exxos's Atari, Amiga & retro forum

Cyprian wrote: 09 Feb 2024 12:57

terriblefire wrote: 08 Feb 2024 17:03 On top of that the ECS chipset is really slow.

I wonder how to understand that, because if I remember correctly, according to Toni Wilen (WinUAE developer) AGA and ECS chipsets are run at the same clock speed - 3.5MHz, the CPU needs two bus cycles to access Chip RAM and it has 16bit access to AGA/ECS hardware registers.

ECS is half the speed of AGA because the data bus is 16bit. There is nothing more complicated than that. It means writes to video memory are half the speed. AGA machines a CPU can write to chip at 7mb. Its 3.5 on a ECS machine.

On top of that AGA machines can pull out data from chip ram at x2 the speed as it can be done with half as many memory accesses. This leaves more DMA slots available.

Cyprian wrote: 09 Feb 2024 12:57
I wonder how to understand that, because if I remember correctly, according to Toni Wilen (WinUAE developer) AGA and ECS chipsets are run at the same clock speed - 3.5MHz, the CPU needs two bus cycles to access Chip RAM and it has 16bit access to AGA/ECS hardware registers.

From the AGA functional specification...

How about a Zorro II? I have a Amiga 1200 with Zorro busboard, I do have a Zorro II for a Amiga 500 and hopefully soon for a CDTV.I haven't tested Amiga 500 Zorro with RTG, but would it be same speed than Amiga 1200?

Thanks.

utri007 wrote: 10 Feb 2024 11:50 How about a Zorro II? I have a Amiga 1200 with Zorro busboard, I do have a Zorro II for a Amiga 500 and hopefully soon for a CDTV.I haven't tested Amiga 500 Zorro with RTG, but would it be same speed than Amiga 1200?

Thanks.

I defo think ZII is worth having everywhere as it allows peripherals to be used.

terriblefire wrote: 10 Feb 2024 09:09

Cyprian wrote: 09 Feb 2024 12:57
I wonder how to understand that, because if I remember correctly, according to Toni Wilen (WinUAE developer) AGA and ECS chipsets are run at the same clock speed - 3.5MHz, the CPU needs two bus cycles to access Chip RAM and it has 16bit access to AGA/ECS hardware registers.

From the AGA functional specification...

Screenshot 2024-02-10 at 09.08.36.png

yes, I know the Chipram bus has been extended from 16-bit in OCS/ECS to 32-bit in AGA, but I thought something else had been improved (e.g. better access time to chipram).
Anyway I've just found out that Amiga 1200 still has 16 bit chips, e.g. DMA chip 'Alice' :
https://en.wikipedia.org/wiki/MOS_Technology_Agnus

Cyprian wrote: 10 Feb 2024 13:07 yes, I know the Chipram bus has been extended from 16-bit in OCS/ECS to 32-bit in AGA, but I thought something else had been improved (e.g. better access time to chipram).
Anyway I've just found out that Amiga 1200 still has 16 bit chips, e.g. DMA chip 'Alice' :
https://en.wikipedia.org/wiki/MOS_Technology_Agnus

The 7Mb/s write figure is the main one. Its easily measurable.