Tyan Computer TOLEDO S5520 - Manual (Page 72)

72
Bus: a data pathway. The term is used especially to refer to the connection
between the processor and system memory, and between the processor and PCI or
ISA local buses.
Bus mastering: allows peripheral devices and IDEs to access the system memory
without going through the CPU (similar to DMA channels).
Cache: a temporary storage area for data that will be needed often by an
application. Using a cache lowers data access times, since the needed information
is stored in the SRAM instead of in the slow DRAM. Note that the cache is also
much smaller than your regular memory: a typical cache size is 512KB, while you
may have as much as 4GB of regular memory.
Cache size: refers to the physical size of the cache onboard. This should not be
confused with the cacheable area, which is the total amount of memory which can
be scanned by the system in search of data to put into the cache. A typical setup
would be a cache size of 512KB, and a cacheable area of 512MB. In this case, up
to 512KB of the main memory onboard is capable of being cached. However, only
512KB of this memory will be in the cache at any given moment. Any main memory
above 512MB could never be cached.
Closed and open jumpers: jumpers and jumper pins are active when they are “on”
or “closed”, and inactive when they are “off” or “open”.
CMOS (Complementary Metal-Oxide Semiconductors): chips that hold the basic
startup information for the BIOS.
COM port: another name for the serial port, which is called as such because it
transmits the eight bits of a byte of data along one wire, and receives data on
another single wire (that is, the data is transmitted in serial form, one bit after
another). Parallel ports transmit the bits of a byte on eight different wires at the
same time (that is, in parallel form, eight bits at the same time).
DDR (Double Data Rate): is a technology designed to double the clock speed of
the memory. It activates output on both the rising and falling edge of the system
clock rather than on just the rising edge, potentially doubling output.
DIMM (Dual In-line Memory Module): faster and more capacious form of RAM
than SIMMs, and do not need to be installed in pairs.
DIMM bank: sometimes called DIMM sockets, because the physical slot and the
logical unit are the same. That is, one DIMM module fits into one DIMM socket,
which is capable of acting as a memory bank.
DMA (Direct Memory Access): channels that are similar to IRQs. DMA channels
allow hardware devices (like soundcards or keyboards) to access the main memory
without involving the CPU. This frees up CPU resources for other tasks. As with