The IFEL ARM3 36MHz processor upgrade is the fastest of all the ARM3 processor upgrades available for the Archimedes range of machines. It takes the raw throughput of the processor up to 17.44 MIPS. For comparison the ARM2 processor achieves around 4.85 MIPS in the same machine and an ARM3 25MHz processor achieves 12.72 MIPS. An A400/1 series machine with a 36MHz ARM processor matches an A5000 Alpha which has a 33MHz ARM3 processor and 12MHz memory bus. According to some, only 400 of the 36MHz ARM3 chips were ever produced for an Acorn project that didn't happen and so the processors found their way into third party upgrades such as this one.
As you can see from the photo, the ARM3 daughterboard has the circuitry to support the IFEL FPA upgrade that was designed but never produced.