Re: 1551 Repair - 28 pin 6523 Wanted

From: Rob Eaglestone <>
Date: Sun, 9 Mar 2014 15:42:40 -0500
Message-ID: <>
I'm just a spectator here, but it seems like this sort of accumulated
mass-knowledge should be put into a Wiki.  I mean, I want to build
Commodore hardware someday, and this sort of advice and data seems very
useful to me.

On Sunday, March 9, 2014, smf <> wrote:

> Well, TED does it and it works.
> The 6566 was designed while they were waiting for fast enough drams to
> use, the 6567 was then hacked so they could get the c64 out of the door.
> There is no real way of determining why they did what they did & it's so
> long ago their recollection is likely to be incorrect.
> With TED they had the benefit of hindsight and were able to work with dram
> manufacturers during the design process. It also wasn't designed for speed
> (no sprite dma needed and an additional bad line for colour fetches from
> dram etc).
> FWIW the Amiga 1000 ended up using the same scheme as the C64, so agnus
> only controlled it's own access to chip ram. The fat agnus designed for the
> a500 had the motherboard multiplexers integrated so it controls all access.
> The A3000 was the same with a bit of extra magic on the motherboard to
> allow the agnus to alternate between two banks of ram so the cpu could have
> 32 bit access to it without a new agnus. For AGA they pushed the magic deep
> into Alice, so dma could fetch 32 bits but the blitter/copper etc were
> still 16 bit.
>       Message was sent through the cbm-hackers mailing list

       Message was sent through the cbm-hackers mailing list
Received on 2014-03-09 21:02:11

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