IBM System/370 Manual page 88

Page of GC20-17 3D-0
Revised 7/14/70
By TNL GN2D-2227
• Tapes containing files with records longer than 32,155 bytes (5461
7094 words) must be preprocessed by the tape formatting program.
Tapes written in seven- or nine-track 7094 mode can
be
used without
modification. (Consideration should be given to reblocking files
with short blocks in order to improve execution performance and
reblocking files with long blocks to reduce processor storage
buffer requirements.)
• Those 1094 programs that use unsupported I/O devices or facilities
can be modified to remove the unsupported facility and then
emulated, or they can be rewritten as System/370 programs.
The internal performance (that is, the speed of performing 7094
CPU instructions weighted by frequen.:=y of use) of the Model 165 7094
Emulator program is approximately 1.5 times that of the IBM 709411.
The throughput of emulated 7094 jobs executed on the Model 165 will
vary depending on job characteristics, resources available, etc. Total
system throughput increases should be achieved by operating 7094
emulator jobs in a multiprogramming environment.
40:20 70S0 EMULATOR PROGRAM
The 10S0 Emulator program for the Model 165 requires a Model 165
with the 10S0 Compatibility Feature (#111S), 512K or more of processor
storage, and enough I/O devices for the operating system and emulated
devices. In an MVT environment a 1024K minimum system is required
to emulate a 70S0 system with 160,000 positions of main storage. The
emulator program requires a minimum processing partition or region
of 232K for emulation of a 70S0 system with SOK. A 364K partition
or region is required to emulate a 10S0 system with 160K. These two
minimums support two channels and 14 tape units with one 2000-byte
buffer assigned to each tape data set. (Note that other considerations,
such as double buffering, I/O device configuration, performance, etc.,
will often necessitate use of an emulator partition or region larger
than these minimums.)
Table 40.20.1 lists 10S0 system features that are supported and
Table 40.20.2 indicates those that are unsupported. The 10S0 emulator
also can execute 705 I" II, and III programs that can be executed on
a 70S0, subject to the considerations and limitations outlined in the
IBM 10S0 Principles of Operation (GA22-6560) and in this document.
The Model 165 emulator supports the same facilities as the Mod·el 65
stand-alone 70S0 emulator.
The 70S0 Emulator program accepts and produces two tape data formats,
using BSAM:
66
1. 10S0 format tapes, written in BCD, that are written by a 7080
system, the Model 65 stand-alone 1080 emulator, the Model 165
integrated 70S0 emulator, or the Tape Postprocessor program.
These tapes can contain imbedded tapemarks but cannot contain
the reader storage mark character. Mixed density. seven-track
input tapes can be handled if single buffering is used and the
tape density specified in the DD statement is that of the first
record on the tape.
Tapes in 7080 format can be processed on nine-track tape drives
and 2400 tape drives with a seven-track head attached to a
control unit with the Seven-Track Compatibility Feature. They
must also be designated as unlabeled as far as OS is concerned
and their record format must be specified as undefined.