News New SiFive RISC-V cores

[soresu]

SiFive just introduced new RISC-V CPU cores, named the U84 and the U87.

The U84 has 3.1x more performance at 7nm than the previous 16nm U74 core, this is a combination of 2.3x IPC and 1.4x clock frequency (I realise the math seems off, but it's their press release).

The U84 core area is about 0.28mm2 (7nm), with a quad core (with 2MB L2$) taking up a whopping 2.63mm2.

They claim competitive performance with the Cortex A72, though exact numbers are not forthcoming, only a footnote implying they were comparing against a Cortex A72 implemented at 16nm.

The U87 is similar to the above core (I presume for lack of further information and similarity of core number), but with vector processing too, further details on U87 will supposedly follow in a later press release.

(Sorry for the anaemic round of posts guys, I get a little over enthusiastic with a low attention span every so often.....)

Link here.

 

[soresu]

Anandtech just posted a full article on the release.

It's somewhat easier to read than the SiFive PR announcement:

"SiFive’s design goals for the U8-Series are quite straightforward: Compared to an Arm Cortex-A72, the U8-Series aims to be comparable in performance, while offering 1.5x better power efficiency at the same time as using half the area."

Sounds not dissimilar to the ProMIPS core announcement comparing to the Cortex A15 way back when.

Link here.

If indeed it is 1.5x better efficiency, I imagine that this is not counting NEON code performance too, considering how much of a speedup over C that brings.

 

[Thala]

I would not give much about the efficiency claims - as they did not disclose how this was measured and in which environment.

 

[soresu]

I would not give much about the efficiency claims - as they did not disclose how this was measured and in which environment.

Especially given the immature state of R5 software support, they are probably in a worse position now than ARM was when they started getting serious about server hopes.