AMD Ryzen 9 7900X Review: Is It Still Value Champion?
AMD’s recent launch of X3D for Zen4 (Socket AM5) feels right, but we can’t overlook a $600 entry point for the second-fiddle 7900X3D version. Pricing that seems out of reach caused us to ask whether the non-bolstered 7900X still holds its former position as a value leader. So, we got one.
Like the Ryzen 9 7950X of previous review, the 7900X comes with nothing more than the CPU, a case sticker, and a miniature printed warranty sheet. All of that extra space in the packaging is taken up by nothing more than a block of foam.
A CPU package is really nothing more than a circuit board with pins or contacts and some integrated circuits (aka “Chips”), and AMD’s recent CPU packages have included a somewhat traditional CPU core die and a separate I/O die. A key difference between AMD’s upper and lower models is that the better parts have twice as many core dice: Since each complex core die (CCD) has up to eight cores, it’s only the 7900X (12 cores) and 7950X (16 cores) that require two dice. We’ve seen photos of single CCD models that had a empty gap where the second CCD would have gone, but as for the four missing cores of the 7900X…going down from sixteen to twelve requires disabling half of the cores on one die. While AMD is almost certainly disabling the defective cores of defective dies at least part of the time to accomplish this, there’s a good chance that the firm may also be handicapping otherwise perfect cores for the purpose of order fulfillment.
|AMD Ryzen 9 7950X||AMD Ryzen 9 7900X||AMD Ryzen 7 7700X||AMD Ryzen 5 7600X|
|Boost Clock||Up to 5.7GHz||Up to 5.6GHz||Up to 5.4GHz||Up to 5.3GHz|
The 7900X technically has a higher base clock and lower maximum boost frequency than the 7950X, but the reality is that most boards will push either of these to the firmware’s power limit. Here’s what that looks like under a medium and a high load on the 7900X:
Upgrades to our classic test platform include PowerColor’s Red Devil Radeon 6750 XT and Sabrent’s Rocket 4 Plus 2TB NVMe SSD. We’re still look for a modern graphics card to use as a baseline for the Red Devil’s review.
|CPU Cooler||Alphacool Eisblock XPX CPU, Eisbecher D5 150mm, NexXxoS UT60 X-Flow 240mm|
|Motherboard||ASRock X670E Taichi: Socket AM5, BIOS 1.09|
|Graphics Card||Powercolor Red Devil Radeon 6750 XT: 2324-2623MHz GPU, 12GB GDDR6|
|DRAM||G.Skill F5-6000J3038F16GX2-TZ5N 2x16GB (32GB) DDR5-6000 CL30-38-38-96 1.35V|
|Power||be quiet! Dark Power Pro 10 850W: ATX12V v2.3, EPS12V, 80 PLUS Platinum|
|Hard Drive||Sabrent Rocket 4 Plus 2TB PCIe 4.0 M.2 SSD|
|Sound||Integrated HD Audio|
|Graphics Driver||AMD Adrenalin Edition 2022.10.1|
The rules for overclocking AMD’s current run of CPUs are more about thermal limits than actual voltage: We pushed the 7900X to 5525 MHz at 1.325V to find the fastest stable speed at which it would run Cinebench R23, where adding more voltage caused the CPU to overheat. The same thing happened at 5275 MHz and 1.260V under Prime95 small FFTs. For comparison, the 7950X would reach its thermal limit at 5400 MHz and 1.30V for Cinebench, and 5075 MHz/1.18V for Prime 95.
Despite its DRAM overclocking advantage, the 7900X barely outpaces the 7950X in overclocked memory bandwidth. The single CCD CPUs appear to be further limited by having only the bandwidth of a single core linked to the IOD memory controller.
Since we didn’t receive the X3D versions of these processors, we decided the prudent path would be to retain the motherboard’s original firmware to assure fair benchmark results…rather than retest everything following updates. The 7900X outpaced the 7950X in Sandra Bandwidth despite our precautions.
Unlike the 7600X that fell flat in 3DMark Time Spy’s CPU score compared to its full-fledged single-CCD sibling, the 7900X barely trails the 7950X in this metric. Unfortunately, 3DMark’s CPU Profile bit a pretty big hunk out of the 7900X’s pride.
There’s really very little to mention regarding PCMark 10 results, with its Digital Content Creation showing an almost perfect graduation in performance scale between all four CPU models.
We tossed the 720p results of F1 2021 as being far too inconsistent for a CPU comparison, and the remaining results only show that the 7600X is a little weak at QHD resolution. How anticlimactic.
The 7900X bows a little more deeply than we’d like in 7-Zip, though its twelve active cores still score well ahead of the 7700X’s eight. Scaling appears consistent through Cinebench, Corona Bench and Handbrake.
Power, Heat & Efficiency
The biggest surprise will likely be that our 7900X drew more energy at load than the 7950X, even though the 7900X has ¼ of its cores disabled. We may have gotten a bad draw.
Of course, more power means more heat, and it’s not like our cooler can magically increase in response to that added stress. And in case you’re wondering, those are delta temperatures, so you can add whatever your room temperature is to figure out how hot these would have been in your location.
Even with its 25% fewer cores causing large losses in timed benchmarks, the 7900X still came out only around 7.5% worse than the 7950X in overall performance. The problem is that it did not compensate reduced performance with reduced power consumption, and because of that its efficiency looks terrible.
Putting aside the poor energy efficiency of our 7900X sample, its still economical enough to fall almost perfectly in line with the value presented by the other three Zen4 CPU models. Yet while that makes AMD appear to be proficient at pricing, it removes any reason to label a particular product as a stand-out value. The 7900X is merely filling its expected role.
|AMD Ryzen 9 7900X|
|For those who can’t afford the 7950X, the 7900X appears a well-priced substitute.|