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William Smith, who still own a DEC Pro 350, reports
to us:
The video was really weird (but not as weird as the Apple //e with the
Extended 80-column card). There were two ways to do color (or at least
gray-scale). The normal way was to buy the Extended Bitmap Option
(EBO) board, which on the Pro 325 and 350 gave you three planes of video
(8 simultaneous colors) from an 8-bit palette (256 possible RGB colors,
with 3 bits for red, 3 bits for green, and 2 bits for blue). The Pro
380's EBO board gave 3 planes of video from a 12-bit palette (4096
possible RGB colors, with 4 bits each for red, green , and blue).
Also, the Pro 325/350 EBO board was a normal expansion card, while the Pro
380 EBO board was a daughter card which plugged directly into the
motherboard, thus saving a slot.
The second way to get "color" (it was really gray-scale) was to
use an alternate video mode which traded resolution for color. For a
monochrome system (one video plane), the normal video mode was black and
white at 1024x256, of which 960x240 was available to the application.
The two alternate video modes gave 4 or 16 simultaneous shades of gray by
reducing the resolution to 512x256 or 256x256, respectively. These
video modes were never used on any commercial software (that I know of,
anyway).
It was also possible to use these alternate video modes in combination
with an EBO board, which gave 4096 simultaneous RGB colors at 256x256
pixels (on a color monitor, which I didn't have).
_______________________
About the number of expansion cards in the base systems. All Pro 300
series machines had six expansion slots, configured as follows:
Pro 325
1: empty (Pro 325 + hard disk = Pro 350)
2: floppy disk controller
3: standard video controller
4: empty
5: 256KB memory (+ 256KB on mobo = 512KB)
6: empty
Pro 350
1: hard disk controller
2: floppy disk controller
3: standard video controller
4: empty (I had the optional EBO board)
5: 256KB memory (+ 256KB on mobo = 512KB)
6: empty (I had an Ethernet board here)
Pro 380
1: hard disk controller
2: floppy disk controller
3: empty (standard video was on the motherboard)
4: empty
5: empty (512KB all on the motherboard)
6: empty
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