By TNL:
dresses is graphically depicted in the figure
"Relationship Between Real and Absolute Addresses.
fix register. The register has the following format:
corresponding to bit positions
prefix register are ignored.
provided for these bit positions. The prefix register is
age and to keys in storage, except for references by
a
during performance of the store-status function, and
except for references by a channel to extended
logout locations, to
address words, and to CCWs. When dynamic ad
dress translation is specified, prefixing is applied
after the address has been translated by the dynamic
address-translation mechanism. When installed,
prefixing is always active and is not subject to any
mode control.
When prefixing is applied, the storage address is
translated as follows:
1. Bits 8-19 of the storage address, if all zeros,
are replaced with bits 8-19 of the prefix.
2. Bits 8-19 of the storage address, if equal to bits
8-19 of the prefix, are replaced with all zeros.
3. Bits 8-19 of the storage address, if not all zeros
and not equal to bits 8-19 of the prefix, remain
unchanged.
In all cases, bits
main unchanged.
Only the address presented to storage is translat
ed by prefixing. The contents of the source of the
address remain unchanged.
The distinction between real and absolute ad
dresses is made even when prefixing is not installed
for
Relationship Between Real and Absolute Addresses
96
for