I am definitely interested in buying one!

Just take my money Serge.

bnz99 wrote on 2021-05-15, 11:51:

I'm curious though: it seems to be designed for use without a fan or heatsink. Won't that possibly cause thermal issues with the cm4?

The Pi 4 SoC (and by extension the CM4) is known to run hot when at maximum clock speeds and CPU load; a heatsink is a good idea for any Raspberry Pi and they are very cheap (search AliExpress for "14mm x 14mm heatsink").

The Pi 4 will start to throttle itself when it reaches ~80C, and even at that temperature, it is still very far away from harm. Raspberry Pis are designed to be safely run without any additional cooling whatsoever and can take a lot of punishment.

mt32-pi doesn't come close to maxing-out the Pi 4 - one core and the GPU are completely unused. In my testing, with the default clock speed of 1.5GHz, the Pi 4 will reach about ~70C sitting on a desk with a simple aluminium heatsink attached.

However, if the config.txt is edited to underclock the Pi 4 down to 600Mhz, the temperature drops all the way down to ~53C, which is much more comfortable and will be kinder to surrounding components like your sound card. Below 600MHz, audio distortion can start to appear as the CPU won't be able to render fast enough at those reduced speeds.

The next release of mt32-pi will - in addition to support for the CM4 (and therefore the McCake) - include an updated config.txt with reduced clock speeds for the Pi 4 out of the box to save energy and reduce temperature. The user can increase them again if they want to raise quality/polyphony settings beyond the defaults.

Also, the airflow of a PC case with fans will help a lot especially if you have a small heatsink on the Pi, so I'd expect a few degrees less if it's installed in a case with good airflow.

TL;DR - don't worry about it too much.

Would this board be compatible with CHILL II?

Thanks for the comprehensive answer dopefish. The undercloking solution sounds great.

mihai wrote on 2021-05-16, 06:10:

Would this board be compatible with CHILL II?

Yes, there are solder bridges at the bottom to select between floppy power and header power
if powered through header, it works fine on CHiLL II, which can provide the needed current

Looks great! I'm really interested in getting one.

This looks thicker than normal waveblaster boards. Does it fit between two ISA cards or is it necessary to leave one slot unused?

well this is not a "normal" waveblaster board 😁
but there is just enough space to fit 2 ISA cards one next to the other:

it is very crammed but they will fit... probably some airflow will be needed in this case

but it will work way better if the next neighbor ISA card is not full height - a slim PCI NIC or ISA I/O will be perfect

Just checked last video from Serge. Looks like it is now a single board connected to the GPIO of an rpi right ? Model 4 mandatory or any older will do the job ? Still got some to recycle 😁

McCake goes on a wavetable header.

the PI Hat board should work on RPI 3, 3A+ and 4.

This is awesome work!

mihai wrote on 2021-05-17, 17:19:

McCake goes on a wavetable header.

the PI Hat board should work on RPI 3, 3A+ and 4.

Damn ! I'm gonna have to buy both of them then... 😁

This project amuses me to no end, it's fantastic. 😁

But since we're already putting an SoC into the host machine that would equate to a SciFi supercomputer in the 90s, why don't we go one step further and connect the Raspi directly to the ISA bus, either with an adapter board for GPIO or via USB? 😁
Then we could do the whole soundcard (or any card, really) in software on the Raspi and we'd have a truly general purpose ISA card that can get better with the software on the connected Raspberry Pi.
I'm sure there's reasons why that wouldn't just work like that, but it's fun to imagine anyway.

BraveToaster wrote on 2021-05-17, 20:27:

This project amuses me to no end, it's fantastic. :D […]
Show full quote

This project amuses me to no end, it's fantastic. 😁

But since we're already putting an SoC into the host machine that would equate to a SciFi supercomputer in the 90s, why don't we go one step further and connect the Raspi directly to the ISA bus, either with an adapter board for GPIO or via USB? 😁
Then we could do the whole soundcard (or any card, really) in software on the Raspi and we'd have a truly general purpose ISA card that can get better with the software on the connected Raspberry Pi.
I'm sure there's reasons why that wouldn't just work like that, but it's fun to imagine anyway.

There are PCI sound cards that have wave table headers, so this would work on more systems. You'd also have to worry if whatever software emulation you are using is 100% accurate versus a real sound card.

This requires no new drivers, just install it on a sound card you are already using and go.

SScorpio wrote on 2021-05-17, 22:39:

There are PCI sound cards that have wave table headers, so this would work on more systems. You'd also have to worry if whatever software emulation you are using is 100% accurate versus a real sound card.
This requires no new drivers, just install it on a sound card you are already using and go.

Sure, I understand that, and as I said: this project is great as it is.

I'm just imagining this one step further: instead of hooking up the Raspberry Pi to a wavetable header of an ISA soundcard and make it the MIDI synthesizer, why not go further and hook up the Raspberry directly to the ISA bus? We already have really good emulation of all the sound cards (SB16, GUS, CMS, etc.) from the DOSBox project - it would be a ton of fun to hook that up to real hardware straight on the ISA bus. Instead of uploading different sound fonts, you could switch the card from SB16 mode to GUS mode for example - and of course it could still behave like an MPU401 with an MT32 connected as well. 😀
In the end it's just a matter which interface you use to bring the old hardware together with the new one. I'm just wondering aloud whether that interface could be the ISA bus.

BraveToaster wrote on 2021-05-18, 13:41:

Sure, I understand that, and as I said: this project is great as it is.

I'm just imagining this one step further: instead of hooking up the Raspberry Pi to a wavetable header of an ISA soundcard and make it the MIDI synthesizer, why not go further and hook up the Raspberry directly to the ISA bus? We already have really good emulation of all the sound cards (SB16, GUS, CMS, etc.) from the DOSBox project - it would be a ton of fun to hook that up to real hardware straight on the ISA bus. Instead of uploading different sound fonts, you could switch the card from SB16 mode to GUS mode for example - and of course it could still behave like an MPU401 with an MT32 connected as well. 😀
In the end it's just a matter which interface you use to bring the old hardware together with the new one. I'm just wondering aloud whether that interface could be the ISA bus.

You want the BitchinFastAudio 3000, no idea if Alan is still developing it.

https://www.youtube.com/watch?v=0aCy3ccLZzo

Naaah, way too complicated and hence expensive. It started nice but then he started to add more and more features… I’d rather have just a sound card without all the frills.

inching closer to doing a production run.
next batch of 4 working perfectly fine,
thanks to PJ for soldering assistance.

Nice! Can you provide a step-file of the whole board? I'm planning to make a standalone case for it.