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CHAPTER 1
Hardware
10
RAM Expansion Interface
the WD90C26 manages its frame buffer differently than QuickDraw expects, Pangola
must perform byte packing and unpacking to support color modes other than 8-bit.
For example, in 1-bit mode QuickDraw expects that each byte in the frame buffer
represents eight pixels. For every byte QuickDraw writes to the frame buffer in 1-bit
mode, Pangola unpacks the bits and sends 8 bytes to the WD90C26. Similarly, Pangola
must pack 8 bytes into 1 byte each time QuickDraw reads a byte from the frame buffer in
1-bit mode.
Because the WD90C26 is optimized for 8-bit color mode, there is little advantage to
selecting a reduced bit depth. Apple recommends that application developers use 8-bit
mode whenever possible on the Macintosh PowerBook 165c.
Applications that manipulate the frame buffer directly must do so at a consistent bit
depth because Pangola always interprets pixel data based on the current video mode. For
example, attempting to write 8-bit data to the frame buffer while in 1-bit mode will
corrupt the frame buffer because Pangola will unpack each byte as described above.
Sending 1-bit data to the buffer while in 8-bit mode produces similar results because
Pangola will not perform the necessary conversion.
LCD Screen 1
The PowerBook 165c uses a high-contrast 640 x 400 pixel FSTN color display with .30 mm
dot pitch. The display is backlit by two CCFL bulbs located at the top and bottom of the
panel.
The inherent differences between LCD and CRT technologies make it a challenge to
precisely match colors displayed on the LCD with those on an external monitor. The
PowerBook 165c gamma table provides good color matching while minimizing flicker.
Developers should use the supplied gamma table unless there is a specific need to replace
it. Using a gamma table developed for RGB systems will produce poor results.
RAM Expansion Interface 1
The PowerBook 165c accommodates RAM expansion cards from 2 MB to 10 MB in
capacity, for a total of 14 MB RAM. The RAM expansion interface is electrically identical
to that of the PowerBook 180. However, the design of the PowerBook 165c provides more
physical space for RAM expansion cards than was specified for earlier PowerBook
computers, making it easier for developers to design high capacity cards.
The RAM expansion slot is located on the RAM/ROM board, in the same position as
earlier PowerBook models. Figure 1-4 shows the location of the RAM expansion
connector. Figure 1-5 shows the mechanical design guide for PowerBook 165c
RAM expansion cards. Refer to the
Macintosh PowerBook 160 and Macintosh PowerBook 180
Developer Note
for electrical design guidelines.