Paula output rate

[snyp]

Hi guys,

if anyone knows a lot about amiga hardware, i would really appreciate clarification on this point;

i am making software that includes emulation of the amiga's paula chip.

the cpu clock of the amiga was easy to switch between pal and ntsc.

however, most commonly i've read that paula's output is 3579545 Hz, which is a serial baud rate for NTSC timing.

other places i have read that paula's output is dependent on the system clock, either 3579545 Hz NTSC clock or 3546895 Hz PAL clock.

given that a user could switch the cpu clock very easily, when this was done, was the switch also syncronised in the paula chip?

the amiga was most widely used in europe, utilising the PAL cpu and video clock speeds, 50fps..

NTSC is 60fps..

in popular tracker formats, using the video vblank for timing, switching between PAL and NTSC obviously shows a significant increase in the number of sequencing 'steps' called per second; thus an increase in the speed of the music by 20%.

also, if the paula did in fact have a switchable clock speed, the pitch of the audio would show a significant change, due to the change in output rate.

is all this true of a real amiga?

currently i have emulated PAL video clock with NTSC paula rate.. do i need to rewrite my engine?

[Eliotg]

Originally Posted by snyp

Hi guys,

if anyone knows a lot about amiga hardware, i would really appreciate clarification on this point;

i am making software that includes emulation of the amiga's paula chip.

the cpu clock of the amiga was easy to switch between pal and ntsc.

however, most commonly i've read that paula's output is 3579545 Hz, which is a serial baud rate for NTSC timing.

other places i have read that paula's output is dependent on the system clock, either 3579545 Hz NTSC clock or 3546895 Hz PAL clock.

given that a user could switch the cpu clock very easily, when this was done, was the switch also syncronised in the paula chip?

the amiga was most widely used in europe, utilising the PAL cpu and video clock speeds, 50fps..

NTSC is 60fps..

in popular tracker formats, using the video vblank for timing, switching between PAL and NTSC obviously shows a significant increase in the number of sequencing 'steps' called per second; thus an increase in the speed of the music by 20%.

also, if the paula did in fact have a switchable clock speed, the pitch of the audio would show a significant change, due to the change in output rate.

is all this true of a real amiga?

currently i have emulated PAL video clock with NTSC paula rate.. do i need to rewrite my engine?

paula maximum output in ntsc or a pal screen is 28 khz
correct me someone if Im wrong

[Toni Wilen]

Paula's only clock source is master clock (divided by 4 I think) so Paula's audio rate has to change between PAL and NTSC. (same chip, different clock)

paula maximum output in ntsc or a pal screen is 28 khz

This has nothing to do with OPs question

[snyp]

hi tony,

thanks for the reply

i will rewrite my code

[TheDarkCoder]

I confirm, PAL Amiga sound different form NTSC ones!

[Thorham]

Originally Posted by Eliotg

paula maximum output in ntsc or a pal screen is 28 khz
correct me someone if Im wrong

28 khz is related to the audio dma rate, which is linked to the screen mode bandwith:

15 khz screen mode=28 khz audio dma
30 khz screen mode=56 khz audio dma

Paula's audio output rate and audio dma are separate, and Paula can go much faster than the audio dma