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benjojo posted 19 May 2025 16:20 +0000

TIL there are PCIe Sound cards (such as the one pictured, a ASUS XONAR_AE) that are actually two devices glued together, a PCIe USB card, and a USB Sound card.

I cannot tell if this is incredibly stupid (this is obviously sub-optimal), or incredibly smart (this will not have any driver issues)

A PCIe sound card

benjojo replied 19 May 2025 17:03 +0000
in reply to: https://mstdn.ca/users/jsph/statuses/114535532273949485

@jsph yeah, I mean the reason I am in this situation is because my desktop is a EYPC, and those do not have sound cards, or even a chipset (everything is wired into the CPU directly).

This is the same with "Threadripper" boards, who seem to have sound, but via just a USB Sound chip on the motherboard to keep up appearances that it isnt all just a giant IO expander for the CPU

erincandescent@akko... replied 19 May 2025 22:40 +0000
in reply to: https://benjojo.co.uk/u/benjojo/h/652h8lh972D4Vyz4f3

@benjojo @jsph Threadrippers aren’t SoCs; all Threadripper boards have a chipset. I don’t see why its strictly required though; everything required to boot hangs directly off of the CPU (SPI to BIOS ROM + eSPI to legacy IO/BMC/TPM/etc), but this seems to be the way AMD have designed it and the way the motherboards are built.

Most mystifying of all, the sTRX5 (latest gen ThreadRipper Pro) motherboard I’m looking at for reference has a Realtek ALC1220 hanging directly off of the CPU. AMD built HD Audio support into the ThreadRipper IO die. This realy, really smells like they built it with the intention of supporting ThreadRipper machines withut a chipset.

manawyrm@chaos.socia.. replied 19 May 2025 20:38 +0000
in reply to: https://benjojo.co.uk/u/benjojo/h/943lrvXRwYL9S33KV1

@benjojo You'll also need to be very careful with the hardware design with such a thing -> USBs physical layer isn't quite symmetrical, frames are separated by pulling both D- and D+ to the same potential. Because USB frames are sent at 1 (or 8 for USB HS) kHz, you'll get a weird high-pitched noise if you have any leakage/interference from the USB lines at all.

I'm sure most people reading this have heard it before but probably didn't know why: https://0xstubs.org/understanding-usb-microphone-whine/

HeNeArXn@chaos.socia.. replied 19 May 2025 16:51 +0000
in reply to: https://benjojo.co.uk/u/benjojo/h/943lrvXRwYL9S33KV1

@benjojo The biggest recommendation when people have issues with USB audio interfaces is (although usually more at the professional/recording side of things) "ensure you use the right USB host controller (i.e. not one shared with high traffic devices, avoid known incompatibilities with specific chipsets)". This covers all these aspects, is efficient to develop, and is more than sufficient for the use case here, so I'm not sure it is suboptimal in any way that matters.