Cache on a stick

COASt, an acronym for "cache on a stick", is a packaging standard for modules containing SRAM used as an L2 cache in a computer. COASt modules look like somewhat over-sized SIMM modules. These modules were somewhat popular in the Apple and PC platforms during early to mid-1990s, but with newer computers cache is built into either the CPU or the motherboard. COASt modules decoupled the motherboard from its cache, allowing varying configurations to be created. A low-cost system could run with no cache, while a more expensive system could come equipped with 512 KB or more cache. Later COASt modules were equipped with pipelined-burst SRAM.

The standard was originally defined by Motorola to be between 4.33 and 4.36 inches (110 and 111 mm) wide, and between 1.12 and 1.16 inches (28 and 29 mm) high. It could be found in many Apple Macintosh in the early-to-mid-90s, but disappeared as the Mac moved to the PowerPC platform.

Intel also used the COASt standard for their Pentium systems, where it could be found as late as 1998 in Pentium MMX systems utilizing Intel chipsets such as 430VX and 430TX. Later, Intel combined this architecture with the CPU and created the Slot 1 CPU cartridge which contained both the CPU and separate cache chips.

The slot that the COASt module plugged into was named "CELP", or "card edge low profile", referring to the small circuit board and the conductors on its edge.

References

* [http://www.pcguide.com/ref/mbsys/cache/structCOASt-c.html COASt Modules] , PCGuide, April 17, 2001.
* [http://www.pcguide.com/proc/physinst/coast.htm Cache Module Physical Installation Procedure] , PCGuide, April 17, 2001.
*Renn, Brian. [http://www.cs.umd.edu/class/fall2001/cmsc411/projects/ramguide/cache/cache.html#whatCOASt The Cache Guide: What is COASt?] , December 12, 1998.