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Author Topic: DKB Megachip on A2000: PAL/NTSC issue, help needed  (Read 9224 times)

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Offline Zac67

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Re: DKB Megachip on A2000: PAL/NTSC issue, help needed
« on: September 24, 2005, 02:32:32 PM »
Hmm, I was pretty sure that all square Agnuses 8372 and beyond can do both PAL and NTSC, according to the Test pin (pulled low: NTSC).
My A3k's got an 8372B (318069-03) which BBoA says should be an 8372AB PAL - and I've used it with both PAL and NTSC a lot (both soft- and hardware switched). I guess the info is not very complete...

Denise doesn't care whether NTSC or PAL at all, so that's not it. Probably the Megachip runs specific version only - any jumpers/solder bridges?

After upgrading my old A500 to 1 MB chip back in the golden days, I used a very thin piece of plastic foil to isolate pin 41 (?) to be able to run PAL (later I soldered a wire to the chip and bent the socket pin). Trace J102 to Agnus' socket to make sure it's the right pin. Then check the Megachip to see if it grounds this very pin.
 

Offline Zac67

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Re: DKB Megachip on A2000: PAL/NTSC issue, help needed
« Reply #1 on: September 24, 2005, 06:28:22 PM »
The differences are:
- number of scan lines
- vertical frequency
Running 200 scan lines (NTSC) with PAL frequency results in the 'cinemascope' border at the bottom. Note that these lines are scanned by Denise, but lacking display data they have background color. Software usually checks Vsync to check for NTSC/PAL.

Furthermore, PAL & NTSC Miggys own slightly different clock crystals (NTSC and PAL differ in horizontal frequency), but this only matters for additional video hardware (FF, genlocks, A2024).

Is it possible to open PAL screens when running this involuntary NTSC mode?

BTW: the additional wire is for transmitting the A20 line for addressing the 2nd MB. 68k pin 48 sounds pretty good, but maybe it's not connected on the '030 card in '030 mode. If you own a multimeter you should be able to measure 0 Ohms between the different connection points for the cable.
 

Offline Zac67

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Re: DKB Megachip on A2000: PAL/NTSC issue, help needed
« Reply #2 on: September 25, 2005, 10:02:07 AM »
I'm pretty sure the hardware selection pin is grounded. The Early Startup overrides that, so it works.
 

Offline Zac67

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Re: DKB Megachip on A2000: PAL/NTSC issue, help needed
« Reply #3 on: September 15, 2010, 06:31:43 PM »
According to alexh's extensive studies, you have to stick with the '6-2' code as to which exact Agnus type you have/need. The four digit code + A/B/AB is not exact enough.

There are three different Agnus pinouts (A500/2000, A3000, A500+/600) and you'll have to get the exact type compatible with your chipram extender.

According to alex, 318069-11 is an A500+/600 type as is the 390544-01 - so if it doesn't work it's broken. :(
 

Offline Zac67

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Re: DKB Megachip on A2000: PAL/NTSC issue, help needed
« Reply #4 on: September 15, 2010, 09:35:46 PM »
Quote from: Xanxi;579571
That's really peculiar because the A500 Plus Agnus that didn't work in the Megachip is working fine in the A500 Plus where it belongs :-/


Really strange. However, there have been reports that "A500+"s were produced with an older board rev and 1 Meg Agnus (just Kick 2.0 to justify the "+") - might this be one of those, ie. not capable of 2 Meg chipram? Otherwise I have absolutely no idea, sorry.