Apple Logic Board Información técnica descargar pdf (Pagina 27)

ters. The file RAMEXPAND is the portion of the system which

resides in the Saturn RAM board. RAMEXPAND.LOW is the portion

which resides in low RAM (normally at HIMEM). This low RAM

portion of RAMEXPAND can actually be loaded and executed anywhere

in low RAM (0 — 48K), although it is normally located at HIMEM,

with HIMEM being lowered to protect it.

C. DATA STRUCTURE

RAMEXPAND saves and recalls selected parts of program text

or data. Each portion is saved in an independent area in

extended RAM. These areas are called segments. Each segment can

contain a program, a part of a program, or the contents of an

array. When information is saved in a segment, it must be given

a name. When the information is retrieved, it is identified with

this name. The “names” are in fact integers, and can be

specified as variables which contain the segment names when

calling RAMEXPAND, if desired. Segment names may be integers

between 1 and 32,767. Zero, negative numbers, or numbers greater

than 32,767 are illegal segment names.

D. MEMORY ALLOCATION

RAMEXPAND uses areas of the memory indicated as being

available on one or more Saturn 32K, 64K, or 128K RAM Boards as

well as on a 16K RAM board. RAMEXPAND treats each 16K bank of a

given memory card as consisting of two blocks of memory, one

which is 12K in size, and the other 4K. Thus a Saturn 32K board

consists of 4 blocks, two 12K blocks and two 4K blocks, a 64K

card consists of 8 blocks, and a 128K card consists of 16 blocks.

On the other hand, a 16K board contains only 2 blocks, one 12K

and one 4K.

Specific numbers have been assigned to these blocks and are

used for specifying a particular block. Numbers are used to

identify the blocks to be used by RAMEXPAND when the system is

initialized.

The RAM boards can be divided into two groups based on the

block designation numbers. The first group consists of 16K RAM

boards and the Saturn 32K RAM board, and the second group, the

Saturn 64K and 128K boards.

1. SATURN 32K RAM Board and 16K RAM Board

The memory organization of a Saturn 32K RAM board is given

in the following figure. The particular number used to designate

the depicted block is shown in brackets.

1 2 ... 22 23 24 25 26 27 28 29 30 31 32 ... 76 77

Sin comentarios

Apple Logic Board Información técnica Pagina 27