Macintosh LC II comes with either a 256K or 512K VRAM SIMM. The VRAM is
installed in a 32-pin SIMM slot. There are three possible SIMMs you can
use:
* NO VRAM (a SIMM containing two transparent latches)
- monochrome on Macintosh 12-inch Monochrome Display
- monochrome on 13-inch AppleColor High-Resolution RGB Monitor
- monochrome on VGA
* 256K VRAM SIMM option (Performa 405)
- 16 grays on Macintosh 12-inch Monochrome or VGA
- 256 colors on Macintosh 12-inch RGB Display
- 16 colors on 13-inch AppleColor High-Resolution RGB Monitor or VGA
* 512K VRAM SIMM option (Performa 400 and 430)
- 256 greys on Macintosh 12-inch Monochrome or VGA
- 32,000 colors on Macintosh 12-inch RGB Display
- 256 colors on 13-inch AppleColor High-Resolution RGB Monitor or VGA
Timing Modes
------------
The Macintosh LC II supports the following four video timing modes:
Resolution Supported Vertical Horizontal Bandwidth
---------- ------------------------ -------- ---------- ---------
512 x 384 Macintosh 12-inch RGB 60.15 24.48 15.67
640 x 480 Macintosh 12-inch Monochrome
AppleColor 13-inch 66.62 34.98 31.33
540 x 384 Macintosh 12-inch RGB
Macintosh 12-inch Monochrome
AppleColor 13-inch 60.15 24.48 17.23
VGA 59.94 31.47 25.18
All video timing modes use a 256 x 24 Color Look-Up Table (CLUT).
Monochrome mode also uses the CLUT, driving the R, G, and B with the same
signal. When you select "thousands of colors" in the Monitors control
panel, you're selecting 16 bit/pixel format. The 16 bit/pixel assigns the
uppermost bit to an Alpha Channel and 5 bits each for Red, Green, and Blue.
Selecting thousands mode divides the 256 x 24 CLUT into three 32 x 5
tables. Therefore, you get 2^15 = 32^3 = 32.7K color selections.
Monitor Video Connectors
------------------------
Macintosh LC II uses a DB-15 female connector to connect to the video
monitor. Here's the pin-out:
Pin Signal Description
--- ------ -----------
1 RED.GND Red Video Ground
2 RED.VID Red Video
3 CSYNC~ Composite Sync.
4 MON.ID1 Monitor ID, Bit 1
5 GRN.VID Green Video
6 GRN.GND Green Video Ground
7 MON.ID2 Monitor ID, Bit 2
8 nc (No Connection)
9 BLU.VID Blue Video
10 MON.ID3 Monitor ID, Bit 3
11 CSYNC.GND CSYNC Ground
12 VSYNC~ Vertical Sync.
13 BLU.GND Blue Ground
14 HSYNC.GND HSYNC Ground
15 HSYNC~ Horizontal Sync.
Shell S.GND Chassis Ground
Three of the 15 pins (pin 10, 7, and 4) are used to send a signal to
identify the monitor type. Once identified, Macintosh LC II synchronizes
the correct video timing.
The monitor IDs are:
Connector pins 10,7,4
Monitor ID bits 321
Macintosh 12-inch Monochrome 110
Macintosh 12-inch RGB Display 010
Apple IIe mode 010
AppleColor 13-inch RGB 110
VGA 011
No Monitor 111
When no monitor (111) is attached, 512 x 384 video timing is selected.
Macintosh LC II performs a special function of always returning a 1 to the
Monitor Parameters Register when reading Monitor ID bit 2. By performing
this special function, various monitors can select the correct video timing
schemes. The VGA monitor (011) has the same monitor ID as the two-page
monochrome. Neither the Two-Page nor the Portrait monitor can be attached
to Macintosh LC II.