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Browse Prior Art Database

Propagation Delay Adjustment for AGP Strobe

IP.com Disclosure Number: IPCOM000123037D
Original Publication Date: 1998-Apr-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 1 page(s) / 48K

Publishing Venue

IBM

Related People

Sugiyama, M: AUTHOR

Abstract

Disclosed is a circuit pattern that is an easy to adjust for propagation delay between AGP (Accelerater Graphics Port) strobe and data bus. This AGP is a graphic bus advocated by INTEL co, and requires high speed operation (133Mhz). It has three signal groups and the strobe signal must be grouped with their associated data group as, AD_STB0 with AD(15:0) and C/BE(1:0) AD_STB1 with AD(31:16) and C/BE(3:2) SB_STB with SBA(7:0)

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Propagation Delay Adjustment for AGP Strobe

        Disclosed is a circuit pattern that is an easy to adjust for
propagation delay between AGP (Accelerater Graphics Port) strobe and
data bus.
  This AGP is a graphic bus advocated by INTEL co, and requires high
speed operation (133Mhz).  It has three signal groups and the strobe
signal must be grouped with their associated data group as,
  AD_STB0 with AD(15:0) and C/BE(1:0)
  AD_STB1 with AD(31:16) and C/BE(3:2)
  SB_STB  with SBA(7:0)

        Each line length mismatch should be 0.5-inches with the
strobe being the longest trace of the group to avoid timing skew
problems.  This rule is very hard for card physical design, because
real wiring between the interface connector and graphic device
depends on their placement.  And there are many restrictions (eg,
height restriction,  card out-line restriction, placement of other
required supporting components).  So we have to cut and try many
times to adjust this timing  skew, with the signal pattern changing
(it takes a lot of expense and hours of raw card change).  To reduce
this ineffectiveness, a new CDB (Component Data Base) model of many
length patterns should be prepared,  (Refer to figure).  The result
of this design approach is that it's possible to make timing
adjustment without rewiring raw card just by adding or removing
solder bridges.