Re: 1551 Repair - 28 pin 6523 Wanted

From: smf <*smf_at_null.net*> Date: Mon, 10 Mar 2014 10:32:45 -0000 Message-ID: <8170FEA878264582A929F4C02713BCCE@smf> · smf_at_null.net

>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. 
I would love there to be the equivalent of http://www.folklore.org/ for commodore

http://www.amazon.co.uk/Commodore-Company-Edge-2nd-Edition/dp/0973864966

http://www.youtube.com/watch?v=Z5ENMeGSK0M
http://www.youtube.com/watch?v=Zl_d3gGhsk8
http://www.youtube.com/watch?v=SQ1IkpqIF1E
http://www.youtube.com/watch?v=2E0QAWNaX5o
http://www.youtube.com/watch?v=COKza8FBmF8

The introduction 8 bit maintenance is pretty cool too 
http://www.youtube.com/watch?v=DXRvCnmLj7A
http://www.youtube.com/watch?v=h4so6WKcnv0

From: Rob Eaglestone 
Sent: Sunday, March 9, 2014 8:42 PM
To: cbm-hackers@musoftware.de 
Subject: Re: 1551 Repair - 28 pin 6523 Wanted

On Sunday, March 9, 2014, smf <smf@null.net> 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.

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