x4 1 a->z 469 49
4 oai21v0x2 4 a2->z 607 138
5 iv1v0x4 1 a->z 656 49
6 oai21v0x2 4 a2->z 806 150
7 iv1v0x4 1 a->z 855 49
8 oai21v0x2 4 a2->z 992 137
9 iv1v0x4 1 a->z 1041 49
10 oai21v0x2 4 a2->z 1172 131
11 xnr2v0x1 1 a->z 1331 159
12 cgi2v0x2 3 b->z 1484 153
13 iv1v0x4 1 a->z 1534 50
14 cgi2v0x2 3 c->z 1645 111
15 iv1v0x2 1 a->z 1713 68
16 cgi2v0x2 3 c->z 1832 119
17 iv1v0x4 2 a->z 1890 58
18 nr2v0x2 1 b->z 1952 62
19 nd2v0x2 1 b->z 2019 67
20 oai21v0x2 3 b->z 2131 112
21 xnr2v0x1 1 b->z 2252 121
22 cgi2v0x2 2 c->z 2350 98
23 iv1v0x4 1 a->z 2400 50
24 cgi2v0x2 2 c->z 2485 85
25 an2v0x2 2 b->z 2605 120
26 an2v0x2 2 b->z 2732 127
27 nd2v0x2 1 b->z 2807 75
28 xnr2v0x2 0 a->z 2960 153
r 15 |
| Table of synthesis results | |||||||
| critical path (ps) | gate count | cell count | porosity | library cells | used cells | ||
| synthesis 1 | 4279 | 1561 | 923 | 43% | 9 | 8 | basic inverters, NAND & NOR gates |
| synthesis 2 | 4236 | 1472 | 792 | 45% | 15 | 12 | AND & OR gates |
| synthesis 3 | 4157 | 1357 | 696 | 46% | 19 | 16 | AOI & OAI gates, 2/1 and 2/2 |
| synthesis 4 | 4157 | 1357 | 696 | 46% | 20 | 16 | mxi2 2-way inverting mux |
| synthesis 5 | 3983 | 1343 | 668 | 48% | 21 | 16 | cgi2 carry generator inverting |
| synthesis 6 | 3948 | 1352 | 668 | 48% | 28 | 18 | inverters with multiple drive strengths |
| synthesis 7 | 3061 | 1433 | 666 | 51% | 70 | 27 | x2 drive strengths for all functions |
| synthesis 8 | 3056 | 1456 | 666 | 52% | 70 | 30 | BOOG with x1 drive strengths |
| synthesis 9 | 2960 | 1476 | 666 | 53% | 70 | 32 | BOOG with x05 drive strengths |
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