Surprising.
Just benched, between last JCE and last xmrstak, official release, not recompiled myself.
Using autoconfig to mine Monero v8 in both cases, 4 threads on my Core2Quad Xeon oc@ 2.666G
[2018-12-25 20:23:41] : Your CPU doesn't support hardware AES. Don't expect high hashrates.
[2018-12-25 20:23:41] : Mining coin: cryptonight_v8
[2018-12-25 20:23:41] : Starting 2x thread, affinity: 0.
[2018-12-25 20:23:41] : hwloc: memory pinned
[2018-12-25 20:23:41] : Starting 1x thread, affinity: 1.
[2018-12-25 20:23:41] : hwloc: memory pinned
[2018-12-25 20:23:41] : Starting 2x thread, affinity: 2.
[2018-12-25 20:23:41] : hwloc: memory pinned
[2018-12-25 20:23:41] : Starting 1x thread, affinity: 3.
[2018-12-25 20:23:41] : hwloc: memory pinned
[2018-12-25 20:25:15] : New block detected.
HASHRATE REPORT - CPU
| ID | 10s | 60s | 15m | ID | 10s | 60s | 15m |
| 0 | 12.5 | 11.5 | (na) | 1 | 14.2 | 13.5 | (na) |
| 2 | 13.6 | 13.0 | (na) | 3 | 14.8 | 14.4 | (na) |
Totals (CPU): 55.2 52.4 0.0 H/s
For Windows 64-bits
Analyzing Processors topology...
Intel(R) Xeon(R) CPU L5408 @ 2.13GHz
Assembly codename: core2_sse4
Preparing 4 Mining Threads...
20:26:36 | Hashrate CPU Thread 0: 22.92 h/s
20:26:36 | Hashrate CPU Thread 1: 23.79 h/s
20:26:36 | Hashrate CPU Thread 2: 24.33 h/s
20:26:36 | Hashrate CPU Thread 3: 24.52 h/s
20:26:36 | Total: 95.55 h/s - Max: 96.24 h/s
So that's even more than +30%.
What CPU and algo did you test on?