RE: 8520/21

From: Martin Hoffmann-Vetter <>
Date: Thu, 5 Mar 2015 21:31:30 +0100
Message-ID: <007f01d05783$5d744e60$>
> Remember, Commodore made a lot of different chips just because they
> could...

...and need it.

> Why a special CPU for the 264 series and the C128 instead of
> just using a different bond out of the 6510? The 8500 is the 6510 in

At this time, CSG build many chips in HMOS. So if Commodore need a huge package of CPUs, they build a new version in HMOS. This isn't a special CPU, it's a variant of an existing CPU in HMOS.

So i think, it's cheapter to design a new HMOS version and build it later in many parts. So this calculation is only true if the number of produced chips are high enougth!

> Or why the 6523 and later the 6525 (6523 with IRQs)? And
> then all the 77xx-TTL replacements... Or the 6529...

They need these chips. First they can buy it from an other manufactor. In any case, these chips are not available, so they build it self. What's the alternative for a 6529? It's a simple chip, so they designed it, build it und use it. And for Commodore with the CSG it's no problem.

And back to the 8520/8521: they need a CIA with a linear counter. It's planned to produced many Amigas. You can use a existing production or create a new one. You have a chance to producted the new chips cheapter as the old one. They changed from NMOS to HMOS. Why not changing the TOD registers?

After that all, Commodore developed the C64C with HMOS too. Now they need a CIA in HMOS with the old TOD design. So they create the new chip 8521. This was a problem from Commodore, all designs are only for the actually situation. No one looks into the future.


       Message was sent through the cbm-hackers mailing list
Received on 2015-03-05 21:00:05

Archive generated by hypermail 2.2.0.