HLASM - ISK = Insert Storage Key
The opcode of the ISK instruction is X'09'.
- Obtain the storage key of a page of real storage.
- Register to receive the storage key.
- Register containing a page address.
- The processor inserts the storage key of the 2K or 4K page addressed by
the second argument into the low-order byte of the first argument.
- The condition code does not change.
- If the page address is not a fullword address the instruction fails.
The page address does not have to be on a page-boundary, however; any
fullword address within a page addresses the page in its entirety.
- SSK was intended to set the storage key.
- ISKE is now used to obtain the storage key of a
page of real storage.
- IVSK is now used to obtain the storage key of a
page of virtual storage.
- The ISK instruction was part of the original S/360 instruction set.
However, it is no longer supported; it has been replaced by the
ISKE instruction. Support for the ISK instruction
has been dropped when the 370/XA architecture was introduced.
- Independent of Amode or DAT, the page address is always a 24-bit real
- The storage key was returned in the low-order 8 bits of the 32-bit
register specified as the second argument in the following format:
- The first 4 bits (0 through 3) were the actual storage key.
- If fetch protect was installed (an optional feature on early machines),
the fetch-protect bit would be in bit 4.
- If DAT was installed the Change and Reference bits would be in bits
5 and 6. I don't know in which order.
- Initially the ISK instruction worked on 2K pages only. When 4K pages were
introduced, the ISK instruction was modified to address either a 2K page or
a 4K page, depending on the address specified and the way that specific page
Not available (yet).
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