Macintosh Processor Upgrade

Macintosh Processor Upgrade cards (codenamed STP) are CPU upgrade cards marketed by Apple Computer for many Motorola 68040-powered Macintosh LC, Quadra and Performa models. The card consists of a PowerPC 601 CPU on a small circuit board that plugs into the 68040 socket or processor direct slot of the computer to be upgraded. Some upgrade cards required the original CPU be plugged back into the card itself, and gave the machine the ability to run in its original 68040 configuration, or through the use of a software configuration utility allowed booting as a PowerPC 601 computer running at twice the original speed in MHz (50 MHz or 66 MHz) with 32 KB of L1 Cache, 256 KB of L2 Cache and a PowerPC floating-point unit available to software. The Macintosh Processor Upgrade shipped with System 7.5, which was required to support the card.

History
Development of the card started in July 1993. The upgrade card was announced in January 1994 at the Macworld Expo in San Francisco. Apple described the Macintosh Processor Upgrade Card as giving a performance increase of "two to four times" for general purposes, or "up to 10 times" for floating-point intensive programs.

While the Macintosh Processor Upgrade did not plug into the LC processor direct slot, due to power used and the space taken by the upgrade, LC PDS cards could not be fitted while the card was installed. This limited the usefulness of the Processor Upgrade Card, as internal ethernet, Apple IIe compatibility, video cards and other LC PDS expansion options must be removed.

DayStar Digital manufactured the Macintosh Processor Upgrade Card for Apple, sold the same card as their Daystar PowerCard 601-50/66 and also manufactured a Daystar PowerCard 601/100 which reached 100 MHz. After Daystar went out of business the 100 MHz model was manufactured and sold by Sonnet Technologies as the Sonnet Presto PPC 601.