Installing Dram - Xycom XVME-678 Manual

Chapter
2 -
Installation
2.7 INSTALLING DRAM
The XVME-678/688 has four SIMM sites in which to add memory. Due to the 25 MHz CPU speed, the
access time of the DRAM interface is very important. To run at 0 wait states, the SIMMs must have the
following access times:
• 60 ns access time for nine chip DRAM SIMMs
• 70 ns access time for three chip DRAM SIMMs
If you opt for 80 ns DRAMs, change the 0 wait state option to 1, wait state in the Setup Menu.
NOTE
Three-chip memory modules are recommended to meet the VME height
specifications.
The XVME-678/688 can accommodate 1, 2, 4, 10 or 16 Mbytes of DRAM, mounted on SIMM strips.
SIMM strips with 256Kx9, 1Mx9, or 4Mx9 DRAM may be used. The table below lists the combinations
needed for the five memory configurations. (The bank location is silk screened on the back of the board.)
Table 2-16. Bank and SIMM Size
Memory
Bank 0 low Bank 0 high Bank 1 low
Bank 1 high
1 Mbyte
265Kx9 265Kx9 256Kx9 256Kx9
2 Mbytes 1Mx9 1Mx9
N/A
N/A
4 Mbytes 1Mx9 1Mx9
1Mx9 1Mx9
10 Mbytes 1Mx9 1Mx9 4Mx9 4Mx9
16 Mbytes 4Mx9 4Mx9 4Mx9 4Mx9
1 !I1hyte A1envry
The 1 Mbyte DRAM is divided into 640 and 384 Kbyte blocks for 80386SX accesses when the Shadow
RAM option is not enabled. The 640 Kbyte block resides from 000000-09FFFF; the 384 Kbyte block
from 100000-15FFFF. If the shadow RAM option is enabled, the DRAM is reduced to the lower 640
Kbytes of DRAM.
Four 256Kx9 memory SIMMs are needed for the 1 Mbyte configuration.
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