Oracle charges 1.0 for any POWER9 core. Which means that SMT8 cores (which are twice as big as SMT4 cores) get you more performance with less licensing costs.

So what would you rather buy? A 24-core SMT4 Nimbus chip, or an 12-core SMT8 Cumulus chip?

The two chips have the same number of execution units. They both support 96 threads. But the 12-core SMT8 Cumulus chip will have half the license costs from Oracle.

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For DB2...

The SMT8 model (E950) only has a 100x multiplier for DB2, while SMT4 models have a 70x multiplier. So you're only paying 30% more per core (E950), despite getting twice the execution resources.

Even the top end SMT8 model (E980) has a 120x multiplier. So you're still saving big bucks on licensing.

The point is that a POWER core costs twice as much as an Intel/AMD core so SMT8 doesn't save as much money as you might think.

What would you rather buy? A 24-core x86 or a 12-core SMT8 POWER?

The 12-core POWER10 will have 120MB of L3 cache and 1000GBps main-memory bandwidth with 96-threads.

That's unified L3 cache by the way, none of the "16MB/CCX with remote off-chip L3 caches being slower than DDR4 reads" that EPYC has.

Intel Xeon Platinum 8180 only has 38.5MB L3 across 28 cores / 56-threads. With 6-memory controllers at 2666 MHz (21GBps per stick), that's 126 GBps bandwidth.

AMD EPYC really only has 16MB L3 per CCX (because the other L3 cache is "remote" and slower than DDR4). With 8 memory controllers at 2666 MHz, we're at 170 GBps bandwidth on 64-threads.

If we're talking about "best CPU for in-memory database", its pretty clear that POWER9 / POWER10 is the winner. You get the fewest cores (license-cost hack) with the highest L3 and RAM bandwidths, with the most threads supported.

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On the other hand, x86 has far superior single-threaded performance, far superior SIMD units, and is generally cheaper. For compute-heavy situations (raytracing, H265 encoding, etc. etc.) the x86 is superior.

But as far as being a thin processor supporting as much memory bandwidth as possible (with the lowest per-core licensing costs), POWER9 / POWER10 clearly wins.

And again: those SMT8 cores are no slouch. They can handle 4-threads with very little slowdown, and the full 8-threads only has a modest slowdown. They're designed to execute many threads, instead of speeding up a single thread (which happens to be really good for databases anyway, where your CPU will spend large amounts of time waiting on RAM to respond instead of computing).