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slyder

Apollo 1240 conversion to 1260

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Ok. So lets try this blog thingie :)

Inspired by the great work by Stachu I decided to try and upgrade my A1240 board that one of my friends had borrowed and was using. This idea had been brewing in my mind for about a year and I suppose now I could not help it anymore, it had to be realised. My starting situation was this:
[ATTACH=CONFIG]75475[/ATTACH] [ATTACH=CONFIG]75474[/ATTACH]

Began by removing the 68040 CPU with an heat gun and monitoring the temperature of the board. I heated the ceramic side of the CPU only and tried not to heat the board itself too much. In less than ten minutes the temperature was getting close to 200 degrees so I picked up the board and gave it a little tap and the CPU just fell off. That was easy :) Here's the temporary rig I used. My work was being supervised by my boss on the right...
[ATTACH=CONFIG]75476[/ATTACH] [ATTACH=CONFIG]75479[/ATTACH]

Cleaned up all the solder and installed a CPU socket. Installed also pin headers for the voltage converter. Then converter and 68060 in place.
[ATTACH=CONFIG]75478[/ATTACH] [ATTACH=CONFIG]75480[/ATTACH]

Removed the old eprom chip and installed pin headers for a breakout board for bringing the eprom to the top side of the board to allow usage of physically bigger memory modules. Nasty looking thing the first one is :). Here I was preparing for the first test with an MC68EC060 75 Mhz chip. At this point I had the CLKEN resistor in its original place and the CLK jumper in the 060 position. This setup only worked when I put in a 40 Mhz crystal, tested with the ones shown below. Switching the CLKEN resistor to the other position and placing the CLK jumper in the 040 position allowed me to successfully use 60, 66 and 80 Mhz crystals. The XC68060 chip wasn't stable running on 80 Mhz though...
[ATTACH=CONFIG]75481[/ATTACH] [ATTACH=CONFIG]75482[/ATTACH] [ATTACH=CONFIG]75483[/ATTACH]

Decided to test also with the original 68040 bootrom and found out that it worked just the same so there actually is no need to change the bootrom chip. I read the boot code binary off the original chip and it says v5.60 in the binary even though that label said v5.61.
[ATTACH=CONFIG]75484[/ATTACH]

What is left now to do I guess is to try if I can get my 128 MB SIMM to work fully as it now only is shown as 32 MB in the system. Perhaps I'll take a look at the bootrom code and see if there's any way to extend the addressing range. Perhaps I will also look for a rev6 MC68060 for better over clocking.

All in all this was a very interesting and educational project. I learned a lot and had tons of fun...
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Updated 7th September 2014 at 06:39 by slyder

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Comments

  1. jcarvalho's Avatar
    For memory expansion over a total os 64MB in a single chip see this: http://www.amibay.com/showthread.php...mb-single-simm
    It seems that Apollo creators cutted of some tracks on PCB to not address more than 64MB
    Very nice job with the heat gun, I never had the courage to do it
    BTW: tough boss you have!
  2. slyder's Avatar
    Quote Originally Posted by jcarvalho
    For memory expansion over a total os 64MB in a single chip see this: http://www.amibay.com/showthread.php...mb-single-simm
    It seems that Apollo creators cutted of some tracks on PCB to not address more than 64MB
    Very nice job with the heat gun, I never had the courage to do it
    BTW: tough boss you have!
    Thanks for the link for the memory expansion, I hadn't come across that earlier so it is very much appreciated. Today I was actually testing with some assembler code writing around the 32 MB memory boundary while taking some scope shots and couldn't see any action on the SIMM pin-29 which is specified as address line 11. I think I will go through that thread now

    Yeah the heat gun part was initially a bit scary but eventually it was a somewhat slow process so it was quite controllable.. That boss of mine is only four months old and quite tiny but very tough indeed
  3. britlord's Avatar
    What a crappy way to fit the fan. If I may ask...
  4. slyder's Avatar
    Quote Originally Posted by britlord
    What a crappy way to fit the fan. If I may ask...
    Yeah My friend wanted to move the fan so it fits under his Commodore A1200 keyboard. When I was using the card I had no issue with Amiga Technologies A1200 though
  5. slyder's Avatar
    Update:
    I've got this card now running at 100 MHz CPU / 50 MHz memory bus. There's only a minor problem, it stays stable for a couple of hours and then the voltage adapter sort of maxes out. Or may be that there's not enough power throughput via the mother board.

    I'll need to figure out a good solution for providing power to the CPU at 3.3 V. ATX power supplies are a bit too bulky to be use with a desktop A1200.

    All ideas are welcome