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Old 17 March 2011, 14:24   #53
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AndyLandy's Avatar
Join Date: Dec 2009
Location: Southampton / UK
Posts: 91
Originally Posted by CDTV1991 View Post
Yes I have, but it seems that I wasn't looking hard enough!

I now see that the CDTV has ECS chipset and 1MB Chip RAM.

Do some Amiga games require more Chip/Fast RAM? It never seemed to be a concern back in the day when I had an A500+ and then an A1200.
Strictly speaking:

There are two chips involved in the difference between OCS and ECS. Denise and Agnus:
Denise is easy: There are two types, the OCS Denise (MOS 8362) and the ECS 'Super' Denise (MOS 8373). The ECS Denise provides the additional display screenmodes associated with the ECS chipset.

Agnus is a little more complicated: There are many different revisions (See the Wikipedia article for more information.) For the purposes of this discussion, there are three 'classes' of Agnus. The original Agnus and Fat Agnus (MOS 8371) can only address 512k of ChipRAM, these are most definitely OCS. The A500+, A600 and A3000 have 2MB ChipRAM Agnus chips (8375, 8372B), these are most definitely ECS.

The only room for debate is the 8372A Agnus, which can address up to 1MB of ChipRAM. You find these:
  • In r6 A500s, configured with only 512k chip
  • In r6 A2000s, configured for the full 1MB chip
  • In the CDTV, again with 1MB chip
(As an aside, Kickstart is often included with OCS/ECS differences, since 2.0 was released at the same time as the ECS.)

Invariably, machines with 8372A Agnuses shipped with OCS Denise and Kickstart 1.3, so it's hard to justify it as 'ECS', but it's certainly a step up from the earlier 512k chips. I tend to refer to it as the 'half-ECS Agnus'

This is the case with the CDTV, it shipped with Kick 1.3 and OCS Denise. Of course, if you swap the Denise for a Super Denise, plug in a Megachip and give it Kickstart 2.0 or higher, to all intents and purposes it becomes a full ECS machine.

Of course, just to cause confusion, there are many examples of people getting mixed chipsets when they bought A500s or A2000s near the ECS debut.
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