A500 runs faster than normal, it is a NTSC?

mariosMSX

mariosMSX

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I just realized that one of my A500, have a strange behavior... it runs faster than the normal A500. I have noticed that in some games, but when i placed the disks with pinball Dreams, the game was completely different, due to increased speed. I have also noticed that the screen is "pushed" in lower position in TV, i use a RGB-scart cable. The "flippers" in Pinball Dreams was about 20cm lower, so it was hardly to see them.
Almost every game runs in higher speed.

Is this a NTSC A500? how can i notice if it is NTSC? all the NTSC A500 runs faster? i have placed a +1,5 MB expansion (with gary adapter) nothing else. Could the Agnus chip been changed by previous owner?
 
Hmm. Try running the WhichAmiga utility, it should be able to detect your Agnus version IIRC. And post back the results (y)
 
The agnus chip writes
8370
3087 23

is this logical to A500 rev 6A ? i suppose that rev 6A have agnus 8372 and later.
Only the agnus chip is responsible for NTSC/PAL ? replacing the agnus with a 8372A will change the A500 to a PAL model?
 
That is indeed NTSC Agnus. From Rev 5? Wikipedia snip:

8370 (PLCC) - Amiga 500 to Rev 5.x (NTSC); Amiga 2000 model B to Rev 4.5 (NTSC)

I think you can switch to PAL mode with software somehow. Might be worth a try.
 
Ι have an Agnus 8372A for spare, if i place that Agnus, the A500 will become a PAL one?
There is a "sign" or something so someone could identify if an A500 is PAL or NTSC ?
 
I would check if they have the same pinout and are compatible before attempting something like that.

Which Kickstart ROM does it have? I assume 1.3, but if you had 2.x you can switch PAL/NTSC in the early bootup menu.

My suggestion is, try switching to PAL in software first to see if that solves your problems.
 
just run sysinfo it will tell you if the machine is ntsc or not:)
 
You'll have to change more than the Agnus to convert from NTSC to PAL. There is an oscillator (X1) which produces the video frequency. On a PAL system, this oscillator will have the value 28.37.... on an NTSC machine it should be 28.63....
You'll also have to switch JP4 to select which video mode is used.

Bryce.
 
@ Bruse : the crystal is 28.37516MHZ, so it is a PAL A500 with a NTSC agnus. Someone has change it. JP4 is closed, soldered.

@ velourfog : i think that it is easy to change the ROM chip (1.3) with the 2.04 ROM chip and select the PAL/NTSC mode. The ROM chip is on socket, it is easier than the Agnus chip, that could probably broke some pin while removing.
 
@velourfog
The 8370 Agnus is "NTSC" fixed. The 8371 is "PAL" fixed. They're not software switchable like the 8372A.

@mariosMSX
See above. You can't simply change the ROM, as the existing Agnus is not switchable. You must replace it with the 8372A Agnus, which is configurable to either PAL or NTSC via pin 41.
Jumper JP4 connects to that pin: you will need to unlink JP4 so the 8372A Agnus will default to PAL timings upon power up (obviously JP4 is irrelevant if an 8370/8371 Agnus is installed).

Since you already have the correct oscillator, that's all it takes to have a PAL A500. And that's how you determine the PAL-ness or NTSC-ness of an A500: PAL/NTSC oscillator AND PAL/NTSC Agnus (or Agnus mode, in the case of 8372A), respectively.
 
i remember with minimegichip ntsc on my a500 in Italy, the sound on game pacmania run fast

run sysinfo and scout for more info
 
I change the Agnus with a 8372A and the A500 runs great.

I would like to thank everyone how wrote here and helped me
THANKS (y)
 
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