Specifications

CHAPTER 2
Architecture
Address Map 23
One way of using sound record with playthrough is in the recording of sounds from a
CD or CD-ROM.
IMPORTANT
As in the Macintosh LC, the sound mode is selected by means of a call
to the Sound Manager. To prevent feedback that might be audible, an
application should not let the user select select playthrough mode when
either microphone has been selected as the sound input source. For more
information, see the section “Sound Control Panel” beginning on
page 41. ▲
Sample Rates 2
The Macintosh LC 520 computer records and plays back sound at either of two sample
rates: 11k samples per second and 22k samples per second. For sound input, the system
switches the input filter between two cutoff frequencies that correspond to the two
sampling rates: 3.5 kHz cutoff for the 11k sample rate and 7 kHz cutoff for the 22k sample
rate.
Similarly on playback, the system switches between a filter with a 3.5 kHz cutoff
frequency for sounds at 11k samples per second and a 7 kHz filter for sounds at 22k
samples per second.
Address Map 2
The Macintosh LC 520 computer supports both 24-bit and 32-bit addressing. Figure 2-2
on page 24 shows the relationship between the 24-bit addresses and the 32-bit addresses.
The address map is similar to that of the Macintosh LC III.
Note
Developers should not use actual hardware addresses in applications but
should always communicate with hardware devices by means of system
software. ◆
RAM Addresses 2
The first 1 GB of the address space is reserved for RAM. The actual amount of RAM
installed can be from 4 MB to 36 MB. At startup time, a routine in the ROM determines
the amount of RAM available and stores the size in a low-memory global variable.