IBM System/370 Guide

PROCESSOR (MAIN) STORAGE
Processor storage is available in the following increments:
Model
CaEacity
I
512K
J
1024K
JI 1536K
K
204SK
KJ
3072K
In order to achieve interleaving in the Model 165, the processor
storage present in the system is divided into logical memories within
storage boxes. A logical memory is defined as that portion of storage
that can operate independently from all other storage. A logical
memory in the Model 165 is 12SK or 256K and there are two per storage
box.
Depending on the storage size, the total number of logical memories
present is 4 in two boxes for Models I and J, S in four boxes for
Models K and JI, or 12 in six boxes for Model KJ, as shown in Figure
10.15.1. (Model JI, not shown, consists of four 12SK and four 256K
logical memories in two boxes.) However, only four logical memories
can be active at one time, thus achieving four-way interleaving. As
illustrated in Figure 10.15.1, for a 512K system, four consecutively
addressed doublewords are spread across logical memories so that 32
consecutive bytes can be accessed concurrently (one doubleword from
each of four logical memories, requested one SO-nanosecond cycle apart).
That is, processor storage location 0 is in logical memory 0, location
8 is in logical memory 1, location 16 is in logical memory 2, and
location 24 is in logical memory 3. Processor storage location 32
is in logical memory 0(, and the address distribution sequence continues
through all available storage locations.
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IBM System/370 Specifications

General

Brand	IBM
Model	System/370
Category	Server
Language	English