BRbrucehoult·Jul 26, 2023
I've also found the 1.5 GHz in-order VF2 does remarkably well vs the 1.85 GHz OoO LPi4A on software build tasks, though not as extreme as Richard shows.
I'm lazy and using the original Image-55 on my 8 GB VF2, and the Debian that came preloaded in the eMMC on the LPi4A. My mass-production LPi4A arrived yesterday, I haven't tried it yet, tests are on the beta board that arrived a couple of months ago.
On pure CPU core + L1 cache tests (e.g. https://hoult.org/primes.txt) the LPi4A is considerably faster.
The LPi4A is also much faster on memcpy tests.
https://hoult.org/TH1520_memcpy.txt
https://hoult.org/JH7110_memcpy.txt
My build test is an RVV 0.7.1-enabled snapshot of the gnu toolchain (gcc 9.2) that I use on the TH1520 and SG2042 (and various chips with C906 cores with RVV 0.7.1). Newlib, non-multilib (just rv64gcv) build. I used the sam
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e Samsung 2 TB external USB3 SSD drive for src/build trees on both boards. https://github.com/brucehoult/riscv-gnu-toolchain
VF2:
real 107m52.116s
user 348m49.800s
sys 16m27.529s
LPi4A:
real 122m16.099s
user 400m17.737s
sys 23m8.567s
Neither board is thermal throttling at all. I have the supplied fan sitting loosely on top of the LPi4A CPU (I also try tests without the fan ... it throttles a lot, taking 166m on this test). The VF2 is without a fan -- doesn't need it.
The LPi4A has more L1 cache, but only 1 MB of L2 vs 2 MB on the VF2. But the LPi4A's RAM is twice as fast as the VF2's L2 cache! At least for streaming -- I haven't tried random.
It's a mystery.