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US5365463A
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Method for evaluating the timing of digital machines with statistical variability in their delays
Assignee: International Business Machines Corp
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Filing: 1990-12-21
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Granted: 1994-11-15
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Expires: 2010-12-21
Abstract
Abstract An apparatus and method for simulating timing performance of designs of digital machines which allows for the avoidance of lumping of correlation of correlation coefficients which may be significant to the slacks which may occur in a particular design. Delays of particular digital elements are derived by random selections from distributions of delay values based on correlations between different observed or otherwise reasonable distributions of relative delays of digital element pairs including pairs of senses of logic value transitions, pairs of technologies and pairs of packaging levels as an accuracy enhancement. Delay distributions are built up of weighted sums of other distributions and may be asymmetrical. Several computational enhancements disclosed include arrangements allowing reductions in paging (e.g. reduction in number of accesses to secondary memory). Other enhancements include application enhancements by providing generality of methodology and accommodation of large model size, further computational enhancement by providing generality of delay propagation algorithms and diagnostic enhancements by providing cycle time/yield data and allowance of re-simulation of failure modes of design performance by retaining seed values corresponding to simulated machines.
Inventors
- 👤 Wilm E. Donath
- 👤 Robert B. Hitchcock
- 👤 Jeffrey P. Soreff
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 12:18
CPC Classifications
G; G06; G06F; G06F11/00; G06F11/30; G06F11/34; G06F11/3457; G06F30/00; G06F30/30; G06F30/32; G06F30/33; G06F30/3308; G06F30/3312
Claims Analysis
Total Claims: 31
Claim 1
Independent Claim
61 words
An apparatus for simulating digital machine performance including: means for randomly selecting a delay of a particular digital element based upon at least one of a set of correlation factors descriptive of a correlation of delay distributions of said digital element and another digital element, and means for selecting a delay distribution from among at least two differently shaped delay distributions.
Claim 2
Independent Claim
61 words
An apparatus for simulating digital machine performance including: means for randomly selecting a delay of a particular digital element based upon at least one of a set of correlation factors descriptive of a correlation of delay distributions of said digital element and another digital element, and means for selecting a delay distribution from among at least two differently shaped delay distributions.
Claim 3
Independent Claim
82 words
A method of simulating digital machine performance with an apparatus including means for randomly selecting a delay of a particular digital element based upon at least one of a set of correlation factors descriptive of a correlation of delay distributions of said digital element and another digital element, said method including the steps of applying selected weights to a plurality of selected, normalized, uncorrelated distributions, and deriving at least two delay distributions as weighted sums of respective ones of said uncorrelated distributions.
Claim 4
Independent Claim
82 words
A method of simulating digital machine performance with an apparatus including means for randomly selecting a delay of a particular digital element based upon at least one of a set of correlation factors descriptive of a correlation of delay distributions of said digital element and another digital element, said method including the steps of applying selected weights to a plurality of selected, normalized, uncorrelated distributions, and deriving at least two delay distributions as weighted sums of respective ones of said uncorrelated distributions.
Claim 5
Dependent Claim
43 words
A method as claimed in claim 2, wherein said applying step is responsive to pairs of at least two of pairs of transition state senses, pairs of technologies and pairs of packaging level shared by said digital element and said another digital element.
Claim 6
Dependent Claim
27 words
A method as recited in claim 2, wherein at least one of said delay distributions is a differently shaped delay distribution than another of said delay distributions.
Claim 7
Dependent Claim
19 words
A method as recited in claim 4, wherein at least one of said differently shaped delay distributions is asymmetrical.
Claim 8
Dependent Claim
27 words
A method as recited in claim 2, wherein at least one of said delay distributions is derived as a weighted sum of at least two delay distributions.
Claim 9
Dependent Claim
19 words
A method as recited in claim 4, wherein at least one of said differently shaped delay distributions is asymmetrical.
Claim 10
Dependent Claim
27 words
A method as recited in claim 4, wherein at least one of said delay distributions is derived as a weighted sum of at least two delay distributions.
Claim 11
Dependent Claim
27 words
A method as recited in claim 5, wherein at least one of said delay distributions is derived as a weighted sum of at least two delay distributions.
Claim 12
Independent Claim
91 words
An apparatus for simulating digital machine performance including means for randomly selecting a delay of a particular digital element based upon at least one of a set of correlation factors descriptive of a correlation of delay distributions of said digital element and another digital element, said apparatus including means for storing a seed value corresponding to each of a plurality of simulated digital machines simulated by said apparatus, means for outputting at least said seed value corresponding to any simulated digital machine having a slack of less than a predetermined value.
Claim 13
Independent Claim
91 words
An apparatus for simulating digital machine performance including means for randomly selecting a delay of a particular digital element based upon at least one of a set of correlation factors descriptive of a correlation of delay distributions of said digital element and another digital element, said apparatus including means for storing a seed value corresponding to each of a plurality of simulated digital machines simulated by said apparatus, means for outputting at least said seed value corresponding to any simulated digital machine having a slack of less than a predetermined value.
Claim 14
Dependent Claim
27 words
An apparatus as recited in claim 10, further including means for analyzing ones of a plurality of digital machines for slacks of less than a predetermined value.
Claim 15
Dependent Claim
25 words
An apparatus as recited in claim 10, further including means for outputting a distribution of slacks of a predetermined number of said simulated digital machines.
Claim 16
Dependent Claim
37 words
An apparatus as recited in claim 11, further including means for simulating a particular digital machine with a seed value corresponding to one of said simulated machines having a slack which is less than a predetermined value.
Claim 17
Dependent Claim
24 words
An apparatus as recited in claim 13, wherein said slack which is less than a predetermined value is a slack for said simulated machine.
Claim 18
Dependent Claim
31 words
An apparatus as recited in claim 13, wherein said slack which is less than a predetermined slack is a slack corresponding to a segment of one of said simulated digital machines.
Claim 19
Independent Claim
135 words
A method of simulating digital machine performance with an apparatus including means for randomly selecting a delay of a particular digital element based upon at least one of a set of correlation factors descriptive of a correlation of delay distributions of said digital element and another digital element, said method including the steps of simulating a plurality of digital machines constituting a subset of said digital machines to derive a predetermined number of results of said simulation of said plurality of digital machines, summarizing said predetermined number of results of said simulation of said plurality of digital machines to produce a plurality of results and simulating a further plurality of said digital machines constituting a further subset of said digital machines, said plurality of results of said summarizing step numbering fewer than said predetermined number.
Claim 20
Independent Claim
135 words
A method of simulating digital machine performance with an apparatus including means for randomly selecting a delay of a particular digital element based upon at least one of a set of correlation factors descriptive of a correlation of delay distributions of said digital element and another digital element, said method including the steps of simulating a plurality of digital machines constituting a subset of said digital machines to derive a predetermined number of results of said simulation of said plurality of digital machines, summarizing said predetermined number of results of said simulation of said plurality of digital machines to produce a plurality of results and simulating a further plurality of said digital machines constituting a further subset of said digital machines, said plurality of results of said summarizing step numbering fewer than said predetermined number.
Claim 21
Independent Claim
93 words
A method for simulating digital machine performance with an apparatus including means for randomly selecting a delay of a particular digital element based upon at least one of a set of correlation factors descriptive of a correlation of delay distributions of said digital element and another digital element, said method including the steps of storing a seed value corresponding to each of a plurality of simulated digital machines simulated by said apparatus, outputting at least said seed value corresponding to any simulated digital machine having a slack of less than a predetermined value.
Claim 22
Independent Claim
93 words
A method for simulating digital machine performance with an apparatus including means for randomly selecting a delay of a particular digital element based upon at least one of a set of correlation factors descriptive of a correlation of delay distributions of said digital element and another digital element, said method including the steps of storing a seed value corresponding to each of a plurality of simulated digital machines simulated by said apparatus, outputting at least said seed value corresponding to any simulated digital machine having a slack of less than a predetermined value.
Claim 23
Dependent Claim
26 words
A method as recited in claim 17, further including the step of outputting a distribution of slacks of a predetermined number of said simulated digital machines.
Claim 24
Dependent Claim
28 words
A method as recited in claim 17, further including the step of analyzing ones of a plurality of digital machines for slacks of less than a predetermined value.
Claim 25
Dependent Claim
38 words
A method as recited in claim 19, further including the step of simulating a particular digital machine with a seed value corresponding to one of said simulated machines having a slack which is less than a predetermined value.
Claim 26
Dependent Claim
24 words
A method as recited in claim 20, wherein said slack which is less than a predetermined value is a slack for said simulated machine.
Claim 27
Dependent Claim
31 words
A method as recited in claim 20, wherein said slack which is less than a predetermined value is a slack corresponding to a segment of one of said simulated digital machines.
Claim 28
Independent Claim
136 words
An apparatus for simulating digital machine performance including means for randomly selecting a delay of a particular digital element based upon at least one of a set of correlation factors descriptive of a correlation of delay distributions of said digital element and another digital element, means for simulating a plurality of digital machines constituting a subset of said digital machines to derive a predetermined number of results of said simulation of said plurality of digital machines, means for summarizing said predetermined number of results of said simulation of said plurality of digital machines to produce a plurality of results, said plurality of results of said simulation of said plurality of digital machines numbering fewer than said predetermined number and means for simulating a further plurality of digital machines constituting a further subset of said digital machines.
Claim 29
Independent Claim
136 words
An apparatus for simulating digital machine performance including means for randomly selecting a delay of a particular digital element based upon at least one of a set of correlation factors descriptive of a correlation of delay distributions of said digital element and another digital element, means for simulating a plurality of digital machines constituting a subset of said digital machines to derive a predetermined number of results of said simulation of said plurality of digital machines, means for summarizing said predetermined number of results of said simulation of said plurality of digital machines to produce a plurality of results, said plurality of results of said simulation of said plurality of digital machines numbering fewer than said predetermined number and means for simulating a further plurality of digital machines constituting a further subset of said digital machines.
Claim 30
Independent Claim
68 words
An apparatus for simulating digital machine performance including means for randomly selecting a delay of each of a sequence of digital elements of said digital machine based upon at least one of a set of correlation factors descriptive of a correlation of delay distributions of said digital element and another digital element, means for accumulating said delays by traversing a plurality of said sequences of said digital elements.
Claim 31
Independent Claim
68 words
An apparatus for simulating digital machine performance including means for randomly selecting a delay of each of a sequence of digital elements of said digital machine based upon at least one of a set of correlation factors descriptive of a correlation of delay distributions of said digital element and another digital element, means for accumulating said delays by traversing a plurality of said sequences of said digital elements.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1997-11-14 | 1998-05-16 | 1998-11-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-11-14 | 2002-05-16 | 2002-11-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-11-14 | 2006-05-16 | 2006-11-15 | $7700.00 | Window Closed / Lapsed |