Review of the AMD Radeon RX 7900 XTX and XT: the XTX beats the Nvidia RTX 4080 for $200 less, except in power efficiency and ray tracing, and the XT comes close 電腦收購

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increasing cost and complexity of building gigantic, monolithic chips on cutting-edge manufacturing processes. Today, AMD is trying to solve the latter two problems with the launch of its Radeon RX 7900 series GPUs.
Further ReadingNvidia GeForce RTX 4080 review: Second only to the 4090—for now
At $899 and $999, the RX 7900 XT and RX 7900 XTX are still objectively expensive—but because they’re not a further escalation over the starting price of the RX 6900 XT, both cards are what pass for a bargain in today’s GPU market. If you’re looking for cards that can consistently handle 4K gaming at 60 fps and higher, these GPUs do it for less than Nvidia’s latest, and they’re good enough and fast enough that they’ll hopefully start driving Nvidia’s prices down a bit, too.
But Nvidia still retains some key advantages that complicate an easy David-and-Goliath narrative. These GPUs don’t quite feel like a Ryzen moment for AMD’s graphics division—a turning point where a scrappy AMD manages to make a big dent in the market share of an entrenched, complacent competitor. But if you can actually find them for their starting prices, they’re the first sign we’ve had in a while that some relief is coming for high-end-but-price-conscious PC gamers.
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Bigger Navi
Enlarge / AMD’s chiplet design is visible in this shot—a large center die with most of the compute resources, and six smaller dies containing cache and the memory controllers.AMD
The RX 7000 series is the third version of the RDNA GPU architecture, also occasionally referred to as “Navi,” after the codenames of the GPU chips themselves. RDNA 3 doesn’t add anything that feels as significant as RDNA 2’s ray-tracing support, but AMD has added plenty of extra hardware and made important under-the-hood changes.
The most significant is a new chiplet-based approach, similar in concept to the one AMD uses for its Ryzen CPUs. Rather than building the entire GPU die on one manufacturing process—increasing the die’s size and therefore the chances that some or all of it could be defective—AMD is building the main Navi 3 GPU die on a 5 nm TSMC manufacturing process and a series of smaller memory controller dies (MCDs) on a 6 nm process. These chips are all linked together with a high-speed interconnect, which AMD says can transfer data at speeds of up to 5.3 terabytes per second.
Further ReadingEverything you need to know about Zen 4, socket AM5, and AMD’s newest chipsets
The main graphics compute die (GCD) contains most of the hardware you think of when you think of a GPU—compute units, shaders, ray-tracing hardware, the media encoding and decoding block, and display output. Both the 7900 XTX and XT use the same Navi 31 GCD, but the XTX runs at higher clocks and has more CUs and stream processors enabled. The XTX has 96 CUs and 6,144 stream processors, while the XT has 84 CUs and 5,376 stream processors. Both cards represent a jump up from the Navi 21 die used in the RX 6900 series, which maxed out at 80 CUs and 5,120 stream processors (and that’s before you account for other performance-boosting improvements).
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Enlarge / RDNA 3 brings a little more of everything to AMD’s top-tier GPUs, from CU counts to memory bandwidth. AMD
The MCDs all include a single 64-bit memory controller and 16MB of AMD’s Infinity Cache, and they demonstrate the advantages of a chiplet-based approach. The 7900 XTX has a 384-bit-wide memory bus and 96MB of Infinity Cache, where the 7900 XT has a 320-bit bus and 80MB of cache; to accomplish this, all AMD has to do is remove an MCD. The exact same MCDs can be reused up and down the stack with all of the different RDNA 3 GCDs that AMD chooses to release, from low-end products with a single MCD up to midrange GPUs that use between two and four. Defects in MCD dies won’t require the larger, more complex GCDs to be thrown out or binned, and vice-versa.
In the realm of all-new features for RDNA 3, there are three things of note. First, the GPUs include new AI accelerators, which could be useful both for the plethora of AI-assisted content creation that has sprung up in the last year and for AI-assisted upscaling (if AMD chooses to implement it in some future version of its FSR upscaling algorithm; both DLSS and XeSS use AI for upscaling, but FSR 2.0 doesn’t).
Second, the video encoding and decoding block supports hardware-accelerated encoding for the AV1 video codec, just like the RTX 4000 series and Intel’s Arc GPUs. This should be useful for both content creators and streamers who want to stream higher-resolution video or video at the same resolution while using less bandwidth.
And third, the “Radiance Display Engine” adds DisplayPort 2.1 support to the GPUs. Monitors that take full advantage of DisplayPort 2.1’s extra bandwidth don’t really exist as of this writing, but when

（圖／翻攝自蘋果官網）
蘋果宣布自行打造 ARM 架構的 Mac 處理器，並攜手台積電，接連推出 M1、M1 Pro 和 M1 Max 三款讓人印象深刻的自研晶片，整體表現亦有超越老牌處理器大廠 Intel 的情形。

不過，據跑分平台 Geekbench 數據，Intel 的第 12 代「Core i9-12900HK」處理器，似乎有重新逆轉蘋果的跡象。以 電腦收購msi 的 GE76 Raider 電腦，以及蘋果的新款 14 吋 MacBook Pro 進行測試，i9-12900HK 在單核繳出 1,838 分，多核 12,707 分，皆領先 M1 Max 的水準，超出的幅度約在 3.5 ~ 4% 之間。

但測試的外媒《Macworld》也發現，雖然 i9-12900HK 效能確實更強，不過蘋果的 ARM 架構晶片仍在能耗上發揮優勢，在測試過程中僅有 40W 不到的能耗，而 i9-12900HK 機型則經常在 100W 上下，甚至一度達到 140W，差距來到兩倍以上。

請繼續往下閱讀…

此外，以 電腦收購msi 的 GE76 Raider 電腦測試，除了風扇全程狂轉，其大約 6 小時的影片播放續航，也與 MacBook Pro 的 17 小時有不少差異。

整體來說，《Macworld》認為雖然 Intel 第 12 代的 Alder Lake 架構仍然讓人印象深刻，但表現是用更大的能耗換來，在用戶體驗上不一定更好。此外，蘋果也預計會在今年，推出 M2 晶片，有望帶來更強的 GPU 效能和能耗管理，可能讓 Intel 面臨新一輪的挑戰。

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