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ACA1221 is an accelerator for the A1200 computer. It is also compatible with the ACA500 and ACA500plus. Key features are:

  • processor: MC68020-16
  • two clock ports
  • 9 MBytes 32-bit fast RAM (expandable to 63MByte)
  • Maprom option
  • variable clock speed


jumper settings

Before you install your card, you should check that the jumper is in "idle" or "park" position. It may have been left in "trial" position after quality control, and you may lose valuable trial runs with full licensing if you keep it in that position.

In jumper position "trial", all features of the card will be unlocked. The computer can be started in this configuration up to ten times - the ACA1221 will count power cycles, not resets. You can run the computer for an unlimited time and reset it as often as you want. The numer of trial runs left is only decremented on power cycles.

Jumper position "unprotect" is only required for adding or removing a license. You may need to bend the jumper pins up in order to fit the jumper in this position.

clock ports

ACA1221 with expansions

The ACA1221 features two clock ports for adding hardware expansions. The first clock port is mainly meant for an RTC module. As opposed to earlier accelerators with an RTC port, this port is a straight copy of the internal clock port of the A1200. That means you can also use it to connect a Catweasel MK2, Silversurfer or Delfina card. In that case, the internal clock port of the A1200 may not be used for such an expansion, but can be used for an RTC module. This male clock port is extremely useful if you own an early A1200 mainboard that has the clock port assembled in the wrong position.

Note that if you want to use the internal and the ACA1221 male clock port at the same time, you may only use one RTC module and one clock port expansion card, but you can never use two RTC modules or two clock port expansions at the same time.

The second clock port of the ACA1221 is independent of the internal clock port of the male clock port. This means it can be used in addition to any clock port device and/or RTC that occupies the other clock ports. The female clock port has been designed for the RapidRoad USB host controller. A clock port cable is not required; the card must be pluged directly to the ACA1221 as shown in the picture. A polarity "nose" helps avoiding connection mistakes. For passing power to RapidRoad, the white power output of the ACA1221 can be used.

If you already have a RapidRoad inside your A1200, we recommend to use this dedicated port instead, as it is considerably faster than the "normal" clock port: You will get over 1MByte/s performance from USB mass storage devices, if the highest overclocking rate of the ACA1221 is enabled.

The second "female" clock port uses memory address 0x00d90001.

startup behaviour

The ACA1221 may start up with a red screen in some cases. This may happen on a cold-start or after a reset. This is not an issue, as it will not keep the system from starting at all; it's just a property of the card with certain A1200 motherboard revisions, and it's perfectly normal behaviour.

clocking and overclocking

The ACA1221 starts up at it's slowest speed of 9.46MHz. After Autoconfig operations have been completed, the CPU clock will be increased to 17.03MHz, and caches will be enabled. This has been implemented in order to give harddrives enough time to spin up and be available after a cold-start, even under Kickstart 3.0. If you have purchased an overclocking license, you can set 21.28 or even 28.38MHz clock speeds. Please use the ACAclock tool to set the speed, or the ACAgov CPU governor to automatically set the CPU speed according to CPU speed requirements

precise clock rate calculation

The ACA1221 uses a base clock of 85.12548MHz. This clock always drives the SD-RAM controller of the card. The four different CPU clock rates are generated by dividing this clock by the following values:

9: 9.45838 MHz

5: 17.025096 MHz

4: 21.28137 MHz

3: 28.37516 MHz

Please note that although the highest frequency may look like the card is clocked syncronously to the A1200 mainboard (because it's the same as the chipset base frequency), the two clocks are not syncronized at all. The ACA1221 is a purely asyncronous card, and will run at the exact given frequencies, even if the host computer is an NTSC version, which is usually clocked at 28.63636 MHz.


LHA archive containing ACA1221 library, ACAControl, ACAgov and ACAclock

Licensing operations

All licensing is controlled with the ACAcontrol commandline tool. It is contained in the above LHA archive. To purchase licenses, you need to know the warranty ID of your card. You can find it in three places: On the card itself; the silver sticker shows the 5-character warranty code. On the retail box: The white sticker on the right side of the box shows the same code. By starting ACAcontrol without any arguments: The warranty ID of the card will be shown as "Serial". The warranty ID is case-sensitive, that means a capital letter is different from a lower-case letter. There may be special characters in the code - just make sure that you get all five characters of the code right, otherwise we cannot sell you any license!

For any licensing to be changed, the jumper must be put into position "unprotect". If you just want to display the licenses that have been installed for your card, use this command:

ACAControl L

This will display a list of purchased licenses.

Adding a license

Licenses can be purchased in the iComp online shop only. They are not available anywhere else. All licenses are stored permanently in your ACA1221, so it will survive a reboot or a power cycle. To add a license, the jumper must be set to setting "unprotect", otherwise the non-volatile storage of your ACA1221 card is write-protected and changes to licensing are inhibited.


If your card has warranty ID MTje4, and you have purchased the MapROM option, the code you have gotten would be:


To add this code to your card, enter the command line:

ACAControl A u4FIGKat2K0x65m

After you have entered this line, the license is immediately available, and MapROM can be activated using the ACATune tool V1.9 or higher. The same applies to overclocking licenses, but for memory licenses, a re-start of the computer is required.

Refunding a license

Some license codes can be refunded. If for example you have purchased an overclocking license, and found that your card is instable with it, you can request a refund from iComp. You will then get an eMail with the refund code that you need to enter using this option.


Let`s assume that your card has warranty ID MTje4, and you have found that your card is not stable at 28.38MHz, you request a refund by eMailing us. You will then get this refund code via eMail:


Enter this code with the following command line:

ACAControl R 1jDGmQKf1hnFAs

You will then be prompted to confirm the refund, because this is a permanent operation that cannot be reversed. After you have confirmed the action, the 28MHz overclocking feature will be disabled, and you will see the following confirmation code:


Now you can e-Mail this code back to iComp. Once we have recieved this code, we have a confirmation that the 28MHz option is switched off, and your money can be refunded.


The ACA1221 instruction sheet can be downloaded here: English/German instruction sheet

possible required board modifications

Commodore and Escom have made all kinds of mistakes when assembling A1200 motherboards. Internal memos from Commodore are available that clearly say to remove capacitors E123C and E125C for any version of the Budgie chip, yet, you can find lots of boards out there that have these capacitors assembled. Less often, but at least as severe, some boards have capacitors E121C and E122C assembled. This will harm the quality of the 14MHz board clock to a degree where most accelerators (not just ours!) become instable.

You cannot tell from the board revision or the year of your board if the capacitors have been assembled, as practically all revisions have been assembled with all combinations of chipsets and timing fixes (required or not). Your only chance is to check your individual board and remove the capacitors if they are there. There is no reason for these parts to be assembled, other than some Commodore employee's excuse about not getting the memo.

Only our latest accelerators ACA1233n and ACA1221ec have implemented special logic that can handle most of the timing errors caused by wrong assembly of the A1200 main board. These cards may work reliably, although the mentioned capacitors are installed. We still recommend to remove the capacitors, as they have other negative effects, too.

42.56MHz overdrive mode

This mode will only work with ACA1221 revision 1.3 or higher. The ACAcontrol tool will output the version number if called without any arguments. Further, the new logic revision can also be seen on the serial number displayed in the autoconfig structure: V1.3 cards have serial number 2, while previous cards have serial number 1.

Only very few CPUs really work at 42MHz. Check the CPU mask before trying the hack or even buying the CPLD update: The CPU mask revision can be read in the second line, right under the CPU type number. Only mask revisions E30G and C54S are known to work at 42MHz. Mask revision C10H will only work up to 28MHz, and mask revision B47K will only work up to 21MHz.

To activate 42MHz mode, both jumpers must be closed at the same time. This seems physically impossible, because they share the middle pin. You must therefore create a jumper that connects all three pins, or connect them by other means, where soldering is not recommended. Please note that connecting all 3 pins together will also enable "trial mode", so trials will be counted on every startup. However, the card will appear as if the "unprotect" jumper is not set, so licensing operations are not possible.

To enter 42MHz operation, 63MBytes must be licensed and MapROM must be activated. In this state, the 28MHz setting is converted to 42MHz.

ACA 12xx Benchmarks

Benchmarks are measured with AIBB and the popular Sysinfo tool. While AIBB gives detailed information about the performance in specialized cases, Sysinfo will only give you a rough estimation of the performance you can get. We recommend to download the AIBB modules and compare the specific test results against your machine - this will give you much more information about a certain strength or weakness of the card you're comparing. Fastmem performance is measured with the freely available tool "Bustest". Only the "read multiple" and "write multiple" values are given here. Results may vary slightly due to cache alignment differencies.

Product name Sysinfo Dhrystones AIBB module download Fastmem included Fastmem performance r/w Chipmem performance r/w MMU retail price incl. VAT comment
ACA1220-16 3320 media:AIBB_ACA1220-16.LHA 128 MByte 11.8 / 17.7 MB/s 4.2 / 4.5 MB/s no -,-- discontinued per apr-2014
ACA1220-20 3998 media:AIBB_ACA1220-20.LHA 128 MByte 14.2 / 21.3 MB/s 4.7 / 5.1 MB/s no 104,90 EUR
ACA1220-25 4266 media:AIBB_ACA1220-25.LHA 128 MByte 17.6 / 21.4 MB/s 6.1 / 7.0 MB/s no 114,90 EUR
ACA1220-33 5712 media:AIBB_ACA1220-33.LHA 128 MByte 23.6 / 28.8 MB/s 6.3 / 7.0 MB/s no 129,90 EUR
ACA1220-40 6867 (n/a) 128 MByte 28.3 / 34.5 MB/s 6.4 / 7.0 MB/s no -,-- EUR not officially sold (overclocked)
ACA1232-20 4553 (n/a) 128 MByte 13.3 / 21.3 MB/s (not tested) yes 124,90 EUR
ACA1232-25ec 5708 media:AIBB_ACA1232-25.LHA 128 MByte 16.6 / 26.7 MB/s (not tested) no 119,90 EUR
ACA1232-25 5708 media:AIBB_ACA1232-25.LHA 128 MByte 16.6 / 26.7 MB/s (not tested) yes 134,90 EUR
ACA1232-33 7529 media:AIBB_ACA1232-33.LHA 128 MByte 22.2 / 35.7 MB/s 6.2 / 7.0 MB/s yes 154,90 EUR
ACA1232-40ec 9045 media:AIBB_ACA1232-40.LHA 128 MByte 26.7 / 42.9 MB/s 6.4 / 7.0 MB/s no 159,90 EUR
ACA1232-40 9045 media:AIBB_ACA1232-40.LHA 128 MByte 26.7 / 42.9 MB/s 6.4 / 7.0 MB/s yes 184,90 EUR
ACA1233-40 9045 media:AIBB_ACA1232-40.LHA 128 MByte 26.7 / 42.9 MB/s 6.4 / 7.0 MB/s yes 199,92 EUR
ACA1232-50 10576 media:AIBB_ACA1232-50.lha 128 MByte 29.3 / 43.6 MB/s 6.4 / 7.1 MB/s yes 299,94 EUR limited edition, starting mid-November 2015
ACA1233-55 11747 media:AIBB_ACA1233-55.lha 128 MByte 32.6 / 48.4 MB/s 6.4 / 7.1 MB/s yes 359,94 EUR limited edition, starting mid-November 2015
ACA1221-9.46 1878 media:AIBB_ACA1221-9.lha 9-63 MByte 6.7 / 10.1 MB/s 3.4 / 3.9 MB/s no 79,98 EUR under-clocked
ACA1221-17.03 3408 media:AIBB_ACA1221-17.lha 9-63 MByte 12.1 / 18.4 MB/s 4.8 / 5.4 MB/s no 79,98 EUR
ACA1221-21.28 4266 media:AIBB_ACA1221-21.lha 9-63 MByte 15.2 / 23.0 MB/s 6.1 / 6.9 MB/s no 79,98 EUR overclock option 5,- EUR
ACA1221-28.38 4914 media:AIBB_ACA1221-28.lha 9-63 MByte 20.2 / 30.7 MB/s 6.2 / 7.1 MB/s no 79,98 EUR overclock option 15,- EUR
ACA1221EC-42.56 6401 (TBD) 9+1+6 MByte 25.8 / 37.1 MB/s 6.4 / 7.0 MB/s no 119,94 EUR overclocked
ACA1221EC-21.28 4279 (TBD) 9+1+6 MByte 15.2 / 23.1 MB/s 6.1 / 6.9 MB/s no 119,94 EUR
ACA1221EC-28.38 4926 (TBD) 9+1+6 MByte 20.3 / 30.7 MB/s 6.2 / 7.1 MB/s no 119,94 EUR
ACA1221EC-17.03 3416 (TBD) 9+1+6 MByte 12.2 / 18.4 MB/s 4.3 / 4.8 MB/s no 119,94 EUR
ACA1233n-26.67 6031 media:AIBB_ACA1233n26.lha 128 MByte 19.2 / 38.2 MB/s 6.1 / 7.1 MB/s yes 169,92 EUR
ACA1233n-40 9203 media:AIBB_ACA1233n40.lha 128 MByte 28.8 / 57.4 MB/s 6.4 / 7.1 MB/s yes 239,94 EUR



If possible, please shop locally. This product is available only from resellers who have supported this development. Please note that license codes are not reseller items - they must be purchased from our web shop.

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