Re: Guru Meditation Exact Visual Specs

From: Gerrit Heitsch <>
Date: Fri, 12 Aug 2016 17:56:16 +0200
Message-ID: <>
On 08/12/2016 12:57 PM, wrote:
>> On 2016-08-12, at 08:07, Gerrit Heitsch <> wrote:
>>> PAL and NTSC machines use different Agnus chips:
>>> 252125-01    IC 8361 AGNUS NTSC    AMIGA-1000
>>> 252362-01    IC 8367 AGNUS PAL    AMIGA-1000
>>> 318069-02    IC 8372 FATAGNUS    AMIGA-2000
>>> 318069-03    IC 8375 HIRES AGNUS    2M A-3000
>>> 318069-10    IC 8375 R2 AGNUS HR    PAL SMT A-500+/A-600
>>> 318069-11    IC 8375 R2 AGNUS HR    NTSC SMT
>>> 318069-16    IC 8375 R01M HR AGNUS    PAL 65NS AMIGA-2000
>>> 318069-17    IC 8375 R01M HR AGNUS    NTSC 65NS AMIGA-2000
>>> 318069-18    IC SM CSG 8375R0 SUP    AGNUS
>>> 318070-01    IC 8370 R3 FAT AGNUS    NTSC AMIGA-500
>>> 318071-01    IC 8371 R1 FAT AGNUS    PAL AMIGA-500
>>> 390544-01    IC 8375 FAT AGNUS    AMIGA-500+
>>> 390544-02    IC 8375 AGNUS 2 MEG    NTSC A500+
>> That list is not quite correct...
>> The A3000 came with 8372AB or 8372B while the A2000 and A500 used the 8372A until they switched over to the 8375.
> As my rusty memory serves - there were 8371s in the earlier both A500s and A2000s. The 8375 was used in A500+ / A600 (the latter AFAIR) but not in the A2000.

Yes, the ones that used 256Kx1 DRAMs since the 8370/71 supplied only an 
8Bit Refresh. The 8372 had more Bits in the Refresh counter so they 
could finally use 256Kx4 DRAMs. Those were the Rev 6.x boards in the 
A2000 and I think Rev 7 and up in the A500.

You could, of course, use a 8372 with 256Kx1 DRAMs without problems. 
Using a 8371 with 256Kx4 usually works as long as the display DMA is 
running (and supplying refresh that way), but in the right combination 
you might run into problems.

>> It was never explained why there was a 8375, the 8372 was already ECS and could address 2 MB in the version used in the A3000.
> True - I /think/ there might have been pinout changes for 8375 but can't be sure now. Would need to check the old docs. I vaguely recall that unlike 8371 => 8372, 8375s were not a drop-in replacements for the earlier ones.

What they did with some 8375 was to expose Vbb to the outside via a pin 
and then connect a 100nF capacitor between this pin and GND. There are 
some 8375 that will replace a 8372A, but you HAVE to open the 
NTSC/PAL-Jumper, not doing this will ground Vbb. Adding the capacitor is 
a good idea as well.

Maybe the yields on the 8372 were too low and the 8375 fixed that? There 
are no new features in the 8375 as far as I know.


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Received on 2016-08-12 16:00:03

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