Graphics Display Hardware

CS-321Dr. Mark L. Hornick

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Graphics Display Hardware

Display technologies CRT LCD Storage tube

Drawing methods Vector Raster

Architecture


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Sketchpad 1962 @ MIT Light pen Powered by “Whirlwind”,

MIT’s prototype of the 1st interactive computer

Req’d high bandwidth Vector display Monochromatic


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“Modern” Cathode Ray Tube (CRT)

Quasi-spherical screen

Phosphorescence period = 1/30 s to 1/60 s


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CRT – Sony Trinitron Slotted shadow mask Curvilinear screen Larger holes -- brighter image


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Vector Scanning• Electron beam can be arbitrarily directed• Number of displayable vectors is finite• Non-standard drive electronics


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1200-9600 baud serial

Begin

COLOR(a)MOVE(ix,iy)DRAW(ix,iy)

COLOR(b)DRAW(…)

End

Early hi-performance displays

MinicomputerDisplay Processor


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TektronixVector Display

T4010 512 x 512 ~$8,000

T4014 4096 x 3172 ~$18,000

PersistentStorage Phosphor

No digital memory


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Direct View Storage Tube

Two electron guns Primary electron gun draws the picture by knocking out electrons from the storage

grid, producing a positively charged pattern. Low speed electrons from the flood gun are attracted to the storage grid, and pass

through the positively charge pattern spots (past the collector grid) to hit the screen.

Once a picture is drawn it stays until erased by putting a charge over all of the storage grid so that the electrons hit all of the screen (producing a green flash on a green screen monitor).

Much cheaper then a regular random scan system did not require a built in CPU host computer was used to draw the image once


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1200-9600 baud serial

MOVE(ix,iy)DRAW(ix,iy)POINT(ix,iy)DASH(ix,iy,idash)


11Circa 1981


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Raster Scanning


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Video Display

Video graphics adapter Television monitor


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Early graphics adapters

Bus

CPU SystemMemory

Scan Converter

video, vga

Frame buffer

Pixel construction

• CPU constructs “virtual image” in System Memory • Scan converter reads virtual image and converts to video or vga signals

Graphics Display Hardware

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