| [Prometheus](https://rusefi.com/forum/viewtopic.php?f=4&t=1215) | + The only rusEfi board with on-board wide band controller.<br/>+ compact 4-layer PCB smaller than 93 x 100 mm<br/>+ on-board power supply<br/>+ knock sensor chip<br/>+ stepper motor IAC controller chip<br/>+ stepper motor IAC controller chip<br/>+ onboard 4-channel "smart" protected ignition drivers<br/>+ bluetooth module<br/>+ supports two packages of on-board stm32 chips | no on-board connector (wired)<br/>SD card, USB/TTL, CAN | 2017 | 4 cylinder. No plans to offer assembled units. |
| [Frankenstein](https://rusefi.com/forum/viewtopic.php?f=4&t=359) | + Simplest rusEfi board<br/>+ our smaller two-layer board<br/>+ Small Box shipping rate<br/>+ low price<br/>- external 5v power supply required<br/>- external brain board required | no on-board connector (wired)<br/>SD card, USB/TTL, CAN<br/>open source hardware | 2014 | Flexible - probably 8 cylinder max recommended. No plans to offer assembled units. |
| [microRusEfi](Hardware-microRusEfi) | + Available fully assembled!<br/>+ about 10 analog inputs<br/>+ One VR/Hall input channel for crank sensor<br/>+ One Hall input channel for crank sensor<br/>+ 4 injector output channels<br/>+ 4 logic level coil control channels (external igniters could be needed for some coils) | 48-pin connector<br/>On-board DBW<br/>USB, CAN<br/>open source hardware | 2019 | 4 cylinder, single electronic throttle |
A: rusEFI preference at the moment is KiCad 5. A few legacy pieces are still using KiCad 4. While many EDAs have many cool features KiCad gives rusEFI uniformity and consistency.
A: There is no single right answer. It really depends on what kind of electrical signal is your tachometer expecting. Is it low-side driven? +5v logic signal driven? +12v logic signal driven?