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ACA1221lc (red)
ACA1221lc (blue)

ACA1221lc is an accelerator for the A1200 computer. It is also compatible with the ACA500, ACA500plus and ACA2000. Key features are:

  • processor: MC68ec020 (guaranteed to work reliably up to 26.67MHz)
  • two clock ports
  • up to 11.7 MBytes 32-bit fast RAM (if operated on ACA2000)
  • 1 MByte Maprom option
  • variable clock speed
  • IDE speeder for operation on A1200 computers
  • fully PCMCIA-friendly with all Kickstart versions and all memory enabled


jumper settings

The ACA1221lc comes with the jumper in "park" position. The presence of these jumpers is a leftover from the predecessor card ACA1221ec. All features of the card are controlled with the ACAtool (see further down). Only in emergency cases, you will need to set the jumper to "unprotect", which will let the card start in a safe configuration without overclocking, a low amount of memory and IDE speeder disabled. You will only need this jumper setting if you have saved a configuration that permanently keeps the computer from starting.

The "MapROM" jumper setting is not used. MapROM is controlled by ACAtool.

clock ports

The ACA1221lc features the same two clock ports for adding hardware expansions that the ACA1221ec also had (hence the pictures of the predecessor). 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 (some very early A1200 boards have this problem).

Note that if you want to use the internal and the ACA1221lc 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 ACA1221lc is independent of the internal clock port or 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 plugged directly to the ACA1221lc as shown in the picture. A polarity "nose" helps avoiding connection mistakes. For passing power to RapidRoad, the white power output of the ACA1221lc 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 ACA1221lc is running at 26.67MHz.

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

clocking and overclocking

The ACA1221lc starts up at it's slowest async speed of 20.0MHz. After Autoconfig operations have been completed, the CPU clock will be set to what you have configured, 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.

precise clock rate calculation

The ACA1221lc uses a base clock of 80.0MHz. This clock always drives the SD-RAM controller of the card. Three of the four different CPU clock rates are generated by dividing this clock by the following values:

4: 20.0 MHz

3: 26.67 MHz

2: 40.0 MHz

As a "first" in the A1200 accelerator market, the ACA1221lc introduces the possibility to synchronize the CPU with the A1200 main board (both synchronous and asynchronous clocking unified in a single card). This means that on PAL computers, the card will run at 14.1876MHz, and it will run at 14.31818 MHz on an NTSC A1200. If operated on the ACA500plus, the "sync" speed will be 14.1876MHz, regardless of the A500 video system. This is due to the fact that the ACA500plus is an asynchronous subsystem to the host computer. The ACAtool will only show "14 MHz" as speed setting without actually checking the video system of the host computer. The benefit of having the 68ec020 run synchronously to the A1200 main board is that there will be no extra wait states for accessing chip ram. Games and demos that require full chip ram performance will likely run more smooth than with asynchronous clocking. A famous example is the game "Stunt car racer", which has severe frame rate losses even with very fast 68030 accelerators, but runs smooth if the processor is clocked synchronously.

40MHz overclocking success

The ACA1221lc can be set to 40MHz operation, but this speed is not guaranteed to work in your setup. Always remember that you have bought and paid for a 26.67MHz accelerator. The ACA1221lc is equipped with a small heat sink as standard. This will help dissipate heat and keep the CPU at a low-enough temperature to work at up to 40MHz. However, heat is not the main factor that influences stability at 40MHz. The prime reason why the card may become instable at 40MHz is the power supply. Unfortunately, there are new power supplies on the market that are not suitable for the Amiga (even without accelerator). Our general recommendation is to use the original Commodore power supply. If you are looking for a new PSU, make sure it actually complies with the Commodore specifications, which require cable drop compensation. If you are unsure, please ask the manufacturer of the PSU what type of PSU chassis the product is using; if it's a MeanWell chassis, it's not suitable for the Amiga, as it neither implements cable drop compensation, nor does it have a sense wire option. For stable 40MHz operation, we recommend to set the 5V rail to 5.05V-5.1V, measured at the floppy power connector of the A1200 main board. You should not exceed 5.15V at this measuring spot, and you MUST make sure that the 12V rail stays below 12.5V under all circumstances.


For the ACA1221lc, ACA1221ec and all versions of the ACA1233n, there is a new combined GUI and command line tool available: ACAtool.

Acatool unifies most functionality of the ACA12xx libraries and command line utilities (with the exception of ACAGov) under a single program that can be used from Workbench, command line and startup-sequence alike. It can save the configuration into the ACA1221lc's flash memory, and it lets you activate MapROM, including loading a Kickstart ROM file without losing valuable fast ram. ACAtool also lets you activate the IDE speeder of the ACA1221lc.


The ACA1221lc instruction sheet can be downloaded here: English/German instruction sheet

Hardware Register Documentation is available for developers.

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, ACA1221ec and ACA1221lc 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.

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 129,96 EUR overclocked
ACA1221EC-21.28 4279 (TBD) 9+1+6 MByte 15.2 / 23.1 MB/s 6.1 / 6.9 MB/s no 129,96 EUR
ACA1221EC-28.38 4926 (TBD) 9+1+6 MByte 20.3 / 30.7 MB/s 6.2 / 7.1 MB/s no 129,96 EUR
ACA1221EC-17.03 3416 (TBD) 9+1+6 MByte 12.2 / 18.4 MB/s 4.3 / 4.8 MB/s no 129,96 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
ACA1233n-55 11763 (TBD) 128 MByte 35.2 / 50.2 MB/s 6.4 / 7.1 MB/s yes 379,92 EUR includes A1200 IDE accel
ACA1221LC-20 4015 (TBD) 11.2 MByte 14.4 / 21.7 MB/s 5.9 / 6.9 MB/s no 149,94 EUR includes A1200 IDE accel, starting dec-2019
ACA1221LC-26 5365 (TBD) 11.2 MByte 19.2 / 29.0 MB/s 6.1 / 7.1 MB/s no 149,94 EUR includes A1200 IDE accel, starting dec-2019
ACA1221LC-40 7430 (TBD) 11.2 MByte 26.4 / 43.4 MB/s 6.3 / 7.1 MB/s no 149,94 EUR overclocked, not guaranteed



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