[sdiy] Understanding 80s Synth Architectures

[rburnett at richieburnett.co.uk]

Wow, that is pretty impressive.  And a substantial undertaking to figure 
out how it all works and then comment it!  How long did that take you!?

Do you think the original code was written in assembly, or compiled from 
a higher level language like C?

-Richie,

On 2022-02-05 04:10, Anthony via Synth-diy wrote:
> In case you're interested in understanding how the firmware of these
> 80s synthesisers was implemented, I've done an annotated disassembly
> of the Yamaha DX7's firmware ROM. This repository contains a lot of
> information regarding how the synth itself functioned, and was
> designed. Hopefully it provides a little bit of insight into how
> synths in this era were designed! That's the reason I began this
> project. I was interested in understanding the exact same topic.
> 
> https://github.com/ajxs/yamaha_dx7_rom_disassembly
> 
>  ------- Original Message -------
> On Friday, February 4th, 2022 at 9:22 PM, ackolonges fds via Synth-diy
> <synth-diy at synth-diy.org> wrote:
> 
>> Hi Everyone,
>> 
>> As the local SDIYer I sometimes get asked to try and fix synths
>> from the 80s like various Rolands, Korgs, Oberheims etc. and I
>> generally just try to pinpoint the rough area of the issue and
>> replace logic chips until the issue is resolved...
>> 
>> Most of these synths have a CPU connected to everything via a
>> parallel address bus and a parallel data bus, with all sorts of glue
>> logic chips doing various things. They also usually just have 1 DAC,
>> time-domain multiplexed to all of the different parameters via more
>> logic chips.
>> 
>> Obviously this is very different to the modern ways that
>> microcontrollers and DACs are used in synths, and since I wasn't
>> around in the 80s, these older architectures are very foreign to me.
>> To aid in my troubleshooting efforts, I would love to better
>> understand the details of how these architectures work, so I was
>> wondering if anyone on here would be able to point me to any
>> resources that could explain these types of systems to me, be they
>> websites, articles, or books?
>> 
>> Thanks a lot for any advice you might have.
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