JiffyDOS ROM for Commodore 64 (switchable) - CustomCommodores is an authorized reseller for JiffyDOS (See go4retro) 

The adapter is 101% designed, fabricated, built, and shipped from the USA

I wanted to design a cool looking, quality made yet simple adapter for the M27C128 ROM (28 pin) to adapt to the C64 Breadbin 24 pin socket. This rom is NOT for the newer C64C short board.

**MUST have corresponding drive JiffyDOS to enable full is a Disk Operating System (DOS) enhancement which gives

your C-64 or C-128 the disk access speed it has always needed. A

chip-for-chip replacement for the Kernal ROM in your computer and the

DOS ROM in your disk drive(s), JiffyDOS achieves levels of performance

and compatibility unmatched by other disk speed-enhancement products.

Outstanding speed, solid compatibility with virtually all hardware and

software, and a new set of desperately-needed commands and features,

gives your system a new lease on life and the power to compete with

today's newer, more-expensive machines.

JiffyDOS should not be

confused with Cartridges, Turbo ROMs, Burst ROMs or "Parallel" systems.

Ultra-high-speed multi-line serial technology enables JiffyDOS to

outperform these products without any of their inherent disadvantages.

JiffyDOS leaves all ports on your computer open, works with virtually

all software, speeds up PRG, SEQ, REL and USR files, and does not

require any extra cabling. Owning JiffyDOS also gives you access to some

of the best product support available.

I will send a link to the instruction manual once you have purchased the ROM chip via messages. 

This product is the actual ROM IC that replaces the DOS or KERNAL ROM

IC in your CBM unit.  The unit comes preprogrammed with the correct

version of JiffyDOS.