ACA1233 FPU capability

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Don't Panic. Please wash hands.
  • I can see there is a FPU PGA socket on the board but can see no mention of populating it with a FPU and I assume the the correct speed oscillator module.

    Is there any documentation that describes how to add an FPU?


  • The basic ability to sense an FPU and use it is in every ACA1233 and ACA1233n. However, there is no official support for that. Feel free to install the socket and add a clock (either by installing an oscillator or by closing the solder-jumper if the FPU shall run at the same speed as the CPU).

    If you do this, you're on your own. My personal recommendation is to not use an FPU, as hardly any software really requires it. On the other hand, there are tons of fake FPUs on the market, and it is *very* hard to identify them. Sometimes it's as easy as "68881 has been re-labelled to 68882-50" (which is quickly identified with the "CPU" command of every WB installation), but if "CPU" is showing a 68882, you might need several months to find out that it's been re-labelled with the wrong (higher) speed, as failure of these chips only shows in rare cases. Other effects may be that the bus load on the card is increased, and RAM data may not arrive in time at the CPU - random crashes may result if you happen to install an FPU with an older mask set. You might need to disable burst in such a case, which reduces the overall system performance.

    I don't think that the small percentage of programs that benefit from an FPU is worth all the risk and instability. In terms of warranty, there is no "risk", but a certainty: If you solder in the card, your warranty will be void. Operating the ACA1233 or ACA1233n with an FPU is outside advertised parameters.

  • Hi,

    Where is this jumper mentioned in "closing the solder-jumper if the FPU shall run at the same speed as the CPU"?

    I will be very much grateful if someone can reply please.