HP Pro Mini 400 G9 review: An ultra-compact office computer

HP has several variations of mini PCs and the Pro Mini 400 is their most compact yet. The latest edition is called the G9 and it’s sold in many different configurations, with 12th or 13th generation Intel Core i5 or Core i7 for desktop computers and various amounts of memory and SSD. There can also be variants with or without Wi-Fi, which is simply a small M.2 card mounted in a standard place in the computer.

My tested model has an Intel Core i5-12500T, which is a more energy efficient version of the “regular” i5-12500, 16GB RAM, and 256GB SSD. It’s one of the cheaper variants. It’s also available with 8GB of RAM, but I wouldn’t recommend that. A few hundred dollars for twice as much is well worth the money.

Performance is good, but not great. The processor’s six cores are good at pushing individual cores high for short periods of time, but do not do so well for high continuous loads. This results in high Geekbench results and lower Cinebench scores in my measurements. It matches the experience when I use the computer. Editing and cutting a video project is smooth and seamless even with lots of effects and short sequences with many layers, but it takes longer to export the result.

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HP Pro Mini 400 G9: Design

The Pro Mini 400 is a flat little box, measuring just over 17x17cm wide/deep, and less than 4cm thick. It’s designed to stand on a table or hang on the back of a computer monitor. HP also sells mounting kits for it as an accessory, but doing so is a bit impractical, as all the connections are deep into the back of the monitor and it’s only suitable for selected HP monitors.

Mattias Inghe

On a table, it’s discreet and stands firmly on rubber feet, though it’s not the most attractive thing in the world. A black, flat aluminum tube with connectors and cooling grids on the flat front and back. Built more for practicality than ornamentation, you get plenty of fast USB ports and headphone jacks readily available in the front panel.

There’s also a small speaker, which the computer has as a backup if you don’t have any other audio device connected via headphones, USB, or screen. It doesn’t sound great, but it’s better than you’d expect and can be used in emergencies to hear what’s being said in video meetings or to play system sounds and videos. But we’d recommend connecting a headset or external speakers instead.

You get plenty of connections on the front and back of the device, and you won’t need a USB hub anytime soon. Mostly USB-A, but also a USB-C. One port on the front and one on the back has a power supply to charge your mobile phone, for example.

HP Pro Mini 400 G9: Easy to open

The top can be loosened and removed with a screw on the back for upgrades and maintenance. Not that there’s much to do once you’re inside. There’s a free SO-DIMM slot for inserting extra memory, but that’s it. If you want to expand the storage, you’ll have to replace the entire SSD with a larger one. But at least the SSD is easy to access unlike the memory that’s hidden under the system fan.

According to unconfirmed information, it should be possible to install a 2.5-inch disc in the computer, but there’s no internal SATA port. Is it worth the hassle? No, connect more storage on USB instead. It works perfectly well.

HP gets a gold star for an ambitious attempt to keep the fan noise down despite a powerful desktop processor. It has some active cooling at all times, but it’s almost impossible to hear it when it’s switched on but passive. And full load of the processor doesn’t pull up the RPMs so much that they’re distracting.

Mattias Inghe

HP Pro Mini 400 G9: Cooling

One reason for its limited performance in certain situations may be that HP has chosen subdued cooling over continuous maximum load. On the other hand, the computer often gets a clear buzzing tone at medium load that can be a bit annoying, but I’ve heard worse.

You can still buy the HP Pro Mini 400 G9 with Windows 10 Pro, which Microsoft still allows for business computers. Then you get a free upgrade to Windows 11 Pro if you want it. However, you can’t go back to Windows 10 Pro again if you change your mind.

My test sample had already made the switch to Windows 11, so I couldn’t go on a nostalgia trip. I recommend that individual users stick with Windows 11 for future compatibility and updates. Microsoft is phasing out support in 2025. You won’t have any bloatware except for some unnecessary things that always come with Windows. The only things HP adds are occasional apps that control specific hardware as well as support features and a digital manual.

HP Pro Mini 400 G9: Rating: 3 out of 5

HP Pro Mini 400 G9: Specifications

Product Name: HP Pro Mini 400 G9
Tested: January 2024
Manufacturer: HP
Tested model: 6B2D9EA#UUW
Processor: Intel Core i5-12500T, 6pcs P-core 2-4.4 GHz
Graphics: Intel UHD Graphics 770
Memory: 16GB DDR4
Storage: 256GB
Expansion slots: 1 SO-DIMM
Connections: USB-C 20 Gbit/s, 2pcs USB-A 10 Gbit/s, headset front. USB-A 3 10 Gbit/s, 2pcs USB 2.0 5 Gbit/s, lan, 2pcs DisplayPort, HDMI rear.
Wireless: Wi-Fi 6e, Bluetooth 5.2
Operating system: Windows 11 Pro (pre-installed with Windows 10 Pro downgrade)
Other: Speakers
Noise level: 27-35 dBa
Size: 17,7 x 17,5 x 3,42 cm

HP Pro Mini 400 G9: Performance

Cinebench R23, cpu all cores: 7,834 points
CinebenchR23, cpu single core: 1,396 points
Geekbench 6, cpu all cores: 7,122 points
Geekbench 6, cpu single core: 2,286 points
Geekbench 6, graphics: 7,001 points
Disk read: 3,163.23 MB/s
Disk write: 1,920.2 MB/s