Browse Prior Art Database

Diagnostic Storage Operation

IP.com Disclosure Number: IPCOM000100279D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 66K

Publishing Venue

IBM

Related People

Fuhs, RE: AUTHOR [+4]

Abstract

Described is a means by which an externally connected test controller chip can set up an address and data for a double word transfer over a single word bus.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 55% of the total text.

Diagnostic Storage Operation

       Described is a means by which an externally connected
test controller chip can set up an address and data for a double word
transfer over a single word bus.

      A bus connecting to main store is 2 words wide. Processors,
memory cards and I/O interface cards share this bus.  A bus to
various I/O devices is 1 word wide. Diagnostic storage commands
originate from an external test controller chip, go over the 1 word
bus to the I/O inter face card, and then are sent to memory cards
over the 8-byte bus (see Fig. 1).  Diagnostic storage commands could
be used to write the memory with known data, possibly to initialize
memory that has parity.  The I/O bus format for writing to the
interface card from an external I/O device is a 1-word command
followed by two 1 word data transfers (see Fig. 2). A bus format for
writing to memory is as follows.  First a combination store command
and address is sent across the main store bus (see Fig. 3).  Then
data is sent a double word at a time.  Since main store cards access
data a double word at a time, store commands with less than a double
word of data to be stored use a read/modify/write (RMW) operation.
If data is uninitialized (does not contain good parity), then an
error will occur during a RMW of that location.  A simple write
operation will not first fetch data from main store and therefore
cannot get a parity error due to the data that was previously at that
location.

      As p...