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The Small Buffer, Volume 527, l May 1980

RSX-11IM V3.2
JOHN L. HENNING, WPS DEVELOPMENT, CENTRAL COMMERCIAL ENGINEERING, MK1-2/G1$

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SAVING MEMORY UNDER RSX-1IM V3.2

Only two PDP-11s support memory sizes greater than 124K words:
the 11/44, and the 11/70. Since RSX-11M-PLUS is the natural

ehoice on the %4 and 70, most use of RSX-11M should be on

machines which have relatively small amounts of memory. Unfor-
tunately, the default RSX-11M V3.2 Sysgen options do: not make
optimal use of memory on small systems.

Do the following to tailor an RSX-11M V3.2 system to a memory-
limited machine:

1.  SYSVMR.CMD sets the size of POOL to the maximum. If
you don't need that much, ehange it.

2. For systems with the full duplex terminal driver,
SYSVMR sets TTPAR to 8K words, but it can usually be
made much smaller. TTPAR contains code plus a
private buffer pool, which is allocated in 20 word
ehunks for type-ahead buffers, UCB extensions, and
i/o-pending buffers. Since the space needed for the
i/o-pending buffers depends on both system activity
and the sizes of the i/o reguests, an exact sizing
guideline cannot be given. A rough guideline for
sizing TTPAR is:

P z: C 4 (20 ? T) > (60 8 A)

P is the size of TTPAR in decimal words

C is the code size (from the line "TASK IMAGE
SIZE" in [1,34]TTDRV.MAP)

T is the number of terminals in the system

A is the number of users likely to be ACTIVELY
typing at one time

Where

The value obtained for P is in decimal words; convert
to octal bytes/100 for the TTPAR SET /MAIN command.
If space is exhausted in  TTPAR, the driver will
attempt to use the system pool, so if you're short on
system pool, pad TTPAR for comfort.

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