Browse Prior Art Database

Flexibility Through Multiplexing a DOS/ Extender Passup Interrupt

IP.com Disclosure Number: IPCOM000121963D
Original Publication Date: 1991-Oct-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 2 page(s) / 63K

Publishing Venue

IBM

Related People

Manges, MG: AUTHOR [+3]

Abstract

"Passup" interrupts are software or hardware interrupts that are generated in real mode, taken by a DOS Extender kernel, which switches the processor into protected mode and reissues the interrupt. A method for reducing the number of "passup" interrupts required in a system is disclosed. This results in better system performance.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 64% of the total text.

Flexibility Through Multiplexing a DOS/ Extender Passup Interrupt

      "Passup" interrupts are software or hardware interrupts
that are generated in real mode, taken by a DOS Extender kernel,
which switches the processor into protected mode and reissues the
interrupt.  A method for reducing the number of "passup" interrupts
required in a system is disclosed.  This results in better system
performance.

      The DOS/Extender Execution Manager uses a predefined software
interrupt as the method used by applications running under its
control to perform requests.  This interrupt can also be used as a
"passup" interrupt to serve as a transparent mechanism for a mode
switch.

      To accomplish this, the DOS/Extender Execution Manager first
hooks the interrupt it intends to use.

      Next, it unhooks the chain completely by pointing the interrupt
vector at an interrupt return.

      It then defines that interrupt as a "passup" interrupt to the
extender kernel.

      Finally, it hooks the interrupt again to ensure that it owns
the interrupt again.

      Logically, at this point, the DOS/Extender Execution Manager
forms two separate chains at this point, removing the "passup" code
from the interrupt chain.

      Anytime here after, when an application issues an interrupt
that does not require a mode switch, the extender kernel is bypassed.
The "passup" never occurs and the interrupt sharing behaves as if the
interrupt has not been defined...