IBM System/370 145 Manual page 183

The size of the partition required for emulation depends on the 1400
system being emulated, including standard and special features,
input/output devices, buffers,
et~c.
The processor storage required for
the 1401/1440/1460 emulator is equal to the combined sizes of:
• Simulated 1401/1440/1460 stoz'age. Each position of 1400 storage is
simulated in one byte of Mod€~l 145 storage (for example, 8000
positions
=
8000 bytes).
• Emulator routines required to emulate the 1401/1440/1460 system
instructions, features, and
1./0
operations
• Tape, disk, and unit record buffers. The number and size of tape
and disk buffers are specifie:d by the user.
Approximate minimum 1401/1440/'1460 emulator ,processor storage
requirements for emulation of a 1.400 system with unit record operations
only, unit record/tape operations" or unit record/tape/disk operations
are shown below. For details about processor storage requirements, see
1401/1440/1460 DOS Emulator on Models 135/1Q,s/155 (GC33-2004).
Emulated 0Eerations
DOS Partition size (bytes)
1401/1440/1460 unit record 18K
+
1401/1440/1460 storage size
+
buffers
1401/1440/1460 unit record and
23K
+
1401/1440/1460 storage size
6 tapes
+
buffers
1401/1440/1460 unit record, 6 tapes,
27K
+
1401/1440/1460 storage size
4 disks
+
buffers
The 1400 CPU features and 1400 I/O devices and special fea~ures
supported and the Model 145 devices used for 1401/1440/1460 emulation
are given in Tables 40.10.1 and 40.10.2. Table 40.10.3 lists the 1400
I/O devices that are not supported.
Emulator performance will vary depending on user options, such as
number and size of buffers, the instruction mix of the 1401/1440/1460
programs, the format of tape files, and the priority of the partition in
which the emulator is running.
Emulator performance is impr'oved by:
1. Using double buffers and spanned record format for tape files in
lieu of single or shared buffers and 1400 record format. (A
shared buffer can be used by more than one I/O device.)
2. Using single buffers rathe:r than shared buffers for disk files
3. specifying device independence for emulating unit record
operations on a magnetic tape or di.rect access storage device
4. Generating the emulator without support for the 51-Column
Interchangeable Read Feed ,and Column Binary features and the
Select Stacker instruction
A Guide to the IBM System/370 Mod4el 145 173