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 works with either a 040 or 060 CPU and has 128MB RAM. The card is occasionally available as a fully built card either with or without an 060 on Amibay or on Amiga store – or you can order a PCB and build a card yourself. Read more about the card 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 the openness of the project and the wide user base.
I will now move on to writing about the first out of two cards I built and also my attempt at overclocking it to 100MHz.
There are some parts that are difficult to find if you want to build your own card. That means
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 (anymore), 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 (or cheaper if you go for revision 1 which is perfectly fine in most cases).
An option is to go for the FPU less 68060s, these can be had very cheap. Keep in mind to treat your 060 board as a very fast 030 if you go this route as most 060 programs expect to find a full 68060.
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. Instead I opted to solder the CPU directly to the BFG card, 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. You can actually order KEL connectors from the factory, but you have to order in a higher volume than one or two. So it is not really an impossible to find part, but you wont find it on Mouser or Digikey.
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 main A1200 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 years just marched on and I felt satisfied with the stock speed.
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 this chip.
The main problem was that the rev. 6 68060 CPU was soldered to the Apollo 1260 card, some legs where also snipped off on the bottom of the CPU to not interfere with the 72-pin SIMM memory.
I sent the Apollo card to a electronic repair company to have the 060 CPU professionally desoldered, it was soldered directly to the Apollo card. My hobby grade desolder station could not handle the job and to be honest, I was far too unexperienced in desoldering a part with that many contact points.
So, instead of putting it on a socket on the BFG card I soldered it straight on 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 since some of the pins where shortened down.
So after the BFG 9060 card was built it was time to program the CPLDs and test the card in an Amiga. While it worked fine at 50MHz after first test runs, 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 all day long (and night), 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 set to 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 so it is in reality not that dramatic at all even if it sounds like it.
After I had 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 the famous 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 very 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 when I briefly touched it with my finger.
Even if it felt safe to run without active cooling I thought it would be a wise choice to add a heatsink and fan anyway. To keep the card safe I added a tall heatsink (Enzotech) with a 2 cm tall Noctua 40 mm fan helping to keep 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 very 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 really notice the speed increase?
Yes, I feel that Workbench is more responsive and off course classic 3D games such as AmigaQuake runs and feels much 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