Cache On A STick
MODULE CONTAINING SRAM USED AS AN L2 CACHE IN MID-1990S COMPUTERS
Cache On A STick; COASt
<architecture> (COAST) <a href="">Intel Corporationa> attempt to's
standardise the modular <a href="">L2 cachea> subsystem in
<a href="">Pentiuma>-based computers.
A COAST module should be about 4.35" wide by 1.14" high.
According to earlier specifications from <a href="">Motorolaa>, a module
between 4.33" and 4.36" wide, and between 1.12" and 1.16" high
is within the COAST standard. Some module vendors, including
some major motherboard suppliers, greatly violate the height
specification.
Another COAST specification violated by many suppliers
concerns clock distribution in synchronous modules. The
specification requires that the clock tree to each synchronous
chip be balanced, i.e. equal length from edge of the connector
to individual chips. An unbalanced clock tree increases
reflections and noise.
For a 256 <a href="">kilobytea> cache module the standard requires the
same clock be used for both chips but some vendors use
separate clocks to reduce loading on the clock driver and
hence increase the clock speed. However, this creates
unbalanced loading in other motherboard configurations, such
as motherboards with soldered caches in the system.
(1996-06-10)