Atari 130XE Manual de usuario descargar pdf (Pagina 37)

4 512k RAM extension

The built-in RAM extension of the

TURBO FREEZER

is compatible with the wide spread

Rambo/ATARI-Magazin extensions. Bit 4 of

PORTB

activates access to the extension (0

= extended RAM at $4000. . . $7FFF enabled, 1 = internal Atari RAM enabled). The

bits 2,3,5,6 and 7 select one of the 32 16k banks. A separate ANTIC access, as it is present

in the Atari 130 XE and some other extensions, is not supported. On the one hand, the

required HALT signal is not available on the PBI bus. On the other hand, there are only

very few demos which require this mode. And meanwhile most of them have been patched

to work with RAM extensions that do not support separate ANTIC access.

The following restriction may arise with programs which require a RAM extension with

separate ANTIC access. If a RAM extension which supports separate ANTIC access

is present in the Atari, activating the built-in 512k RAM extension of the freezer may

cause malfunction. If ANTIC access to the RAM extension is enabled (via bit 5 of

PORTB

), but CPU (or combined CPU/ANTIC) access is disabled (via bit 4 of

PORTB

the ANTIC will access the internal RAM extension instead of the RAM extension of the

TURBO FREEZER

. The best solution is to prevent this situation by disabling either of

the RAM extensions.

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Atari 130XE Manual de usuario Pagina 37