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'Verify Write' Memory Verification Function

IP.com Disclosure Number: IPCOM000105370D
Original Publication Date: 1993-Jul-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Christianson, MD: AUTHOR [+2]

Abstract

To perform a memory verification test using 'verify write,' the microcode writes a pattern to the memory (usually the entire memory is written). If a 4-byte wide memory with an 8-bit ECC field is assumed, the hardware automatically generates the 8-bit ECC data based upon the 4 bytes of the data field and sends all 5 bytes to the memory. Then, the microcode simply sets a bit to enable the 'verify write' function and proceeds to write the same pattern to the memory again. Once again, the hardware automatically generates the 8-bit ECC data based upon the data the microcode is trying to 'write' to the memory.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 71% of the total text.

'Verify Write' Memory Verification Function

      To perform a memory verification test using 'verify write,' the
microcode writes a pattern to the memory (usually the entire memory
is written).  If a 4-byte wide memory with an 8-bit ECC field is
assumed, the hardware automatically generates the 8-bit ECC data
based upon the 4 bytes of the data field and sends all 5 bytes to the
memory.  Then, the microcode simply sets a bit to enable the 'verify
write' function and proceeds to write the same pattern to the memory
again.  Once again, the hardware automatically generates the 8-bit
ECC data based upon the data the microcode is trying to 'write' to
the memory.  But instead of writing the data to the memory once
again, the hardware actually reads the data stored in the memory,
including the previously generated ECC data, and automatically
performs a comparison of the 32 bits of actual data read from the
memory against the data the microcode is trying to 'write' to the
memory.  A comparison is also done of the 8 bits of ECC data read
from the memory against the ECC data generated by the hardware based
upon the data presented to it by the microcode.  If any bits within
the 32 bits of data and the 8 bits of ECC do not match, a
corresponding bit(s) is set in a 40-bit wide 'data verify' register.

      The contents of the 'data verify' register are cumulative; in
other words, the entire memory or any portion of it can be tested
using 'verify write' before the 'data ve...