I have an ACA1221 accelerator (not EC). The card is clocked at 28MHz and get's VERY hot. Even when running on default 17MHz the temperature can go as high as 65'C. Is there any way to use any of the cards connectors to install some kind of fan?

1 Answer 1


The manufacturer's wiki shows that the ACA1221 provides a port to supply power to the RapidRoad USB accessory through a simple jumper cable. From the end of the third paragraph in the Clock Ports section of the ACA1221 wiki page:

For passing power to RapidRoad, the white power output of the ACA1221 can be used.

The RapidRoad's power connector is wired to be powered from either the ACA1221's power port or a standard floppy drive power plug, as stated in the final sentence of the Overview section of the RapidRoad's wiki page:

The high-current switch can supply up to 1.5A of power per port. For this high power rating, separate power must be supplied through a 3.5-inch floppy power connector.

This would imply that the power output connector of the ACA1221 shares the same pinout as a floppy drive connector and can provide at least 3 Amps of current on the 5 Volt pin, and also that the 5 Volts available on the Clock Port is not able to supply 3 Amps of current. The pinout could be easily verified using a digital multimeter.

Edit: After close inspection of a random web image of the back of the ACA1221, it appears as if I can make out a ring around the 12 Volt pin of the power connector, so at least it is not connected to the ground plane, and may very well have the 12 Volts routed through from the Zorro bus connector:

enter image description here

  • Is that a +5V only power output? Many fans won't spin up reliably on 5 volts.
    – mnem
    Commented Jul 22, 2019 at 0:22
  • 1
    @mnem - While 12 Volts is available on the Zorro connector, I cannot find any information to verify if it is routed to the power connector, as the connector is intended specifically for use by the RapidRoad accessory and the RapidRoad does not appear to need a 12 Volt source. They may have routed it through though, just in case they later developed another clock port accessory that did require 12 Volts. Whether this is true or not would have to be checked by close visual inspection and/or by testing, as stated in the last sentence in my answer.
    – Hitek
    Commented Jul 22, 2019 at 0:30
  • @mnem - Also I should note that many high speed 12 Volt fans run quite well and much quieter at 5 Volts. If a specific 12 Volt fan were required to be used that didn't perform reliably on 5 Volts, an inexpensive 5 Volt to 12 Volt Boost Converter could be used. Conversely, 5 Volt fans of many types and sizes are quite easy to source.
    – Hitek
    Commented Jul 22, 2019 at 0:33

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