Appendix B Functional Description 201
VSIMM
Two versions of the SPARCstation 20 VSIMM are available: 4-Mbyte and
8-Mbyte. The maximum available VSIMM memory capacities, based upon possible
memory allocations, are as follows:
â– One VSIMM with seven DSIMMS: 8 Mbytes
â– Two VSIMMs with six DSIMMS: 16 Mbytes
The VSIMM contains a memory display interface (MDI) chip, a video buffer chip
(VBC), and a digital-to-analog converter (DAC). There is also pixel clock generation
circuitry on the VSIMM. The SPARCstation 20 uses 60-nanosecond VRAMs on the
VSIMM. VRAM densities are supported by the SMC and are listed in
TABLE B-3.
FIGURE B-3 illustrates the VSIMM memory system.
FIGURE B-3 VSIMM Memory System
TABLE B-3 VRAM Densities
VRAM Density VRAMs/VSIMM Capacity Type
1-Mbit 256K x 4 32 4-Mbyte 128-bit VRAM
2-Mbit 256K x 8 32 8-Mbyte 256-bit VRAM
CONTROL
SMC
ADDR [11]
DATA [128]
SIMM slot (8)
VSIMM
DSIMM
DSIMM
DSIMM
DSIMM
DSIMM
DSIMM
DSIMM
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