Shadow Ram Option - Xycom XVME-678 Manual

Chapter
4 -
Programming
NOTE
The XVME-678/688 will not give up the VMEbus for the duration of step
3 even if the ROR option is selected.
This method may also be used to guarantee multiple consecutive VMEbus cycles by changing step 3 to
VMEbus master cycles.
4.5
SHADOW RAM OPTION
Shadowing is the process of loading the BIOS from EPROM into DRAM after power-up. Both the System
and VGA BIOS can be shadowed into DRAM to increase system performance.
On the 1 Mbyte version of the XVME-678/688, the 384 Kbytes of DRAM can be used to shadow the
BIOS or can be relocated to the address above the EPROMs as DRAM. The 2, 4, 10, and 16 Mbyte
versions of the XVME-678/688 always allocate 384 Kbytes of DRAM for shadowing the BIOS.
Because shadowing the BIOS increases system performance, the XVME-678/688 is factory-shipped with
the System BIOS and the Video BIOS shadowed.
Refer to Section 3.3.1.13 for more information on shadowing.
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