Peritek VCD-V, User Manual

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Peritek
Theory of Operation 4-11
VCT-V Display Memory Size
For a VCT-V with a 1280 x 1024 display, the minimum video memory is a
8 MB of byte-addressable memory, expandable to 16 MB. Each 32-bit
34020 longword is a pixel position, where bits 0-23 are primary and bits
24-31 are overlay. The overlay memory uses the low 4 bits of each byte.
Bits 28 and 29 are used for window type table, and bits 30 and 31 are valid
but not used.
4.8 System Memory
The 34020 has its own private 32-bit memory which is independent of the
video RAM (VRAM) configuration and timing. Obviously, the writemask
register is not used with system memory, because it would cause
unpredictable operation of the board. The system memory resources for
the graphics board are comprehensive, and consist of four components:
SIMM sockets for field upgradability and Flash EEPROM. Section 5.3.4
has address ranges and memory maps for the DRAM and EEPROM
memories.
SIMM Sockets
The graphics board is built with SIMM sockets because it allows
considerable manufacturing flexibility. 1 MB, 4 MB, 8 MB, 16 MB, and
32 MB units can be fit into the same slot, with only jumper changes
required to accommodate the different capacities. Peritek makes its own
SIMMs because most commercial vendors do not make modules short
enough to fit into the VMEbus form factor. The SIMM module must not
exceed .95 inches in overall height.
Flash EEPROM
The Flash EEPROM uses four 150 ns 32-pin PLCC 8-bit wide parts, for a
maximum capacity of 2 MB. The graphics board is designed to permit on-
board reprogramming. However, as yet no software has been released (to
customers) to support this.