Browse Prior Art Database

Dynamic Overlap Detection

IP.com Disclosure Number: IPCOM000106820D
Original Publication Date: 1993-Dec-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 2 page(s) / 73K

Publishing Venue

IBM

Related People

Cowan, B: AUTHOR [+2]

Abstract

A mechanism is described for determining destructive storage operand overlap for complicated ESA/390* instructions such as MOVE LONG (MVCL) and MOVE WITH KEY (MVCK) that allows reuse of microcode by sharing code between the simple SS type ESA/390 instructions such as MOVE CHARACTER (MVC), and MVCL, and MVCK instructions thereby reducing the control store address space requirements and development test time. In addition, the mechanism is faster than previous overlap determination schemes.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Dynamic Overlap Detection

      A mechanism is described for determining destructive storage
operand overlap for complicated ESA/390* instructions such as MOVE
LONG (MVCL) and MOVE WITH KEY (MVCK) that allows reuse of microcode
by sharing code between the simple SS type ESA/390 instructions such
as MOVE CHARACTER (MVC), and MVCL, and MVCK instructions thereby
reducing the control store address space requirements and development
test time.  In addition, the mechanism is faster than previous
overlap determination schemes.

      The logic mechanism is shown in the Figure.  It consists of
hardware and microcode means for controlling the inputs to the
destructive storage operand detection circuitry, and microcode
algorithms for utilizing this mechanism to detect storage operand
overlap.

      For all the SS format ESA/390 instructions, hardware initially
sets the input to the destructive storage operand overlap detection
circuitry, by means of instruction decode and setup logic, to be the
bases and displacements for the source and destination storage
operands, as well as the operand length so that the operand overlap
conditions are known to the first microinstruction executed.  The
destructive storage operand detection circuitry detects overlap in
one cycle from these inputs.  Subsequent microinstructions in an
ESA/390 instruction routine are given control of the inputs to the
overlap detection circuitry.  The inputs to the overlap detection
circuitry are either held, or set from a plurality of sources
including general purpose registers, bypass busses, set to zero, etc.
The hardware setup of the inputs during ESA/390 instruction text
decode and setup allows the fast determination of destructive storage...