Amiga 500 PAL 50/60 Hz JP4 observations

grj · 07 October 2023, 10:58

I came across something interesting, thought I'd post here for posterity.

I've got two rev 6A motherboards. One of them has 8372A Agnus and JP4 cut or drilled open at the factory (I've had this one since it was brand new). The other one originally had 8371 Agnus and JP4 in pristine condition. They were both running at 50 Hz in these configurations.

Then I went on to upgrade the Agnus on the latter board to 8372A, and it switched to 60 Hz.

The JP4 50/60 Hz switch is nothing new, per se, but I find it interesting that Commodore were cutting JP4 at the factory when they were installing 8372A's. And 8371 ignores the jumper.

derSammler · 07 October 2023, 11:21

That's because the pin is GND by default. The 8371 does not care, as that pin has no function - it was reserved for future use. On the 8372, that pin on GND switches the Agnus to NTSC (8371 is PAL-only). For PAL systems, it must be cut therefore to start the 8372 Agnus in PAL mode. That's just how it works.

07 October 2023, 10:58	#1
grj Registered User Join Date: Sep 2023 Location: Finland Posts: 13	Amiga 500 PAL 50/60 Hz JP4 observations I came across something interesting, thought I'd post here for posterity. I've got two rev 6A motherboards. One of them has 8372A Agnus and JP4 cut or drilled open at the factory (I've had this one since it was brand new). The other one originally had 8371 Agnus and JP4 in pristine condition. They were both running at 50 Hz in these configurations. Then I went on to upgrade the Agnus on the latter board to 8372A, and it switched to 60 Hz. The JP4 50/60 Hz switch is nothing new, per se, but I find it interesting that Commodore were cutting JP4 at the factory when they were installing 8372A's. And 8371 ignores the jumper. Attached Thumbnails

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07 October 2023, 11:21	#2
derSammler Senior Member Join Date: Jun 2001 Location: Germany Posts: 1,667	That's because the pin is GND by default. The 8371 does not care, as that pin has no function - it was reserved for future use. On the 8372, that pin on GND switches the Agnus to NTSC (8371 is PAL-only). For PAL systems, it must be cut therefore to start the 8372 Agnus in PAL mode. That's just how it works.

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