MK2cr - best driver / mode?

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Don't Panic. Please wash hands.
  • Really enjoying my Indi MK2cr, but right now I'm running it at PAL Laced, because my Lisa doesn't like getting a good workout - HighGFX at 1024x768 for example starts showing artifacts after few minutes. I think ideally I would like to run 800x600, and was wondering, what's the best driver for that, especially looking at minimizing the load on Lisa. Also, are there any recommended solutions for cooling it down?

  • That $FEFEFE colour trick may not fix all problems that an A1200 may have when using S-Hires/Double-CAS modes. bitter, that's definitely not Lisa "not liking the workout", but a plain assembly error that was made by whoever produced the A1200 back in the days. There is a number of memos from Commodore on the topic of timing fixes, but none of them is really complete.

    I did some research myself to find&fix the errors. If you have SMD soldering equipment, you can make your A1200 compatible with S-Hires modes:

    1) The negative bias voltage of the Alice-chip is already supported with a ceramic capacitor, but that's too small. I'm talking about C2X on the bottom side of the A1200 board, about "under Alice". You just add a 10µF ceramic cap on top (no need to remove the old one).

    2) The CCK clock needs to be delayed a bit, which can be done with a 100pF capaitor to Vcc. Indivision AGA MK2 is prepared for such a modification: You can just solder the 100pF cap onto the unpopulated place R24. However, that's probably the only part of your setup that's still in the warranty period, so you might want to choose any other place on the A1200 board where CCK and Vcc are close to each other.

  • It is likely that the A4000T benefits from similar chipset fixes, yes. Since these computers were developed at a time when monitors for SHires were just not around, you have to keep in the back of your head that even the developers of these computers did not have a chance to give these screenmodes a full test run.

  • Is there a possibility this will be compensated for in the MK3?

    The prototype of the MK3 version (which is now in the making - I took all components to the assembly place today) does have switchable capacitors and pull-up resistors on critical lines, so the amount of soldering is smaller. However, the capacitor on Vbb (the negative bias voltage of Alice) can't be reached from the Lisa socket, so not everything can be compensated for on the MK3.

  • how soon will you be able to share information about the MK3?

    My hope is that this prototype will be assembled before Xmas, so very basic tests (like configuring the FPGA, output a test picture) can be performed before the end of the year. However, there are other features that need software and FPGA core development before we can publish their functionality. Please understand that development can also mean that an idea does not work out in practise, and I really don't like to promise things that in the end can't be kept.

  • The last reply was more than 365 days ago, this thread is most likely obsolete. It is recommended to create a new thread instead.