AT&T 3B2/300 Technical Reference Manual page 195

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CM522A VCACHE CARD
The CM522A Virtual Cache (VCACHE) Card improves system performance by storing instructions
and data used by the Central Processing Unit (CPU). Electrically, the VCACHE is located between the
CPU and the Memory Management Unit (MMU) and operates in parallel with the virtual-to-physical
translation of the MMU. Therefore, the CPU can retrieve information from the VCACHE faster than
from main memory via the MMU.
There is a software driver associated with the VCACHE feature. That driver is part of the reason
the computer must be running UNIX System V Release 3.1.1 or later.
The CM522A Card is a single-width card measuring 6.5 inches wide by 7.4 inches deep. The card
uses surface mounted technology. Figure 2-59 shows the component layout of a typical CM522A
VCACHE Card. Connector pinout information is provided in Appendix B. The major features of the
CM522A Card are listed below:
• Direct mapped operation using virtual memory addresses
• Allows the CPU access for cache hits resulting in zero CPU wait states
• Operates for frequencies up to 22 MHz
• 4K bytes of instructions and 2K bytes of data.
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