MiniMig with AGA

[Darrin]

I think I have enough information to write a new one from scratch. Only time is the limit.

Looks like my joke about "Picasso 2010" wasn't too far off the mark!  Picasso 2011?  

[freqmax]

Darrin, When did you write that joke?

[Darrin]

Darrin, When did you write that joke?

LOL.  and we still have 42 days to go...  

[ChaosLord]

@Yaqube

                               
 The Replay is equipped with 24-bit Audio DAC (capable of 192 kHz sampling rate) but right now only 16-bit precision is used. It may change when the CPU core is fast enough to mix channels in the Hi-Fi mode with reasonable rate but I'm rather sceptical if it's of any use as the noise floor of the board isn't as low.

Am I to understand that this is just 1 DAC, capable of a single audio channel of output?

Wouldn't there need to be 2 DACs for stereo output?

If it is DMA driven then why does the CPU need to do mixing?

                               
 The standard Amiga audio output is mixed with the 16-bit AHI output.

This is hardware mixed in FPGA code, correct?

[freqmax]

Chaoslord, I think he simple used DAC in the general sense, not in "a DAC" sense. And DMA only transfers, doesn't process. But the FPGA could be configured to do something in "hardware".

[yaqube]

Am I to understand that this is just 1 DAC, capable of a single audio channel of output?

That was a little bit misleading, actually it's one stereo DAC IC containing two separate DACs, each for left and right channel.

If it is DMA driven then why does the CPU need to do mixing?

Because it supports only one (stereo) channel. To off load the CPU we need more hardware channels. It's really frustrating to see the CPU fully loaded mixing four audio channels with decent rate when the same job can be done by Paula with almost no CPU load. Definitely we need more hardware channels.

This is hardware mixed in FPGA code, correct?

Yep, the four Paula native audio channels and two 16-bit ones are down-mixed in hardware.

[ChaosLord]

That was a little bit misleading, actually it's one stereo DAC IC containing two separate DACs, each for left and right channel.


Because it supports only one (stereo) channel.

What format does the DAC IC take?  1 word left + 1 word right, repeat.  ?

That is the DAC IC reads 1 DMA stream of data to produce 1 stereo ouput?

While Paula reads 2 distinct DMA streams of data to produce 1 stereo output.

[yaqube]

What format does the DAC IC take?  1 word left + 1 word right, repeat.  ?

Exactly, the words the DAC is fed can contain up to 24 meaningful bits. For further details please have a look at the DAC's datasheet.

That is the DAC IC reads 1 DMA stream of data to produce 1 stereo ouput?

Not exactly, the DAC is fed with the data stream from the I2S controller (located in the FPGA). This stream contains down-mixed data from Paula's  audio channels and from the AHI stereo channel (the AHI sound is provided by the extra DMA controller).

While Paula reads 2 distinct DMA streams of data to produce 1 stereo output.

Actually Paula reads 4 mono channels and down-mix them to form two channels for stereo output (two mono channels go to the left and two to the right). This stereo output is further down-mixed with stereo output from AHI sound module and is sent to the DAC IC.

[Everblue]

Is it possible to pre-order one of these yet? Or its still a way off?

[bloodline]

Only schematics available.

Page 2, are the ARM's ADC inputs just tied to the ground? Why not use them for audio sampling?

[mikej]

The ARM ADC inputs are connected. Four to the rear "cable" connector and four to the main board stacking expansion connector.

I imagined the rear connector being used for joystick/buttons/analog joypad etc but you could use them for line level audio.

The expansion board could contain a decent mic input if there was demand.
I want to keep the feature set on the main board to a basic level to keep the main board cost down.I imagine a number of expansion boards for different applications could appear.

The schematics and top/bottom component placement are available.
Detailed mechanical drawings will also be available.

I'm not taking any pre-orders just yet - until we have got these boards tested and Yaqube has had a play.
Best,
Mike

[Darrin]

Mike,

Could you give us a quick summary of what cores should be available to run on this board when it is tested and ready for bulk production and what others are under development?

[Everblue]

I guess at this point its wise to hold off purchase a minimig and wait for this!

By the way, can PAL games be forced to output @ 75hz or 100hz to add compatability with more monitors while retaining smooth scrolling?

[freqmax]

If the memory transfer capacity is up to it. And vertical scan is a multiple of 25 Hz. Ie let minimig write to a display area #0 ,let the monitor read #1. Then swap when vertical sync:s occour at the same time.

Don't forget that the same memory transfer capacity is needed for feeding instructions to the cpu, samples to paula, floppy transfers, harddisc dma etc.. as well.

[mikej]

For composite/VHS outputs you get real NTSC/PAL exactly like the original machine which will drive 15K linescan monitors. In the same way,the RGB analog out of the DVI can be connected to RGB monitors or SCART connectors.

You can cable the DVI output to HDMI (50/60Hz Progressive or Interlaced) and modern TVs will be fine with this.

For "computer" monitors the best way is for the cores to support higher resolution (1280x720) resolution for example. I'm looking at various frame buffer options, but they will add a frame of latency. This may be fine. T

/Mike

[trip6]

Great... When doing this please keep in mind game compatability and testing with various side scrolling and overhead scrolling games.

For composite/VHS outputs you get real NTSC/PAL exactly like the original machine which will drive 15K linescan monitors. In the same way,the RGB analog out of the DVI can be connected to RGB monitors or SCART connectors.

You can cable the DVI output to HDMI (50/60Hz Progressive or Interlaced) and modern TVs will be fine with this.

For "computer" monitors the best way is for the cores to support higher resolution (1280x720) resolution for example. I'm looking at various frame buffer options, but they will add a frame of latency. This may be fine. T

/Mike