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A Macintosh Processor Upgrade (code named STP)[1] is a generic term for a CPU upgrade kit sold by Apple Computer,[2] designed for many Motorola 68040-based Macintosh LC, Performa, and Quadra models. The card contains a PowerPC 601 processor and plugs into the 68040 CPU socket or processor direct slot (PDS) of the upgraded machine.[3] The Processor upgrade card 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 requires and shipped with System 7.5.[4]


Development of the card started in July 1993.[1] 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 slot, due to power used and the space taken by the upgrade, LC cards could not be fitted while the card was installed.[3] This limited the usefulness of the Processor Upgrade Card, as internal ethernet, Apple IIe compatibility, video cards and other LC expansion options must be removed.

3rd party options[]

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.[5] After Daystar went out of business the 100 MHz model was manufactured and sold by Sonnet Technologies as the Sonnet Presto PPC 605.[6]


  1. 1.0 1.1 Somogyi, Stephan. "The PowerPC Macintosh Book - The Inside Story on the New RISC-Based Macintosh", Addison-Wesley, August 1994, pp. 25. 
  2. Macintosh Processor Upgrade Card - Read Me, Apple Inc.[DEAD LINK]
  3. 3.0 3.1 Moran, Tom. "Apple Unveils First PowerPC Product", March 1994, pp. 34–35. 
  4. Macintosh Processor Upgrade - Description[DEAD LINK]
  5. Daystar PowerCard 601, Daystar Technology. Archived 2006-02-18.
  6. PowerPC Upgrades for 68040 Macs with LC PDS by Daniel Knight, Low End Mac. 2016-09-01.

External links[]

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