Clarify FPU install on ACA1234 /w CPLD v3

lowlytech · Dec 27th 2021

Thanks Jen for this great hardware, got the cable in and the CPLD update fired off without a hitch first try.

Before I started to install my FPU, I wanted to confirm that I need to cut the B4 pin from my 68882 socket off completely before soldering down the socket, and then run a patch from the CPU to the B4 position for the cache function option.

Additionally on the 2 SMD components I need to attach for the FPU, are both the DIV2 and the clock speed positions 33ohm resistors? I can see the clock speed obviously is, but I wanted to confirm the DIV2 was as well.

Thanks again.

OMo1972 · Dec 27th 2021

Both are 33 Ohm resistors.

See:

http://wiki.icomp.de/wiki/ACA1234

lowlytech · Dec 28th 2021

Thanks, just wanted to make sure since it said to use only one resistor. What about the FPU socket pin since the V3 update? Good to just cut the pin in question off the socket?

lowlytech · Dec 28th 2021

Looks like this post on the German side answered my question

https://forum.icomp.de/index.php?thread/2317-aca1234-cpld-v3-update-fpu/

Jens · Dec 28th 2021

Right - the FPU pin itself may not have any connection to the B4 position. Originally, this is meant to identify presence of the chip. The new CPLD code now detects the FPU in a different way, giving way for a new signal to enter the CPLD on this pin.

The CPLD code will work with and without wire link, and it will work with and without the FPU having a connection to the B4 position. However, it will not work if wire link and FPU pin are shorted, hence the requirement to remove the pin from the socket.

Once again, I do not recommend using an FPU at all. I currenty don't know a "killer application" for the FPU.

lowlytech · Dec 29th 2021

Thanks Jens for the reassurance on the install of the FPU. I understand it isn't recommended, my main reason for installing is my old Microbotics accelerator had an FPU so I was constantly getting FPU related errors since it wasn't present with the ACA1234, and I am not versed enough with Amiga to remove the dependency for the FPU.

On a positive note, got the one socket pin removed, and soldered in, installed the link wire and everything seems happy as the card/system detects the FPU @ 50Mhz and not getting anymore crashes due to lack of FPU.

Very cool card, I appreciate you working so hard and pouring your soul into your products. Very happy customer here in the US.

Thanks and have a great New Year.