Work continues on my Amiga 4000T replica build. On the A4000T a lot of functionality is placed on daughter cards such as audio and video out that is placed on the AV module. The A4000T AV module slots into the Amiga 4000T motherboard in a 40 pin 20 x 2 double row 2.54 mm pin header.
As you can see on the image above, the AV module is about 95% done. It is missing the headphone jack, 20 x 2 double row female connector and two 3904 transistors (and some jumpers).
The BFG9060 is a modern 060 turbo card for big box Amigas. It can take either a 040 or 060 and has 128MB RAM. It is occasionally available as a fully built card either with or without an 060 or you can order a PCB and build a card yourself. Read more about it and who made it here.
I decided to build my two BFG9060 cards myself as I enjoy building hardware and they would compliment my A4000 systems well (that I also built as kits). I have also read a lot about the BFG project and like it! On this page I write about the first card I built and that I tried to overclock to 100MHz.
The most difficult parts to find for the BFG9060 IMHO is the CPU (I thought), the CPU socket and the edge slot (KEL connector). 060 CPUs do not grow on trees, however I still think that they are surprisingly easy to find on the second hand market (in both crippled non FPU versions and full version) and all things considered they can still be had for a reasonable price. The 060 can actually still be found for a relatively ”good” price, between 2-300 euro.
The 68060 CPU socket is difficult to find but not impossible, I got one from a friend in the hobby (as well as the KEL connector) but decided not to use it in this build. I decided to solder the 060s directly to the BFG, more on that later. The KEL connector is difficult to find but there are some builders of these cards that might have a spare one to sell. Keep in mind that the CPLDs are EOL and will be difficult to find in the future (for a good price). Other than that its mostly a straight forward build.
I have an old Apollo 1260 that I got for a great price back in 2008. I have been running it in my old A1200 at 50MHz and it has been great during those years, I love an 060 in an Amiga, makes the whole system much more fun to use.
The Apollo card had a rev. 6 68060 on it which the seller claimed could easely do 75MHz when he sold it to me. I never tried overclocking on the Apollo turbo card but thought that some day I would, that never happened though. Since the BFG9060 supported a 100 MHz overclock I thought it was an excellent idea trying the CPU on that card instead and finally find out how much I could push the chip.
I sent the Apollo card to a guy who could professionally desolder the 060 CPU, it was soldered directly to the Apollo card. My hobby grade desolder station could not handle the job.
Instead of putting it on a socket on the BFG card I decided to solder it directly to the card once I got it back. It would have taken a lot of time to clean and straighten the legs out to get it to fit a socket if it was possible at all.
So after the card was built it was time to program the CPLDs and test the card in an Amiga. While it worked fine at 50MHz I was sure I wanted to try to get it running at 100MHz.
The later revision of the 68060 (71E41J) is famous for being able to be overclocked and running happily at 100MHz or more, the BFG only supports up to 100MHz though, but a 50% overclock was fine for me!
It is here I found a problem. The card refused to start when jumpered to 100MHz. I could feel the CPU getting warm but my A4000TX never booted to Workbench. However, I could get into the early startup menu with the BFG at 100MHz – That was promising!
Turned out I had to overvolt the card slightly by replacing a resistor that increased the voltage for the CPU. Keep in mind this was still in line within the specifications of the 68060 even when overvolting the card. After I replaced the resistor R9 with a 2.87K resistor, bumping voltage up from 3.3V to 3.4V, the BFG9060 happily booted at 100MHz and ran stable playing Quake demo for hours!
So on the BFG9060 the resistor R9 controls the output of the voltage regulator, acording to the info I got the corresponding resistance of the resistor on the left side below would correlate to the voltage on the right side below:
I was initially worried I would be running the card hot when it was overclocked, but that proved to be false. I dont have any data, but the turbo card and the CPU did not feel hot at all. But to keep the card safe I added a tall heatsink (Enzotech) with a 2 cm tall Noctua 40 mm fan keeping the CPU cool. I have forgotten the exact part number for this cooler but it fits the 060 as a glove and clips on the CPU. The two CPLDs got black heatsinks attached with thermal conductive tape (after I took the pictures below). I am running this card in my A4000TX that is installed in a tower, it has a 120 mm Noctua fan blowing in from the front. The whole system runs cool!
My overclocked card has been stable for more than a year (as has the Amiga it is running in). My A4000TX is a dream to use at 100MHz together with a zz9000 graphics card. Do you notice the speed increase? Yes, I feel that Workbench is more responsive and off course classic 3D games such as AmigaQuake runs faster at 100MHz. I have not had a single crash that could be attributed to the CPU card (in either overclocked or non overclocked state) which proves (for me) that the BFG in my A4000 is a very stable and dependable CPU card. Great job everyone involved in making this card and who decided to release it open for anyone to build!
There is an excellent documentation of the BFG9060 card here