Both the CPU and GPU Valve chose for the Steam Machine are cut down ("binned") versions of silicon AMD likely had lying around. The CPU is a laptop part which didn't sell in huge volume and has had the GPU fused off. The GPU has several CUs disabled compared to top-of-the-line. This indicates to me that Valve is using silicon which AMD either couldn't use otherwise, or couldn't sell for top price.
You can see the alternative with PS5 and Xbox, where AMD designed and produced large bespoke custom chips. Versions of these chips which don't fully pass QA could have a few defective cores or CUs fused off and used elsewhere, but we don't see that outside of some very niche Chinese motherboards.
Valve's approach instead allows them to re-use standard PC components which just didn't quite meet muster.
So in effect, "our next console will be a bunch of refurbished PCs we have sourced from local junkyard" is exactly what Valve did here.
You can see the alternative with PS5 and Xbox, where AMD designed and produced large bespoke custom chips. Versions of these chips which don't fully pass QA could have a few defective cores or CUs fused off and used elsewhere, but we don't see that outside of some very niche Chinese motherboards.
Valve's approach instead allows them to re-use standard PC components which just didn't quite meet muster.
So in effect, "our next console will be a bunch of refurbished PCs we have sourced from local junkyard" is exactly what Valve did here.