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Old 13 November 2017, 22:24   #61
duga
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A1200 would of suffered immensely with only 1MB CR. 2MB was only just about enough and not being able to go any further was a mistake.
Really? How much memory is used by gfx + sound in an average AGA 2 MB RAM game? The rest can/will be placed in fast mem if available.
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Old 14 November 2017, 05:20   #62
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The Amiga 1200 chipset wouldn't allow for more than 2MB CR without further modification anyways. Which leads me to believe that they had something extra lined up for the A4000.

Most of the AGA video games were written for the 3rd Gen chipset and 2MB CR limit. Programmers would have had issues with the 2MB limit if they wanted to offer, more sound and graphics features in titles.

This is another reason why, if triple A 4th Gen chipset had of happened on the CD32, then maybe more Chip Ram could of been added? Maybe theses would of been the specifications: Triple A Chipset, 4MB CR with 2MB FR and 030. <Now that back in the day would of been mega !!

Then again, just imagine the price tag on this machine, if it had of been launched?

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Old 14 November 2017, 19:52   #63
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The Amiga 1200 chipset wouldn't allow for more than 2MB CR without further modification anyways.
I'm not talking about any chipset changes, I'm talking about 1 MB chip + 1 MB fast instead of 2 MB chip.
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Old 15 November 2017, 01:02   #64
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Yes that would of made a difference. You still have to take into consideration that, if it did have 1MB CR and 1MB FR the A1200 would still have advantages and disadvantages.

All this stated both the Chip and Fast are on 32bit bandwidth which again helps. Still amazes me that all the 16Bit Amiga's were mostly 32bit CPU's. It was the ALU and the external data bus that dragged it down to 16Bit. Also RAM was 16Bit but had to be.

CD32 with its AGA Chipset gave it 16.8 million colours against the 4096 found on earlier Amiga systems. All contributes to more data requirement, this is one of several reason why more CR would of made a massive difference. Specially on the 4th Gen Chipset. Yes FR is good but you can expand to 256MB, where as CR will never exceed 2MB.

I remember reading somewhere that those emulating the Amiga can make possible an Amiga system with 4MB Chip Ram. < DamienD might be able to clarify this?
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Old 15 November 2017, 11:06   #65
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The number of possible colours doesn't really require much more RAM - it's still palette and planar based, so while you need 24 bits to store a colour instead of 12 as with OCS/ECS, a 32-colour image still only needs the same amount of memory to store the bitmap, and only 48 bytes more RAM to store the palette. More bitplanes will take a bit more memory, but not as much as the number of extra colours might suggest (a 320*256, 32-colour bitmap takes up 50KB, whereas a 256-colour bitmap takes up 80KB, despite containing 8 times more colours).

Having said that, more chip RAM has the benefit of being able to store more frames of animation without having to do lots of fast-chip transfers for example, as well as longer, more detailed sound effects or music. So it is nice to have, and I expect a lot of AGA games used it in that way. The advantages of having fast RAM available at the expense of chip RAM would probably have been cancelled out by the need for the CPU to constantly transfer data from fast to chip as needed.

Having chip and fast on a 32-bit bus wasn't entirely a new idea for AGA - the A3000 also had 32-bit access to chip RAM.

As for emulation, yes, WinUAE lets you use up to 8MB of chip RAM. The only real reason the physical chips can't do it in the 1200/4000/CD32 is because they lack the addressing capability, possibly to save costs (keeping pin and trace counts down). Internally the chips use 24-bit addressing.
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Old 15 November 2017, 12:22   #66
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I remember reading somewhere that those emulating the Amiga can make possible an Amiga system with 4MB Chip Ram. < DamienD might be able to clarify this?
...not sure why you're asking me? I'm no Amiga hardware expert.
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Old 15 November 2017, 23:33   #67
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...not sure why you're asking me? I'm no Amiga hardware expert.
Asking you because you emulate Amiga, so thought you might of successfully managed to emulate an Amiga with 4MB chip ram?

It is NOT possible in the hardware world unless you can alter the Amiga's chipset, which is very unlikely, even for the most experienced user.

Although Daedalus I appreciate what you are saying. So who knows, maybe it can be done?
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Old 16 November 2017, 01:06   #68
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Although Daedalus I appreciate what you are saying. So who knows, maybe it can be done?
I find this a little confusing... To emulate 4MB of chip RAM? It most certainly can be done - as I said, WinUAE lets you emulate up to 8MB, and has done for many years.
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