This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.
SHH Systeme ( http://www.wbwip.com/shh/ ), a German company, sells the cache upgrade piggyback board in various states of 'do-it-yourself' readiness. The ready-to-go version is $69 (+ $14 S&H). It includes three 32K cache RAMs (62256-15 or equivalent) and can support speed upgrades to 14MHz or better. SHH does not automatically include the firmware ROM. If your firmware version is not v1.7 or v1.8, you will also need to order the v1.8 EPROM which SHH sells for $12. By: Scott G., Andrew Roughan, Rubywand