Still confused 8375 Agnus

[AmigaPixel]

hi all
I am revisiting an earlier post by amigan24. I am still confused as hell. The Big Book of Amiga Hardware list all of the 8375 versions as 2mb. I have one I tested a few years ago and it was 1mb. It's some where in the house I'll try to find it for the numbers on it. BBoAh also list the Mega Chip but does not state whether or not it is DKB's Mega Chip. Is the same one? Also I was wondering which if any need to be modified like the DKB MegaChip and which do not? Thanks

Here is how it list the versions of the 8375:


Agnus (2MB)     8372AB     318069-03     A3000 (PAL), A3000T (PAL) (came after 8375B)
Agnus (2MB)    8372AB    318069-039    A3000 (NTSC)
Agnus (2MB)    8372B    318069-03    MegAChip (NTSC)
Agnus (2MB)    8375 R0    318069-18    A500+ (PAL), A600 (PAL)
Agnus (2MB)    8375    318069-10    A600 (PAL)
Agnus (2MB)    8375 R2    318069-10    A500+ (PAL), A600 (PAL)
Agnus (2MB)    8375    318069-11    A600 (NTSC), MegAChip (NTSC), Mini Megi Chip (NTSC)
Agnus (2MB)    8375 R2    318069-11    Mini Mega Chip (NTSC)
Agnus (2MB)    8375    318069-17    A500 (NTSC), A2000 (NTSC)
Agnus (2MB)    8375    318069-19    A3000 (NTSC), A3000T (NTSC)
Agnus (2MB)    8375    390544-01    A500+ (PAL), A600 (PAL)
Agnus (2MB)    8375    390544-02    A500+ (NTSC), A600 (NTSC)

[AmigaPixel]

I found this related posting from 2006, by Alex Holland basically asking the same thing but he points out errors in the table. Could anybody clear this up?

http://newsgroups.derkeiler.com/Archive/Comp/comp.sys.amiga.hardware/2006-02/msg00025.html

[AmigaPixel]

Correction it was barney who posted the orginal question.

[Zac67]

BBoAH isn't accurate on Agnus details. There is at least one 1 MB 8375 version - I got a batch directly from C= when I ordered ECS replacements for A500/2000.

[alexh]

hi all
I am revisiting an earlier post by amigan24. I am still confused as hell. The Big Book of Amiga Hardware list all of the 8375 versions as 2mb.

No it doesnt! The list does contain the 1MB parts. It is inaccurate, misleading and has entries missing but it does contain 1MB 8375 parts.

http://www.bboah.com/index.php?action=artikel&cat=51&id=2174&artlang=en&highlight=agnus

BBoAh also list the Mega Chip but does not state whether or not it is DKB's Mega Chip. Is the same one?

It does state who makes it and yes it is DKB.

http://www.bboah.com/index.php?action=artikel&cat=69&id=3061&artlang=en&highlight=megachip

Also I was wondering which if any need to be modified like the DKB MegaChip and which do not?

?? In English please

P.S. Take a look here at the original thread I started when I asked for help.

http://www.amiga.org/forums/showthread.php?t=20895

[Zac67]

That was a highly informative thread, wish the details would make it into BBoAH - have you tried emailing the maintainer?

To my mind the four digits code is so misleading that we should use the long codes only.

[arnljot]

Agree completely, also remember that there are several mirrors of bboah out there which are not maintained or updated anymore.

Personally I prefere the old layout, so I don´t mind that they are a bit inaccurate :-P

[AmigaPixel]

@alexh Thanks for the link to the thread.

[AmigaPixel]

I going to open up my A2000 to see what the 8372A has for the rest of the numbers. My 8375 Agnus is at a different location, I hope I can get to it soon so I can check it out.

[AmigaPixel]

On the 2mb 8375 Agnus chips that are compatible for the A500/A2000, do they need any modification like the DKB Mega Chip does?

[AmigaPixel]

Ok, to make sure, which of the NTSC 8375 2mb Agnus chips are compatible with the A2000 and what are the full set of numbers?

thanks

[Zac67]

2 MB Agnuses are NOT compatible with any A2000 (nor A500) without adaptation. The adapter defines which kind of Agnus you need, the A3000 or the A500+/A600 one.

[AmigaPixel]

@Zac67

 Thanks that helps to clear it up more, however I didn't think the A3000 needs an adapter? it already has 2mb chip ram right, unless some early models came with 1mb only.  I guess it means I will have to find a DKB MegaChip, or is there another brand?Thanks

[AmigaPixel]

@Zac67
 
Ok I found the answer to the my question on wether there were other chip adapters. They probably were not as common as the DKB brand I would imagine but I might be wrong. I do seem to recall seeing the DCE Mini mega chip advertised enough.

I do see now from BBOAH that some A3000 did come only with 1mb but ready to upgrade to 2mb chip. I should look these things up before I ask questions, even if they turn out to be partially wrong  sometimes.

[AmigaPixel]

Alright,
I think this all falling into place. Correct me if I am wrong (and you know you will!) The Fat Agnus is the DMA controller as well as other functions. It does not hold the actual chip ram but can address 512k, 1mb or 2mb depending on the chip revision.  Hence the need for an adapter on A2000 and A500, the adapter which has the 2mb chip ram on it along with the Agnus 8375 or the socket and the wiring to the Gary chip.

In regards to the A3000, the ones that came with only 1mb chip but had the expansion socket for 2mb, I assume then the Agnus had to be upgraded as well. if so did they require an adapter too or could the chips be plugged right in?

I love learning this stuff, even if it is 20 years later!