The MiSCUSI "Minifies" the Apple II SCSI Card with a Swap to Surface-Mount Technology
Two-layer board drops the footprint without making it expensive to have produced at a factory.
Pseudonymous maker "hkz" has released a redesign of Apple's Small Computer System Interface (SCSI) card for the Apple II family of microcomputers — with a "minified" footprint shrunk through the use of surface-mount components: the MiSCUSI, or "Mini SCSI Card Uselessly Sitting Idle."
"The MiSCUSI is a re-implementation of the Apple II SCSI card, built after a fortuitous recovery of the PLD [Programmable Logic Device] dumps from a forum post," hkz explains of the new board for a classic computer. "It's a double sided PCB, most of the components are SMD [Surface-Mount Devices] and all are placed on a single side, with the explicit intent of making this board small and easy/cheap to build in a factory."
The Apple II, officially trademarked as "Apple ][" before an angular shift to "Apple //," was launched in 1977 as a successor to the limited-run Apple Computer 1 that launched the company. Built around a MOS 6502 processor, the machine offered improved expandability over its predecessor and proved popular enough that the family wouldn't be discontinued until 1993 — a decade after the launch of its successor the Apple Lisa and nine years after the Lisa's own successor, the Apple Macintosh, came out.
Apple itself launched a range of expansion cards for the Apple II, including one designed around the Small Computer System Interface (SCSI) — originally launched in order to support the Apple Hard Disk 20SC storage add-on, but capable of connecting to up to seven SCSI devices simultaneously. Today the original Apple II SCSI Card is hard to find, but one owner succeeded in dumping the configuration of its on-board Programmable Logic Devices (PLDs) — making it possible to build clones.
The MiSCUSI takes Apple's original design and swaps out the classic components for surface-mount versions, solving both availability issues for a decades-old bill of material while also considerably shrinking the footprint of the card. It also includes a tweak over Apple's original version: an on-board active termination circuit, "optional," hkz notes, "and can be disabled by pulling two resistor networks."
The KiCad project files, production Gerbers, and PLD/ROM files are all available on Codeberg under an unspecified license; "any use of this project is under your own responsibility," its creator notes. "You will be responsible of checking the correct construction and functionality of your board. By using this project You will agree that I cannot be held responsible if it will destroy any of your devices, damage your computer, burn down your house or whatever."