Minisforum UM870 Slim Review (2026)

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The Minisforum UM870 Slim is a 0.829 L Ryzen 7 8745H mini PC with two PCIe 4.0 M.2 slots, and the mini PC reviews hub compares machines like it on the published figures that decide whether they belong on a shelf: idle watts, sustained package power and noise. On those numbers, the Slim lands well. On the name, it needs a correction first.

There is no standard-size "UM870" for this machine to be slimmer than. Minisforum's current catalog and support pages list the UM870 Slim and the UM870 Plus, and retailers routinely shorten "UM870 Slim" to "UM870" — which is where the phantom base model comes from. The genuine sibling is the Plus: identical Ryzen 7 8745H, identical official 130 × 126.5 × 50.4 mm chassis, identical memory and storage layout, plus OCuLink. There is also no 8845HS version of the Slim in Minisforum's official specification. The documented chip is the 8745H; the 8845HS lives in adjacent models such as the UM880 family.

This review works through what the 8745H and Radeon 780M actually do when the machine never sleeps: idle draw from two independent test setups, sustained power and package temperatures, the memory-population question that decides whether the integrated GPU runs at design bandwidth, and what one Ethernet port and no SATA bay mean for Proxmox, Jellyfin, Home Assistant and NAS duty. For where this box sits against the rest of the lineup, the Minisforum brand guide maps the whole catalog.

It is aimed at self-hosters who want Zen 4 cores, all-flash storage and single-digit idle watts in a small chassis — and who can live without dual Ethernet, OCuLink and internal 2.5-inch drives.

Quick verdict. The UM870 Slim is a dual-NVMe Zen 4 box that idles in the single-digit watts in one test setup, holds roughly 3.8 GHz through long sustained load in another, and gives the Radeon 780M enough bandwidth to do real media work — provided two matched DIMMs are actually populated. It is not a dramatic downsizing, it has exactly one Ethernet port, and its MediaTek wireless card is the single component most likely to send a Linux user shopping for a replacement.

→ Check the current price on Amazon

UM870 Slim — Overview and First Impressions

Minisforum launched the Slim in China on November 4, 2024, with barebone, 16 GB + 1 TB and 32 GB + 1 TB configurations, and global availability followed later that month. The retail picture has never been tidy: regional Minisforum stores have exposed different bundle mixes, and the Amazon variation family currently carries a barebone listing, a 16 GB + 512 GB configuration and a 32 GB + 1 TB configuration. Whatever the listing says, the parts that matter are the CPU and the installed module count.

That CPU is the Ryzen 7 8745H — eight Zen 4 cores, sixteen threads, up to 4.9 GHz. It is effectively a Hawk Point-class part closely related to the Ryzen 7 8845HS, minus the 8845HS's XDNA NPU. That distinction matters for anyone reading "Ryzen AI" into a spec sheet: a 16-TOPS NPU is not part of this chip, and local LLM work here runs on CPU and the Radeon 780M's compute units, not on an NPU-only path. Relabeling the machine as a 8745HS or 8845HS system is simply a specification error.

The "Slim" label also deserves to be deflated rather than sold. Against the UM790 Pro's 130 × 126 × 52.3 mm chassis, the Slim saves 1.9 mm of height and roughly 3.3% of volume — 0.829 L versus about 0.857 L. That is thinner, not dramatically smaller, and machines such as the GEEKOM A8 and GMKtec K6 have occupied comparable or smaller footprints. The honest framing is that Minisforum kept its standard footprint and simplified the I/O: one USB4 port instead of two, a single 2.5GbE port, and no OCuLink.

What the Slim does keep is the part that matters for a hypervisor host: two full M.2 2280 PCIe 4.0 ×4 slots fed by the Ryzen 7040-class platform, in a package that independent testing has measured idling as low as 5.2 W at the wall.

Specs and What's in the Box

The port inventory is deliberately narrow. On the rear and sides you get HDMI 2.1 FRL, DisplayPort 1.4, one USB4 40 Gbps Type-C, two USB-A 3.2 Gen 2, two USB-A 2.0, a 3.5 mm combo jack and one 2.5GbE RJ45. Minisforum's own product page carries a stray marketing sentence about a "5G wired network port" and link aggregation; the specification table lists a single 2.5GbE RJ45, and the hardware follows the table. There is no second NIC to aggregate.

The 2.5GbE controller is a Realtek RTL8125, identified in teardown. That is a perfectly ordinary choice for a client or server host, and a less comfortable one for a firewall appliance — which is a topology question rather than a silicon defect, and it comes up again below.

Wireless is supplied by an M.2 2230 card that teardown identifies as the MediaTek MT7902, with Wi-Fi 6E and an official Bluetooth 5.2 specification. Third-party teardown has described the module as Bluetooth 5.3-capable, but 5.2 is the number Minisforum publishes, and that is the number to plan around.

Display support reaches up to three outputs through HDMI 2.1, DisplayPort 1.4 and USB4, with official support for 8K60 or 4K120 signaling where the attached display chain allows it — signaling ceilings, not a claim about what the 780M can render. Power comes from an external 120 W brick rated at 19 V / 6.32 A, and the box ships with the adapter and cable, an HDMI cable, VESA/wall-mount hardware and a manual.

Storage is where the platform is more generous than its price tier usually allows. Both M.2 positions are 2280-length, PCIe 4.0 ×4, and there is no 2.5-inch SATA bay anywhere in the chassis. Minisforum publishes "up to 4 TB" without breaking that figure down per slot, so 4 TB is the capacity the vendor stands behind; the board itself exposes two full-width Gen4 connectors.

Configured systems ship with Windows 11 Pro. A barebone purchase includes the chassis, board, CPU and cooling, and requires DDR5 SO-DIMMs, at least one NVMe drive and an operating system before it will POST.

Build Quality and Durability

At 130 × 126.5 × 50.4 mm and 0.67 kg, the Slim is a dense little box rather than a large one, and its cooling stack is the reason. Minisforum fits a large system fan, three copper heatpipes and phase-change thermal material, and routes airflow over the memory and storage as well as the APU. The company markets stable 65 W operation as the design target, and the independent load measurements back that up as a realistic sustained envelope rather than a burst figure.

Absent a 2.5-inch bay, the machine is all-flash by design. That is the right architecture for a hypervisor node and the wrong one for anyone who wants four spinning drives in the same enclosure — a distinction that separates it cleanly from the NAS-oriented designs in our best mini PC for NAS roundup.

Firmware is the weak spot in the ownership experience. Minisforum support exposes BIOS V1.09 for the model, with no useful public changelog, and independent testing found no meaningful user-facing fan-curve or performance-mode control in the BIOS. In practice that means cooling behavior is set by the embedded controller and by how the enclosure is mounted. The included VESA bracket is useful, but mounting the machine flat against a panel with the rear exhaust blocked will cost sustained clocks — leave the exhaust side clear.

Two physical details are worth planning around before purchase. The chassis provides its own M.2 cooling arrangement, so drives should be bought without integrated heatsinks; a tall aftermarket sink is more likely to foul the lid than to help. And the Wi-Fi card sits in a standard M.2 2230 Key-E slot, which makes it a replaceable part rather than a fixed one.

Performance — Sustained Clocks, Idle Watts and Memory Bandwidth

Sustained power and thermals

Two independent test setups frame the load behavior, and they disagree in the useful way. In one stress scenario the machine peaked at 86.1 W at the wall with a 73.7 W average and a maximum CPU temperature of 88.1 °C; in a heavier scenario it averaged 81.3 W, peaked at 93.3 W and topped out at 81 °C. The second setup recorded a brief full-load excursion near 95 W that settled around 89 W, and roughly 83 W after more than fifteen minutes of sustained load, with the CPU holding around 3.8 GHz, CPU temperatures at or below 89 °C and GPU temperatures at or below 77 °C.

Read together, those figures describe a machine that dissipates around 80 W continuously without collapsing. Nothing in the long-duration data supports the idea that the Slim chronically throttles — the clocks hold and the temperatures plateau rather than climb.

Noise is similarly restrained. At a 40 cm measuring distance, one test recorded a 33.2 dBA room baseline, 34.1 dBA at idle and 38.2 dBA under load. That is audible in a quiet room during sustained work and effectively inaudible when the machine is idling, which is the state a home server spends most of its life in.

Idle power, and why the two numbers differ

Idle consumption is the headline for always-on duty, and the two credible measurements are 5.2 W and roughly 13 W at the wall. That spread is not a contradiction; it reflects different configurations, peripheral loads, power-management settings and test protocols. Both numbers are real, and neither should be treated as an invariant specification of the model.

The practical implication is simpler than the spread suggests. A machine in this class sitting in the single-digit-to-low-double-digit watt band is economical to leave running, and the delta between the best and worst measurement is roughly the delta between one efficient business Tiny and another. Running the arithmetic on a constant load — watts multiplied by 8.76 gives annual kilowatt-hours — a 10 W difference is about 87.6 kWh per year. Both measurements land the Slim on the right side of that line.

Memory bandwidth and the 780M

The Radeon 780M has no dedicated VRAM. It draws on the same DDR5 the CPU uses, which makes dual-channel operation a performance decision rather than a capacity decision. Two matched SO-DIMMs at DDR5-5600 feed the iGPU substantially more bandwidth than a single module of the same total capacity.

That matters because Minisforum's configured bundles are sold by capacity, not by population. At least one owner has reported receiving a 32 GB configuration populated as a single 32 GB module rather than 2× 16 GB. Verify the module count on arrival, and treat any "32 GB" listing as unverified until the actual DIMMs are visible — a single-stick 32 GB build concedes iGPU bandwidth for nothing.

The paired rule also applies in the other direction: going from 32 GB to 64 GB or 96 GB does not make the 780M faster when the workload already fits in memory. Capacity buys VM density. Bandwidth buys graphics and tone-mapping headroom. They are different purchases.

Storage and the media engine

Two PCIe 4.0 ×4 M.2 slots are the most homelab-relevant feature on the board. Splitting the hypervisor boot volume, VM datasets and transcode scratch across two drives is a real architectural improvement over a single-slot machine, and it costs nothing in chassis volume. It is not redundancy — a mirror is not a backup, and neither is a faster drive.

For media work, the 780M's VCN generation covers hardware H.264 and HEVC decode and encode, including 10-bit HEVC, plus AV1 decode and encode on this Ryzen mobile generation. Jellyfin supports AMD acceleration through VA-API on Linux and AMF on Windows, and AMD does not impose the fixed concurrent-encode-session cap that consumer Nvidia cards carry.

The closest verified capacity reference is a community test on a different machine with the same 8845HS and Radeon 780M pairing: approximately eight simultaneous 80–100 Mbps 4K remux streams transcoded to 720p with tone mapping disabled, plus mixed 1080p and 4K sessions beyond that. That is a same-iGPU-class proxy, not a UM870 Slim measurement, and it should be read as evidence of capability rather than a guaranteed ceiling. HDR tone mapping, subtitle burn-in and audio conversion all shift work off the media engine, and some distribution Mesa builds ship H.264 and HEVC VA-API support disabled — the software stack causes more failed transcodes than the silicon does.

UM870 Slim vs UM870 Plus vs GMKtec K8 Plus — Head-to-Head

The first comparison is the one the name invites, and it is decided entirely by one connector. The UM870 Plus uses the same processor, the same official dimensions and weight, the same memory and storage layout and the same single 2.5GbE port — and adds OCuLink. Since OCuLink carries a direct PCIe 4.0 ×4 link with far less protocol overhead than tunneling a GPU over USB4, the Plus is the rational choice for anyone whose long-term plan involves an external desktop GPU. Minisforum does not make the Plus physically larger, so there is no size penalty to weigh.

The second comparison is the homelab one. The GMKtec K8 Plus is a little bigger at roughly 0.957 L, and for that volume it returns dual 2.5GbE, dual USB4 and OCuLink on top of the same dual-NVMe, dual-SO-DIMM layout. If the machine is going to be a virtualization host with separate storage and management networks, or a converged router-and-services box, the Slim's single NIC is the binding constraint and the K8 Plus resolves it. It is also the platform those eight-stream 780M transcode figures came from.

The historical comparison is the most deflating. The UM790 Pro is 1.9 mm taller and about 3.3% larger, and it shipped with two USB4 ports and a Ryzen 9 7940HS. The UM780 XTX is in the same footprint class and offers dual 2.5GbE, dual USB4 and OCuLink. Against both, the Slim trades connectivity for a marginal reduction in height.

The closest like-for-like competitor is the Beelink SER8, which sits at roughly 0.814 L with the same one-NIC, one-USB4, no-OCuLink philosophy and a similarly dual-NVMe layout. Both machines are targeting the same buyer.

Recommended Upgrades and Accessories

Memory — the one upgrade that changes behavior. The Slim wants two matched DDR5-5600 SO-DIMMs, and any purchase that does not deliver them is a downgrade disguised as capacity.

• Crucial DDR5-5600 2× 8 GB (16 GB total) — Check Price on Amazon
• Crucial DDR5-5600 2× 16 GB (32 GB total) — Check Price on Amazon
• Crucial DDR5-5600 2× 32 GB (64 GB total) — Check Price on Amazon

32 GB is the practical starting point for a Proxmox host running several moderate VMs alongside containers and a media service. 64 GB is the right tier when memory — not CPU — is what limits how many guests you can run. The 96 GB official ceiling leaves headroom above all three kits for higher-density modules, but nothing about Plex, Home Assistant or Jellyfin alone justifies the 64 GB tier.

Storage — a second drive, for separation rather than speed. Both M.2 slots are PCIe 4.0 ×4, so a Gen4 drive will run at full link speed, but the useful move is dedicating one drive to the hypervisor and VM datasets and the other to media or scratch. Buy the non-heatsink version of either.

• Samsung 990 PRO 2 TB (non-heatsink) — Check Price on Amazon
• WD_BLACK SN850X 2 TB (non-heatsink) — Check Price on Amazon

Wireless — an Intel card if the machine runs Linux. The MediaTek MT7902 is the most actionable complaint in owner reports, and the standard remedy is an Intel AX210 in the same M.2 2230 Key-E slot. Windows has no particular problem here; Linux distributions have historically varied in how automatically the MT7902 comes up, and a test on Ubuntu reported working video, audio and wired Ethernet with no automatic wireless initialization. Support has been improving, so this is a friction issue rather than a permanent incompatibility.

• Intel AX210NGW M.2 2230 replacement card — Check Price on Amazon

Bulk storage — external, because there is no SATA path. With no internal 2.5-inch bay, capacity beyond the two M.2 slots comes over USB4. A 40 Gbps USB4 enclosure is fast enough to serve as a media library or backup target, and it is the only expansion route the chassis offers. Keep in mind that direct-attached storage over USB is not a RAID array and is not a backup; it is a shelf for data that lives somewhere else too.

One upgrade not to bother with. Thermal paste replacement is not a routine fix here. The stock cooling is a fan, three heatpipes and phase-change material, and the sustained measurements show it working. Abnormal temperatures are worth investigating; a healthy 80 W load is not a reason to open the case.

Who Should Buy the UM870 Slim?

As a Proxmox or virtualization host

This is the machine's best use case. Eight Zen 4 cores, 96 GB of supported memory and two Gen4 M.2 slots in a 0.83 L chassis that idles in the low single digits to low double digits is exactly the shape of a compact lab node, and owners have run Proxmox on it. The virtualization stack on AMD hardware is AMD-V/SVM for CPU virtualization and AMD-Vi/IOMMU for device assignment — the terminology differs from Intel's VT-x and VT-d, and firmware settings differ accordingly.

The caveat is that exact IOMMU grouping for the production board has not been documented, so clean passthrough of every device cannot be promised in advance. Validate the specific PCIe device and BIOS combination before committing to a passthrough-dependent design. The best mini PC for Proxmox roundup covers the platforms where that topology has been mapped.

As a Jellyfin or Plex server

Yes, with two conditions. Populate both DIMMs, because the 780M shares system memory. And accept that AMD media acceleration on Linux lives or dies by the software stack — VA-API drivers, Mesa packages and container permissions. Jellyfin's AMD path is well supported when configured correctly; Plex's track record with 780M hardware transcoding varies more with version, client and tone-mapping behavior. Intel Quick Sync remains the lower-friction choice for a dedicated Plex box, and our Plex minimum requirements breakdown covers where a low-power Intel system wins outright.

As a Home Assistant box

Substantially more CPU than Home Assistant needs. That is not a criticism — it is the point of running HA as one workload among many on a host that also carries Jellyfin, a NAS share or a couple of containers. Low idle draw, NVMe storage and available RAM make it a sensible consolidated node rather than a dedicated appliance.

As a router or firewall

Not without a plan. A single 2.5GbE port means either a VLAN-on-a-stick topology with a managed switch, or a USB NIC. The first is a legitimate design; the second adds a driver and reliability layer that has no place in front of the household's internet connection. If pfSense or OPNsense is the goal, buy a machine with two physical NICs — the K8 Plus in the table above is the natural candidate, and the single-NIC failure mode is documented across the platform's owners.

As a NAS

The two NVMe slots make an excellent all-flash server node. They do not make a NAS: there is no SATA bay, no drive caddy and one 2.5GbE port. Attaching a USB4 enclosure turns it into a host with a large cabinet, not a storage appliance. If multi-disk storage is the requirement, the NAS picks are the right starting point.

As an eGPU platform

USB4 works, with the usual tunneling overhead and firmware variability. OCuLink does not exist on the Slim, and the UM870 Plus — same chassis, same weight, same everything else — is where that port lives. For a first homelab build, the starter guide covers how to sequence storage, networking and services before spending on expansion.

Frequently Asked Questions

Conclusion and Final Verdict

The UM870 Slim is a good machine wearing a slightly misleading name. It is not a dramatic reduction of anything — 1.9 mm and about 3% of volume against the UM790 Pro — and the actual sibling relationship is with the UM870 Plus, which shares the chassis and adds OCuLink. Judged on its own terms, though, it does the thing a compact hypervisor node needs to do: eight Zen 4 cores hold sustained clocks around the 80 W envelope, the box idles in the single digits to low double digits at the wall depending on configuration, noise stays in the high 30s dBA under load, and two full-width Gen4 M.2 slots make storage separation possible without external hardware.

The compromises are equally clear and they are all I/O. One 2.5GbE port rules out a conventional firewall deployment and makes a separate management network a VLAN exercise. There is no SATA bay, so bulk storage means USB4 or another machine. There is no OCuLink, so external GPU work goes through USB4 or up to the Plus. And the MediaTek MT7902 is the component most likely to generate a support thread on Linux, with an Intel AX210 as the standard remedy.

Buy it if you want a low-idle, all-flash Proxmox or Jellyfin node with real memory headroom and you can work within a single NIC. Buy the UM870 Plus if eGPU expansion is on the roadmap, the GMKtec K8 Plus if dual Ethernet and dual USB4 are worth roughly 0.13 L of extra chassis, and a dual-NIC design outright if the machine is going to be the router.

For where the UM870 Slim lands against the rest of this year's shortlist, see the mini PC reviews hub, the best ultra-compact picks if volume is the priority, and the price guide for how configured bundles and barebone builds compare once memory and storage are included.

→ Check the current price of the UM870 Slim on Amazon