Update:

> It seems they can't even get their chips above 1.2 GHz.

Now it's official: only up to 1.2 GHz for Mamba.

https://myapmold.apm.com/MyAMCC/jsp/public/productDetail/product_detail.jsp?productID=APM86190
https://myapmold.apm.com/MyAMCC/jsp/public/productDetail/product_detail.jsp?productID=APM86290
https://myapmold.apm.com/MyAMCC/retrieveDocument/SNP/APM86190_PB_20120216.pdf
https://myapmold.apm.com/MyAMCC/retrieveDocument/SNP/APM86290_PB_20120216.pdf