Browse Prior Art Database

Symmetrical Arbitration of Anti-Parallel Busses

IP.com Disclosure Number: IPCOM000113961D
Original Publication Date: 1994-Oct-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 4 page(s) / 92K

Publishing Venue

IBM

Related People

Goldrian, G: AUTHOR [+2]

Abstract

Described is a new arbitration scheme which takes care of a mapping-requirement by assigning bus grants to the operations requesting the interface so that an equal load is achieved on both busses.

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This is the abbreviated version, containing approximately 52% of the total text.

Symmetrical Arbitration of Anti-Parallel Busses

      Described is a new arbitration scheme which takes care of a
mapping-requirement by assigning bus grants to the operations
requesting the interface so that an equal load is achieved on both
busses.

      In case of a symmetrical interface that uses dedicated busses
for both directions, operation-mapping to that interface should be
done in such a way, that both dedicated busses have equal, maximum
load.  Fig. 1 shows one example of such symmetrical interface,
working with dedicated cable-lines for each direction, but there are
other interface-medias following the same requirements, e.g.,
fiber-optical links, infra-red- or radio-frequency-communications.

      The method to achieve this starts by dividing the operations
into two groups: those which transport data in one direction and
those which mostly use the opposite path.  Then the method tries to
alternately arbitrate an operation of the first group followed by an
operation of the second group and so on.

      To achieve this, the arbiter should know, how to detect, if an
operation wants to use the upgoing or the downgoing link for its
data-transfer.  In general, this is not so easy to predict in
advance, as usually only one request-line per Bus-requesting Unit
(BU) is wired to the arbiter, which does not allow to differentiate
between different operations to be granted.

      To get an information about the types of operation of the Bus
Units actually requesting the interface, our method is based on the
fact, that a standard Bus Unit does not only do a single
data-transfer over the link, but usually has to transfer a larger
block of data, e.g., one "page" of computer-data of 4096 bytes or a
disc-record of 512..1024 bytes, what results in a number of 16 to 32
data-transfers, depending on the width of the interface.

      Knowing this fact, which is nothing specific to our system, it
is very likely, that an request...