Re: Additional SIDs

From: Richard Atkinson <>
Date: Thu, 1 Dec 2011 17:24:18 -0000
Message-ID: <68462AD81FEA4EB8B528A3D2CD495914@abion>
Strikes me $D7xx is the best place for an internal SID modification, being 
as that is spare in the C128 and actually decoded. No idea who decided $D420 
was a good idea, that takes way more in the way of address decoding. 
Obviously easier in this day of programmable logic devices, but what about a 
good old 74LS139 for decoding $D400 further?

External hardware expansions are likely to use $DExx and $DFxx, including 
SID cartridges. What I'd really, really, really like to see attached to a 
C64 is an Ensoniq 5503 DOC. Rainer, you probably know more about this chip 
than anyone else on this list. It's designed for 6809 bus accesses isn't it? 
Might be possible to add to a C64 in $DFxx or wherever with minimal extra 

Imagine having a 24 bit phase accumulator and 16 bit frequency registers, 
but instead of sending 12 bits to a DAC, having an 8 bit memory access for 
every step and outputting the result on a DAC. Then multiplex that phase 
accumulator up to 32 times for up to 32 channel sound. That's basically what 
the Ensoniq DOC is. It really is the spiritual successor of SID.


From: "Rainer Buchty" <>
Sent: Thursday, December 01, 2011 2:51 PM
To: <>
Subject: Re: Additional SIDs

> On Wed, 30 Nov 2011, Groepaz wrote:
>> actually most "older software" uses DE00 or DF00, ie whats available at 
>> the cartridge port. D700 i havent seen in the wild, i think =)
> Although DE00 is a particularly bad choice for SIDs, as MIDI interfaces 
> like to reside here (DE04-DE07).
> Rainer
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Received on 2011-12-01 18:00:25

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