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Browse Prior Art Database

Enhanced Microcode Storage

IP.com Disclosure Number: IPCOM000102552D
Original Publication Date: 1990-Dec-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 50K

Publishing Venue

IBM

Related People

Grosbach, LE: AUTHOR [+3]

Abstract

Disclosed is a method which enables a storage control unit (SCU) function to fit on a cost-effective-size chip by the elimination of its on-chip microcode array registers. This non-cache storage enhancement allows the function to remain unchanged and keeps the design transparent to the microcode interface.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 84% of the total text.

Enhanced Microcode Storage

       Disclosed is a method which enables a storage control
unit (SCU) function to fit on a cost-effective-size chip by the
elimination of its on-chip microcode array registers.  This non-cache
storage enhancement allows the function to remain unchanged and keeps
the design transparent to the microcode interface.

      In the design of a storage control unit, a primary goal is to
minimize cell logic while keeping the design transparent to the
microcode interface.  This enables the use of a smaller,
cost-effective chip without requiring a rewrite of the microcode.  To
facilitate this goal, the microcode storage registers are moved from
on-chip to mainstore, and the hardware is modified to do the
equivalent function in accessing the registers.  A small number of
the frequently used registers, however, are left on-chip to allow for
faster access and better performance.  The microcode is also given
the flexibility to physically locate these registers anywhere in
mainstore by executing a control word indicating the offset starting
address.  The impact due to the extra logic and cycles required to
implement this storage mechanism is minimal in comparison to the
other alternatives which are:
   1.  Keep the arrays on-chip and use a bigger, more expensive chip.
   2.  Decrease the number of on-chip arrays which would cause a
significant rewrite of the microcode.
  3.  Take the microcode registers off-chip and let the microcode
cre...