Zhaoxin's KX-7000

Summary

Zhaoxin is a Chinese x86 CPU designer. The KaiXian KX-7000 is Zhaoxin’s latest CPU, and features a new architecture dubbed “世纪大道”. 世纪大道 is a road in Shanghai called “Century Avenue”, following Zhaoxin’s practice of naming architectures after Shanghai landmarks. Zhaoxin is notable because it’s a joint venture between VIA Technologies and the Shanghai municipal government. It inherits VIA’s x86-64 license, and also enjoys powerful government backing. That’s a potent combination, because Zhaoxin’s cores are positioned to take advantage of the strong x86-64 software ecosystem.x86-64 compatibility is just one part of the picture, because performance matters too. Zhaoxin’s previous LuJiaZui, implemented in the KX-6640MA, was clearly inadequate for handling modern applications. LuJiaZui was a 2-wide core with sub-3 GHz clock speeds and barely more reordering capacity than Intel’s Pentium II from 1997. Century Avenue takes aim at that performance problem.Century Avenue is a 4-wide, AVX2 capable core with an out-of-order execution window on par with Intel CPUs from the early 2010s. Besides making the core wider and more latency-tolerant, Zhaoxin targets higher clock speeds. The KX-7000 runs at 3.2 GHz, significantly faster than the KX-6640MA’s 2.6 GHz. Zhaoxin’s site claims the KX-7000 can reach 3.5-3.7 GHz, but I never saw the chip clock above 3.2 GHz.The KX-7000 has eight Century Avenue cores, and uses a chiplet setup reminiscent of single-CCD AMD Ryzen desktop parts. All eight cores sit on a die and share 32 MB of L3 cache. A second IO die connects to DRAM and other IO. Zhaoxin did not specify what process node they’re using. Techpowerup and Wccftech suggests it uses an unspecified 16nm node.At the frontend, instructions are fetched from a 64 KB 16-way instruction cache. The instruction cache can deliver 16 bytes per cycle, and feeds a 4-wide decoder. Century Avenue uses a thoroughly conventional frontend setup, without a loop buffer or op cache. Instruction cache bandwid...