Browse Prior Art Database

Synchronization of Multiprocessors

IP.com Disclosure Number: IPCOM000082322D
Original Publication Date: 1974-Nov-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Holtz, CD: AUTHOR [+4]

Abstract

This is a process for producing cycle-by-cycle synchronization of two processors in a multiprocessing system.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 87% of the total text.

Page 1 of 2

Synchronization of Multiprocessors

This is a process for producing cycle-by-cycle synchronization of two processors in a multiprocessing system.

In a first CPU, herein called the local CPU, a microinstruction is executed which is simply a loop upon itself for all succeeding machine cycles. In the second CPU, herein called the remote CPU, a microinstruction is executed which provides a signal to the local CPU. The remote CPU then enters a succession of three null cycles.

On the first of those null cycles, the signal previously issued is transmitted to the local CPU. On the second null cycle, the local CPU executes a micro branch from the loop in response to the received signal, in order to execute the next function. That function is a null cycle and thus both processors are made to execute a null cycle simultaneously. Consequently, an instruction, such as Compare and Swap can be issued on the next cycle at the exact same time on both machines.

If the storage location referenced by the Compare and Swap is exactly the same on both processors, the locking mechanism which allows access to only one processor is forced to function. In that manner its proper operation can be observed.

Figs. 1 and 2 are flowcharts of the programs which are executed on the two processors, to perform the synchronizing function in an IBM System/370 multiprocessor. It should be noted that the Diagnose instruction invokes the microcode described above. Thus it is important to issue the Diagnos...