ACA 1220-25 - showing 18mhz in sysinfo 4.4

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Don't Panic. Please wash hands.

    Hi

    Having purchased a second hand amiga 1200 which i have been using now for a while , i notice it came with a 2012 aca 1220 accelerator card. Looking at the cpu chip the text printed on it confirms it is a 25 mhz version.


    however when i use sysinfo it shows it as 18mhz with 3300 drhystones. I realise sysinfo isnt going to give precise info but 18 mhz seems significant step down. I notice the card itself shows a printed table on the pcb with different clock settings .. could it be that i need to adjust ? I assumed it would by default be at the setting the cpu speed is rated for ?


    any advice welcome

    Thanks

    Tim

    As a side note i have looked at the documentation on the aca tool used for the older cards . I have 3.1 roms so the extra fast ram is auto detected by the os without the need for the tool .


    should i still need to use this tool in startup to activate the 25mhz cpu ? I couldnt see anything about the mhz point specifically in the docs.


    best regards

    Tim

    ACAtool is only for newer cards. The red ACA1220 uses ACAtune with very limited options. Use it to activate MapROM, as this will give a significant speed boost.


    If Sysinfo is showing 18MHz, then the CPU is running at 16MHz. Someone has probably played with the clock multiplier options. Take a look at the top right of the card where the 20MHz crystal is: There's a small 8-pin chip, that's the clock multiplier. Depending on the resistors you assemble there, the main board clock is changed. The logic will derive memory clock and CPU clock from that. If you're unsure, just take a picture of the card, and we'll find a good (over-)clocking setting for that card.


    Jens

    Quote from Tj1978

    interesting that sysinfo recognises the cpu as a 68020 EC variant

    That's a software error - like so many errors in Sysinfo. If it would really be a 68ec020, you would not have 128MBytes of memory.


    Please take a close-up picture of the accelerator, so I can see the CPU and the crystal, but nothing else. You'll probably need a lot more light and the "macro" setting of your camera (which I believe is a phone). Look for a flower symbol, which is often used for macro setting. I can't see enough details on this picture.


    Jens

    Do you think this card came by defualt at 16mhz? Seems odd to underclock a cpu thats rated at 25mhz by the text stamped on the cpu. I can see that the R2 pin has a connection and the others are empty, which tallies up with the table printed on the card for various clocking options..

    I'm pretty sure it came with 25MHz CPU clock and 50MHz RAM clock. I asked you to take a closeup picture with macro functionfor a reason - I want to see the solder spots. However, your last picture still doesn't have the required detail. Please use more light - ideally daylight.


    Jens

    Sysinfo is not very precise in terms of MHz calculation. What does the "WhichAmiga" tool show?


    The jumper setting is correct, as it produces a 50MHz system clock. The CPLD should divide the clock by two. If it doesn't, then the CPU may have been changed at some point and the original frequency of the card may have been 16.67MHz. In that case, you can still change the divider to 2 by closing the "do not close") jumper that is inside the 68030 footprint.


    Jens