ACA-1231
Amiga 1200 Accelerator Card w/ 68030 CPU incl. MMU. CAn be used with ACA-500 equipped Amiga 500.
Speed:
With its CPU clock speed of 42 MHz* and its on-board memory clock speed of 25 x 3.333 MHz (= 83.325 MHz!), the ACA-1231 plays in the top league of 68030-based accelerator cards.
Memory Aplenty:
The ACA-1231/42 comes with 64 MB RAM, 1 MB of which are reserved to map the Kickstart into the fast memory. With Kickstart 3.1** there are 63 MB FastMem available to applications when you switch the A1200 on (1 MB is always located at address 0x00C00000 to gain compatibility with old or badly programmed software; 62 MB are available en bloque).
On Time:
The ACA-1231/42, unlike its predecessor ACA-1230, always comes with an RTC (Real Time Clock) chip installed. You only have to add a battery.
Hardware Compatibility:
The ACA-1231/42 is more tolerant towards different revisions of the A1200 board than the ACA-1230 was. Immunity against fluctuations of old power supplies has been improved while the power consumption has been reduced.
Software Compatibility:
The ACA-1231/42 sports a fully featured 68030 processor, which also includes a functional MMU (Memory Management Unit). The MMU can not only be used to map a Kickstart ROM image to FastMem, it's also crucial for WHDLoad. The ACA-1231/42 is 100% compatible with WHDLoad! The MapROM function supports Kickstarts of 1 MB size.
* The exact clock speed is 41.6625 (25 x 3.333/2) MHz.
** Kickstart 3.0 users must add the memory with the ACATune software.
Use ACATune tool to configure the ACA1232.
Source: http://www.vesalia.de/e_aca1231-42.htm