AMD EPYC 7643 vs AMD EPYC 7773X Comparison

The AMD EPYC 7773X and AMD EPYC 7643 are both 7 nm Zen 3 server processors on the AMD Socket SP3 platform, but benchmark results show a consistent and decisive performance gap. The 7773X wins all six head-to-head comparisons, with every single-core and multi-core test showing a 20.1% advantage. The 7643 is the lower-power, lower-core-count option, while the 7773X leverages a massive L3 cache to deliver uniformly higher scores.

The Verdict

The data is unambiguous: the AMD EPYC 7773X outperforms the AMD EPYC 7643 in every recorded benchmark. In Cinebench R15, R20, and R23, the 7773X leads by exactly 20.1% in both single-core and multi-core tests. The 7773X scores 7,825 in Cinebench R15 multi-core versus 6,515 for the 7643; 32,608 versus 27,149 in R20 multi-core; and 77,639 versus 64,642 in R23 multi-core. The single-core results follow the same pattern: 1,104 versus 919 in R15, 4,603 versus 3,832 in R20, and 10,960 versus 9,126 in R23. Every delta is identical at 20.1%, suggesting a consistent architectural advantage rather than workload-specific scaling.

The 7643 is not a weak processor—it holds an average benchmark score of 18,697 and sits in the 73rd percentile of all CPUs, identical to the 7773X. However, the 7773X’s average score of 18,979 is higher, and its nearest rivals include the Intel Core i5-1335U at 18,982 (0% delta) and the Intel Core i5-12400F at 19,039 (-0.3% delta). The 7643’s nearest rival is the Intel Core i5-12400 at 18,683 (0.1% delta). These rival comparisons place both EPYC parts in similar company, but the head-to-head data shows the 7773X is strictly superior to the 7643 in every measured category.

For buyers choosing strictly on performance, the 7773X is the clear pick. The 7643 makes sense only when the 64-core part’s higher TDP of 280 watts versus 225 watts is a constraint, or when the 48-core count of the 7643 is sufficient and the 20.1% performance delta is not required. The 7773X’s launch MSRP is $8800; the 7643’s is $4995. Neither processor has an unlocked multiplier, so no manual overclocking is available to close the gap.

Architecture Differences

Both processors are built on TSMC’s 7 nm process with 33,200 million transistors and an 8x 81 mm² die configuration. They share the same Zen 3 architecture, the AMD Socket SP3 socket, DDR4 memory support with an eight-channel memory bus, and 204.8 GB/s of memory bandwidth. Both support ECC memory and provide Gen 4 PCIe with 128 lanes from the CPU. The core counts diverge: the 7773X has 64 cores and 128 threads, while the 7643 has 48 cores and 96 threads. Base and boost clocks also differ slightly, with the 7643 running at 2.30 GHz base and 3.60 GHz boost, versus 2.20 GHz base and 3.50 GHz boost for the 7773X.

The defining difference is L3 cache. The 7773X carries 768 MB of shared L3 cache, triple the 256 MB found on the 7643. Both have identical L1 and L2 caches at 64 KB per core and 512 KB per core, respectively. The 7773X is codenamed Milan-X, while the 7643 is plain Milan. The 7773X launched on 2022-03-21, roughly a year after the 7643’s 2021-03-14 release. The 7773X’s production status is Active, as is the 7643’s.

The 20.1% performance delta across all tests is notable because the 7773X has a lower base clock and lower boost clock than the 7643. This indicates the L3 cache advantage of 768 MB versus 256 MB is the primary driver of the performance difference, not raw clock speed. The additional 16 cores and 32 threads on the 7773X also contribute to multi-core wins, but the single-core wins at a lower clock speed point squarely at the cache hierarchy as the deciding factor. The 7773X’s TDP is 280 watts, 55 watts higher than the 7643’s 225 watts, reflecting the cost of the larger cache and additional cores.

Head-to-Head Benchmarks

The head-to-head results are remarkably uniform. In Cinebench R15 multi-core, the 7773X scores 7,825 against the 7643’s 6,515, a 20.1% advantage. The R15 single-core test shows 1,104 versus 919, again 20.1% ahead. Moving to Cinebench R20, the 7773X posts 32,608 multi-core and 4,603 single-core, while the 7643 manages 27,149 and 3,832, respectively. The R23 results continue the trend: 77,639 multi-core versus 64,642, and 10,960 single-core versus 9,126. Every single delta is exactly 20.1%.

This consistency is the most telling detail. If the 7773X’s advantage were purely core-count-driven, the multi-core deltas would likely be larger than the single-core deltas. Instead, both scale identically. The 7643’s higher boost clock of 3.60 GHz versus 3.50 GHz does not help it in single-core tests; the 7773X still wins by the same margin. The 7773X also has a Geekbench multi-core score of 15,554 and a single-core score of 1,536, which the 7643 lacks entirely in the fact pack.

The 7643’s best showing is in Cinebench R23 multi-core, where it reaches 64,642—still 12,997 points behind the 7773X. The 7773X’s worst relative performance is in Geekbench single-core, but there is no 7643 comparison for that test. The 7643’s average benchmark score is 18,697, which is only 1.5% lower than the 7773X’s 18,979, but that average is dragged down by the absence of Geekbench data and the fact that the 7643 has fewer benchmark entries. In direct comparisons, the 7773X wins all six tests with no exceptions.

FAQ

Q: Which processor has more cores?

A: The AMD EPYC 7773X has 64 cores and 128 threads, while the AMD EPYC 7643 has 48 cores and 96 threads.

Q: What is the L3 cache difference?

A: The 7773X has 768 MB of shared L3 cache, while the 7643 has 256 MB of shared L3 cache. Both use 64 KB L1 and 512 KB L2 per core.

Q: Are the single-core performance gaps the same as multi-core?

A: Yes. In every Cinebench test (R15, R20, R23), the 7773X leads by exactly 20.1% in both single-core and multi-core scores.

Q: Which processor has a higher boost clock?

A: The 7643 has a higher boost clock at 3.60 GHz versus the 7773X’s 3.50 GHz, yet the 7773X still wins all single-core benchmarks.

Q: Do both processors support the same memory configuration?

A: Yes, both support DDR4 with an eight-channel memory bus and 204.8 GB/s of memory bandwidth, and both support ECC memory.

Q: What is the TDP of each processor?

A: The 7773X has a TDP of 280 watts, while the 7643 has a TDP of 225 watts.

Where Each One Wins

The AMD EPYC 7773X wins every benchmark category recorded. It is the correct choice for workloads that demand maximum throughput, given its 64 cores and 128 threads against the 7643’s 48 cores and 96 threads. Its 768 MB L3 cache provides a decisive edge in single-core tests despite a lower boost clock, making it suitable for latency-sensitive applications where cache hits matter more than raw frequency. The 7773X’s Cinebench R23 multi-core score of 77,639 versus 64,642 for the 7643 indicates it can handle heavily threaded rendering or simulation workloads with 20.1% more output. Its Geekbench multi-core score of 15,554 further validates its position as the higher-performing part.

The AMD EPYC 7643 wins only in the sense of lower power draw and lower launch MSRP. At 225 watts TDP versus 280 watts, it consumes less power under load. Its launch MSRP is $4995, compared to $8800 for the 7773X. For deployments where the 48-core count is sufficient and the 20.1% performance delta is not critical, the 7643 offers a lower thermal envelope. It also has a slightly higher boost clock at 3.60 GHz, though benchmark data shows this does not translate into a performance win. The 7643’s average benchmark score of 18,697 places it in the same 73rd percentile as the 7773X, indicating that in the broader CPU landscape, both are comparable, but the 7773X is strictly ahead in direct head-to-head tests.

In summary, the 7773X is the performance leader across all measured benchmarks, with its cache size being the likely differentiator. The 7643 is the more conservative choice for power-constrained environments, but it cannot match the 7773X’s output in any test. The data shows no scenario where the 7643 outperforms the 7773X.