Friday, April 24th 2020
AMD Ryzen 3 3300X Isn't Just a Speed-Bump of the 3100: CCX Gymnastics at Play
AMD has announced its Ryzen 3 "Matisse" quad-core desktop processors, with two SKUs in the pipe, the $99 Ryzen 3 3100 and the $120 Ryzen 3 3300X. Both are 4-core/8-thread parts spaced apart by clock-speeds, or so we thought. According to an alleged AMD presentation slide leaked to the web, the differentiation between the two runs deeper than that. Both chips are based on the "Matisse" multi-chip module, with a single 8-core "Zen 2" chiplet that has four disabled cores. How AMD goes about disabling these cores appears to be the secret sauce behind the "X" on the 3300X.
Inside each "Zen 2" chiplet, the 8 cores are spread between two 4-core CCX (compute complexes). On the 3100, AMD disabled two cores per CCX, and halved the 16 MB L3 cache per CCX. So it ends up with a 2+2 core CCX configuration, 8+8 MB of L3 cache adding up to 16 MB. The 3300X takes the more scenic route. An entire CCX is disabled, all four cores are part of the same CCX. This design lowers inter-core latency among the cores, and more importantly. gives each of the four cores access to 16 MB of shared L3 cache. And then there's the speed-bump. This goes a long way in explaining how the 3300X is shown within striking distance of the Core i7-7700K in leaked Cinebench scores, and could provide a formidable gaming processor in the lower end.
Source:
HardwareLuxx.de
Inside each "Zen 2" chiplet, the 8 cores are spread between two 4-core CCX (compute complexes). On the 3100, AMD disabled two cores per CCX, and halved the 16 MB L3 cache per CCX. So it ends up with a 2+2 core CCX configuration, 8+8 MB of L3 cache adding up to 16 MB. The 3300X takes the more scenic route. An entire CCX is disabled, all four cores are part of the same CCX. This design lowers inter-core latency among the cores, and more importantly. gives each of the four cores access to 16 MB of shared L3 cache. And then there's the speed-bump. This goes a long way in explaining how the 3300X is shown within striking distance of the Core i7-7700K in leaked Cinebench scores, and could provide a formidable gaming processor in the lower end.
19 Comments on AMD Ryzen 3 3300X Isn't Just a Speed-Bump of the 3100: CCX Gymnastics at Play
I suspect that AMD will keep 1 chiplet Zen 3 cpu to lower clock speed and boost frequency to make sure it do not harm too much the 2 chiplets SKU.
By example
- 3950x CPU got released later when they had enough 8 core chiplet that go high in frequency
- Latest Epyc CPU are made from chiplet that have low count of working core but working cache.
- Theses cpu are made to collect the chiplet that have more than 2+ core not working per chiplet.
AMD goal is to maximise profits while reducing as much loss. I doubt they will try to sell willingly a chiplets that could go in a EPYC/Ryzen 7 or 9 in theses CPUs. They are probably everything that they couldn't sell otherwise in their lineup and they are just empying the stock.
So they get cpu models that can compete with intels lowest tier 10000 series, re using broken Chiplets = more profit to amd and less waste to be thrown out. Good for the environment. This just shows how beneficial Chiplet design really is. You can get a to tier cpu like 3950X and also a cheap quad-core out of same design and re use more Chiplets than a all in one chip design like Intel properly can re use.
Clockspeed is useful, but we're genuinely at a point where a lot of stuff now uses 8 threads or more. The difference between SMT and another real core is starting to get too big for the 4C/8T chips to hang with the pack. 4C/4T stuff is starting to bottleneck even moderate GPUs now, and 2C/4T is dead to me for anything that isn't effectively a webtop/netbook.