L.s,
Recently I had my first system programmer course ( ES15 ).
It was meant as a MVS refresh-course but it contained a lot more
information than expected.
So now I am slowly working through the course materials checking if I
understand everything.
At the moment I am looking into 64-bit addressing and some things are
unclear.
The Principles of Operation didn't help as much as I hoped.
------------------------------------------------------
Short version questions:
- Are region tables filled back to front in blocks of 4096 bytes
( 512 * 64-bit entries )?
- Am I correct that the maximum needed storage for all the
tables is ~32 Petabyte?:
If I assume there are 5 Region-Second-Tables, then:
- Bit 58 ( region invalid bit ) of the entries 2044 to 2048 of
the Region-First-Table is 0?
- Bit 58 of entries 1537 to 2043 of the Region-First-Table is 1?
- Bits 0 - 51 of entries 1537 to 2043 of the First-Region-Table
are also 0?
------------------------------------------------------
Long version:
The first part of the address ( RFX, 11 bits ) is the index in the
Region-First-Table of the entry that points to the beginning of the
Region-Second-Table.
So far so good! Everything crystal clear.
Now the entry in Region-First-Table itself.
Bits 0 - 51 plus 12 zeros is the address of the correct
Region-Second-Table. Ok
Bits 52 - 55 are not used in region tables. Ok
Bits 56 - 57 : 0-3 * 4096 bytes is the length of the unused first part
of the Region-Second-Table:
- Region tables are filled back to front in blocks of 4096
bytes?
Bit 58 : Region-Invalid Bit. When the bit is one, the
Region-Second-Table associated with the entry is not valid.
So... If I assume there are 5 Region-Second-Tables, then:
- Bit 58 of the entries 2044 to 2048 of the First-Region-Table
is 0?
- Bit 58 of entries 1537 to 2043 of the First-Region-Table is 1?
- Bits 0 - 51 of entries 1537 to 2043 of the First-Region-Table
are also 0?
Am I correct that the maximum needed storage for all the tables is ~32
Petabyte?:
1 Region-First-Table 2048 entries of 8 bytes = 16.384 bytes +
2048 Region-Second-Tables 2048 * 2048 entries of 8 bytes =
33.554.432 bytes +
2048^2 Region-Third-Tables 2048^2 * 2048 entries of 8 bytes =
68.719.476.736 bytes +
2048^3 Segment-Tables 2048^3 * 2048 entries of 8 bytes =
140.737.488.355.328 bytes +
2048^4 Page Tables 2048^4 * 256 entries of 8 bytes =
36.028.797.018.963.968 bytes
Or am I making a horrible mistake somewhere?
--
Maarten Slegtenhorst
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