It may be the answer to the current version of the Thunderbolt graphics dock - MEmu CX hands-on testing

1. Composition and selection of external graphics cards

There are too many graphics card docking stations: NVme to PCIe, Thunderbolt 3, 4 and USB4, NVme to OCUlink + COUlink to PCIe. There are various protocols and principles, and there are many companies that are launching products. The author previously purchased MEmu B, and later directly chose MEmu BX for path dependence. In terms of price alone, MEmu is definitely cheap in Thunderbolt graphics docks, and the circuit design level is in place. On the whole, in addition to not enough bells and whistles, it is definitely the most cost-effective choice. This time, as soon as I watched the CX come out, I thought that the size of lying down is smaller, and it supports DC power supply, which means that the size of the whole set of configurations can be reduced, so I hurriedly started.

Needless to say, the thin and light book is not much to say: either Intel's notebooks that support the Thunderbolt interface, these basically have EVO certification; Either AMD's 7840H/U, 8845HS notebooks that support USB4 interfaces; Silicon M-series processors can use the graphics dock to connect to the PCIe interface, but they do not support the graphics card. It's simpler on the side of the small host, considering the price, it is more suitable for the Ryzen small host with USB4 interface. This test platform is Xuanpai Xingyao, in addition to USB4 interface, there is another OCULink interface. The author's version is 7840HS, taking advantage of the national subsidy in September last year, and finally less than 3,001 to start. Now you can basically take a notebook with 8845HS at this price, and it is indeed early to buy early and enjoy early, and there is a discount for late purchase.

2. Equipment layout and commissioning

Windows 11 already has a Thunderbolt driver integrated, so you don't have to worry about installing the driver yourself. In Windows 10, there is no integrated driver, so you have to install it manually. The latest version of the Thunderbolt driver is 1.41.1340.0 before it is written, please download it from the "link" link. In the past, there was no need to refer to the various complicated installation processes, and now you only need to download and install it.

Let's review the peripheral interface of MEmu CX: This side of the single interface is a DC 7.4*5.0 power supply interface, which is a large round port of Dell many years ago, but now there are many 240-400W DC-ATX and gallium nitride power supplies to choose from. The other two power supply inputs are a USB-C interface and DC 5.5*2.5 that support PD100W, PD interface is suitable for non-graphics card expansion play, after all, the low-power independent display that can be used for transcoding is basically inferior to the performance of the nuclear display, and DC 5.5*2.5 has a large number of 230W and below large bricks to choose from, seriously, how can there be a 230W power supply if you have a game book at home, with a serious single 8Pin network card is not stressful at all. Other SD、TF card slot,2.5G wired network port,USB-A 3.0(10Gbps) interface,DP1.4a interface,mini-DP interface needless to say,This time the two Thunderbolt 4 interfaces both support100W reverse charging,This can be a perfect line for the core display thin and light notebook。

The MEmu supports reverse power supply, and if you use an external graphics dock for your laptop, you only need to connect a Thunderbolt 4 full-featured cable. The author is using a 230W large brick power supply, and the RX5700 is the default TDP 150W, so I still connect the power supply to the notebook separately, if you have a 330W power supply or a configuration like this, just one line on the line. The cable provided by MEmu is the CPU 8Pin female port, and the cable that comes with it is the CPU 8Pin male port to the PCIe 8Pin male port, so the author customized the PCIe 8Pin female port to dual male port short cable this time, which is just enough for this RX5700 supply. For higher power graphics cards, consider using the ATX power supply directly.

The sequence of turning on and off the graphics card dock and the notebook is actually one principle: disconnect the electric wire, and cut off the power of the moving wire. When the power is off, connect the cable to avoid static electricity breaking down the lightning interface, and you need to turn off the power and pull the cable first, and try not to perform hot-swap operations. Of course, if you are sure that there is no static electricity, you can also connect the graphics card dock to the laptop after all the power is connected, after all, the Thunderbolt itself is designed to support hot swapping.

3. Comparison of use effect and performance

The author still wants to emphasize again,The external graphics card is only a temporary solution,Compared with direct installation, there will naturally be various shortcomings。 But there must be a trade-off in everything, and you can't always have both and everything. The author's satisfaction with CX is still very high after the overall use, compared to B and BX, it is indeed a lot less, and the improvement in portability is too comfortable for the author's business trip.

Now the external graphics card is an RX5700, and the mining card I bought directly back then was quite stable, but it was slightly deformed. I still haven't opened the dust yet, and I'm afraid that the heat dissipation and screws will affect the motherboard of the graphics card. The power cable is a PCIe 8pin female to dual male short cable, which can be connected with the power supply cable that comes with the CX.

More users are also more concerned about the performance loss of the graphics dock, how much performance can a graphics card play? What is the best graphics card for me? After all, everyone adheres to the idea of "I don't need it but you have to", and the performance of the graphics card is limited by the actual bandwidth, especially the bandwidth left for the graphics card in the inner screen mode will be compressed. Taking Xuanpai Xingyao and ZeroMoment SEi 14 as an example, they can be seen that the gap between the internal and external screens is not large, and the bus bandwidth performance of different platforms is very large. Then the follow-up will be tested with Xuanpai Xingyao to see how big the gap between the internal and external screens is.

As can be seen from the test results of Time Spy and Fire Strike of 3D Mark 11, the performance loss in the inner screen state is not serious. The gap in benchmarks is around 10-20%, with only the Fire Strike achieving a performance gap of nearly 40%.

The first game chose Black Myth: Wukong, set to 2K resolution, high by default, and an oversample rate of 50. Based on the 95% frame rate, the performance gap between the internal and external screens is roughly about 20%, and the average frame rate is also about 20%. The lowest frame rate is a common drop spike, and the frame rate performance is stable after removing the spikes.

To the Shadow of the Tomb Raider benchmark, set the resolution to 2K and set it to the highest. It can be seen that the gap between the inner and outer screens is also around 30%. Of course, this is the most extreme case. If the preset is lowered appropriately, the gap between the inner and outer screens will be narrowed as the bandwidth demand of the PCIe bus decreases.

Video information backhaul will occupy bandwidth, and the performance of the natural external screen will be stronger than that of the internal screen. For users who mainly play games, it must be the idea of using the external screen as much as possible. In particular, people's perception of the lowest frame is obvious, and the PCIe bandwidth of Thunderbolt 3/4 is in a range that has the greatest impact on the lowest frame, which really affects the use experience of using the elongated frame generation time. Production applications generally do not have high bandwidth requirements, and the same is true for local verification of scientific research instances, so the difference between internal and external screens has little impact. But thanks to the fact that MEmu CX uses JHL7540, it has better bandwidth dynamic allocation capabilities, so there is not much difference in the actual inner screen performance, and the actual game experience is no problem at all.

The number of interfaces and bandwidth comparable to that of the Thunderbolt docking station is also one of the reasons why the author intends to use this MEmu CX as the main equipment in the next stage. After all, the author basically has a desk on a business trip, and the interface of the notebook alone is really not enough, and in the past, I had to bring an additional docking station in many cases. In the future, I should change to a single-fan or shorter dual-fan graphics card, and then get a high-power gallium nitride power supply. After all, the size of the integrated external graphics card from a serious computer manufacturer is not much smaller.

4 Summary

As an expansion device, the final size of the graphics dock actually depends on the specific graphics card and power supply. When it comes to traveling on a business trip, the length is good, but the main thing is that the thickness will be limited, and the size of the cabin suitcase is there, and the docking station that is about to catch up with the overall size of the compact MATX case should be used at home. Xiaoyaowu CX has improved another section in portability, after all, it is not thick when it is upside down, it is necessary to remember to install the PCIe baffle, and fix it in advance when you use it.

And CX comes with reverse power supply, notebooks with Thunderbolt/USB4 are directly connected to one line, as long as it is not connected to a high-power gaming laptop, this 100W reverse power supply power is completely sufficient. And the most important thing is that the full-blooded JHL7540 competitors have to start at 3,000, even a thunderbolt that can only expand the interface has to be hundreds of dollars larger, and the bare metal with this performance and interface specifications is only ¥999 at this price, what more do you want a bicycle. Of course, the power supply needs to be purchased separately, if your needs are similar to the author, it is recommended to either choose a DC 5.5 * 2.5 large brick power supply, which is cheap enough and large in quantity, or try the DC 7.4 * 5.0 of high-power gallium nitride, and the power can be directly full.

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