Lumen Three | RTX 5080 + Ryzen 7 7800X3D | Ready-to-Go Gaming PC | PC36

🌅 Lumen Three

The smallest thing on the desk, and the fastest thing in the room

Every builder has a version of this machine: an RTX 5080, a quick processor, and a full tower to put them in. Lumen Three is that performance in a case the size of a hardback book, in anodised aluminium and solid walnut with no lighting at all. It is a flagship you can leave in a living room.

Doing that properly is harder than it sounds. A 5080 produces around 360W of heat. In a full tower that is a fan curve. In 10.4 litres it is a design problem, and the answer is not to force a big card into a small box and hope. It is to choose a slimmer 5080 that leaves the Terra's internal spine where the cooler needs it, pair it with a processor that runs cool for its speed, and pull heat out of the base rather than letting it sit. Every part on this list is chosen with the two either side of it in mind.

What you end up with is genuine 4K performance from a machine most people would not pick out as a PC at all.

🧬 Built to last, designed to evolve

This system is built on AMD's latest AM5 platform, which offers one of the best upgrade paths available today. That means you can start with a great processor now and still have room to move up the stack later, while keeping the same motherboard, case, power supply and most of your core components. Graphics card, storage and cooling all remain straightforward to change later, within the space limits any small form factor build has.

📃 Specifications

• 🧠 CPU: AMD Ryzen 7 7800X3D
  Click or tap for deeper spec info

  • 8 cores, 16 threads of Zen 4 with 96MB of L3 cache, courtesy of AMD's 3D V-Cache stacked directly onto the compute die
  • The chip that made X3D the default recommendation for gaming. That cache means the processor spends far less time waiting on memory, and it shows up in frame times rather than just benchmark averages
  • It is here rather than something newer for a specific reason: it draws well under 100W in games while performing like a chip that draws far more. In a case already dealing with a 360W graphics card, a processor that adds very little to that total is worth more than a few percent of extra frame rate
  • The 9800X3D is available as an upgrade, with a caveat worth reading before you take it. See the upgrade options below
• ❄️ CPU cooler: Thermalright AXP120-X67
  Click or tap for deeper spec info

  • A low-profile top-down cooler, 67mm tall, with six heatpipes and a full-size 120mm fan. Small form factor coolers are usually a compromise. This one genuinely is not
  • The 120mm fan is the point. A larger fan moves the air a 7800X3D needs while turning slowly, and fan speed is what you actually hear. Most coolers at this height use a 92mm fan and have to spin it hard to keep up
  • Top-down rather than tower, so it also pushes air across the motherboard's power stages and memory, which in a case with no through-draught is worth having
  • Its 67mm height is what sets where the Terra's spine sits, which in turn determines how thick a graphics card will fit. That relationship is why the card on this build is chosen the way it is
• 🔲 Motherboard: ASRock B850I Lightning WiFi (Mini-ITX)
  Click or tap for deeper spec info

  • 12 phase power design with ten 110A SPS stages on Vcore, giving around 1,100A available to the processor. Plain English translation: this is desktop-tower power delivery on a 17cm square board, and it is far beyond anything AM5 can draw. Nothing you fit here will ever be limited by the motherboard
  • PCIe 5.0 x16 for the graphics card, which is the interface the RTX 5080 is built for
  • Two M.2 slots, the primary at PCIe Gen5 x4 and the second at Gen4 x4, so one stays free for a drive you add later
  • It ships with a thermistor cable, which is a small thing that matters a lot in this case. It lets us place a temperature probe where heat actually collects rather than relying on the CPU sensor alone, and drive the fan curve from that. In a chassis with no through-draught, tuning from the right measurement is most of the job
  • Wi-Fi 6E with 160MHz channels, Bluetooth 5.2, and Killer E3100G 2.5 Gigabit Ethernet
  • Realtek ALC1220 audio, which is a genuine step above the codec normally fitted at this board size
  • Two DDR5 slots, as every Mini-ITX board has. Both are used by the memory fitted, so a capacity upgrade later means replacing the kit rather than adding to it
  • PC36 only uses motherboards chosen for stability and longevity. See our Trusted brands page
• 📏 Memory / RAM: 32GB (2×16GB) DDR5-6000 CL36
  Click or tap for deeper spec info

  • EXPO-tuned dual channel DDR5-6000 CL36, the speed and timing combination Ryzen responds to best on AM5. We fit CL36 as standard rather than the slower CL40 kits often used at this price
  • 32GB is comfortable headroom for gaming, streaming and creative work at the same time. If you do heavy 3D or video work alongside your games, the larger options below are worth a look
  • Both memory slots are used, since Mini-ITX boards have two. A larger kit is cheaper chosen now than swapped later
  • Specification guaranteed, model may vary. Happy to confirm the exact part on request
• 💾 Storage: 1TB NVMe PCIe 4.0 SSD (TLC)
  Click or tap for deeper spec info

  • TLC flash rated at 6,500MB/s or better, which holds its speed through long sustained writes rather than dropping off once a cache fills. On a build at this price we do not fit QLC drives
  • Higher write endurance than the entry-tier alternative, which matters if you record gameplay at 4K, edit video, or install and uninstall a lot
  • The second M.2 slot sits free, and the case also takes two 2.5 inch SATA drives, so adding storage later is straightforward
  • Specification guaranteed, model may vary. Happy to confirm the exact part on request
• 🎮 Graphics card: NVIDIA RTX 5080 16GB
  Click or tap for deeper spec info

  • The card arrives fitted, because in this chassis it is safer that way. It is mounted vertically on a riser against the side panel and supported along its length rather than cantilevered off the motherboard, so it travels as built. Nothing to install, nothing to unbox and align, no thermal paste to worry about
  • Genuine 4K ultra performance in modern AAA titles, with the ray tracing hardware and DLSS 4 multi frame generation to keep path-traced games playable rather than theoretical
  • 16GB of GDDR7 on a 256-bit bus, feeding textures fast enough that 4K stops being the thing limiting your settings
  • We fit a slimmer 5080 here specifically, and it costs us more than the fat triple-slot models most builds use. That is the trade this case demands: the card has to leave room for the spine to sit where a 67mm cooler needs it. A cheaper, thicker 5080 would either not fit or would force a worse cooler above it. Worth knowing if you ever plan to change the card yourself, so measure first and talk to us before you buy
  • The chipset and VRAM are guaranteed: it will always be an RTX 5080 with 16GB. The AIB brand varies with availability, and we only use established manufacturers. See our Trusted brands page for more info
• 🧰 Case: Fractal Terra - Silver
  Click or tap for deeper spec info

  • 10.4 litres. Anodised aluminium throughout, an 8mm thick machined aluminium front, and a solid FSC-certified walnut panel. 343mm wide, 218mm tall, 153mm deep
  • The clever part is the spine: a stepless sliding central wall that moves through 30mm, letting you trade graphics card width against CPU cooler height. Up to 77mm of cooler one way, a much fatter graphics card with 48mm of cooler the other
  • On this build that adjustment is doing the most work it does anywhere in our range. A 5080 and a 67mm cooler is close to the limit of what 10.4 litres will take, and getting it right is a matter of millimetres rather than approximations
  • Supports graphics cards up to 322mm long, and two 2.5 inch drives
  • Small form factor builds take considerably longer to assemble and cable than a standard tower. That work is included in the price rather than added to it
• 🌬️ Case cooling: 1 × 120mm base exhaust fan with protective grille, plus full-area perforated side panels
  Click or tap for deeper spec info

  • The Terra has a single 120mm mount in the base and on this build it is not optional. With a 360W graphics card in the chassis, actively pulling heat out of the underside is the difference between a machine that holds its clocks and one that does not
  • We fit a grille over that fan as standard. In a chassis this tight the base fan sits exactly where loose cable ends want to fall, and a blade catching a cable is the kind of fault that is entirely preventable. It costs us a few pounds and it is not something you would ever have to think about
  • Both side panels are perforated across their full area, sitting directly alongside the graphics card, so the card draws cool air straight through the panel beside it rather than along a duct
  • Fan curves are tuned manually before dispatch using the board's thermistor probe as well as the CPU sensor, then verified through our standard stress testing rather than assumed
  • Being straight about expectations: this is a 4K machine in 10.4 litres. Under a sustained heavy load it is audible. It is well cooled, it holds its performance, and it is quiet at idle and in lighter games, but it is not silent when you are asking everything of it. Anyone who tells you otherwise has not built one
• ⚡ Power supply: Thermaltake Toughpower SFX 850W 80+ Gold, fully modular
  Click or tap for deeper spec info

  • SFX form factor, because that is what a case this size takes. An SFX unit is roughly half the volume of a standard ATX supply and costs more for the same wattage, which is one of the hidden expenses of building small
  • 850W rather than the 750W used lower in this series, because a 5080 draws around 360W on its own and spikes above that. This keeps the unit comfortably inside its efficient band under a full combined load rather than at the top of its range
  • Fully modular, which matters far more here than in a big case. In 10.4 litres there is nowhere to hide a cable you are not using, so every one left in the box is one less thing obstructing airflow
  • 80 PLUS Gold rated
• 🔌 Cabling: Black cabling, routed for a small chassis
  Click or tap for deeper spec info

  • Black cables throughout. The Terra has no glass panel, so nothing here is on display and the cabling is optimised for airflow and serviceability instead of looks
  • Cable routing is the hardest part of a build like this and it is where most of the assembly time goes. Done badly it blocks the airflow the whole design depends on, and on a build with a 5080 in it there is no slack in that budget
  • White internal components are available on request. Ask us on live chat before you order and we will price it up
• 📶 WiFi / Bluetooth / Ethernet: Wi-Fi 6E, Bluetooth 5.2 and Killer 2.5 Gigabit Ethernet, included
  Click or tap for deeper spec info

  • Built into the ASRock B850I Lightning WiFi. No separate adapter needed, and the aerial is supplied in the box
  • Wi-Fi 6E with 160MHz channel support, which adds the 6GHz band. That is usually far less congested than 2.4 and 5GHz if your router supports it
  • Killer E3100G 2.5 Gigabit Ethernet for a wired connection, which we would still recommend for competitive play
• 🪟 Operating system: As chosen by you from the listing options below. Windows 11 Home (OEM) is recommended.
• 🧹 Setup and optimisation: PC36 High-Class Standard. Full stress test with certificate, bloat-free installation, and BIOS set up properly
  Click or tap for deeper spec info

  PC36 High-Class Standard, included free with every build

  • Ready the moment you open the box. Your PC boots straight into Windows with a local account already set up. No account sign-in wall, no first-run questionnaire, no half-hour of setup before you can use the machine you just bought
  • BIOS updated and configured properly: manual fan curves, PBO enabled, EXPO/XMP enabled, Secure Boot enabled
  • Vanilla Windows 11 installation if you choose Windows, with no bloatware added by us, and all drivers loaded and ready to go
  • Full stress test with certificate. Every system is torture tested on CPU, RAM and GPU before dispatch, and ships with the certificate to prove it

  PC36 Premier Optimisation, available in the listing options

  • CPU tuning to bring thermals and noise down with minimal performance loss, plus a deeper strip and debloat of Windows
  • This is the option we would recommend on this build above any other, and it is the one that matters most on the whole listing. A 5080 in 10.4 litres has no thermal headroom to waste. The 7800X3D responds very well to a Curve Optimiser undervolt, and every watt the processor does not draw is a watt the case does not have to shift for the graphics card. In a tower this is a nice-to-have. Here it changes what the machine sounds like

  PC36 Ultimate Performance Tune, available in the listing options

  • Advanced overclocking: RAM tune, CPU tune and GPU overclock on top of everything in Premier
  • Being straight about the ceiling. The 7800X3D is not overclocked by raising multipliers, since AMD limit voltage on the stacked cache for good reason. It responds to a per-core Curve Optimiser undervolt, which suits this case well. The GPU portion is where it differs from a tower: the 5080 in 10.4 litres is limited by the heat the case can remove, not by its clock ceiling, so pushing power upward returns less here than it would in a Luftstrom or an Ark. We will still do it properly if you want it, but Premier is the better value option on this specific machine
• 🛡️ Warranty: 3 years parts & labour (return to base)
  Click or tap for deeper spec info

  • Standard 3-year coverage included, parts and labour both
  • Optional extended warranties in the listing options below

👁️ Transparency notes

• Properly cooled and holding its clocks, but 360W of graphics card in 10.4 litres is audible under a heavy load (click or tap to read more)

  We would rather say that here than let you find out. At idle and in lighter games it is very quiet, and it holds its clocks throughout. If near-silence under full load is the priority, a Flux in the same price range will deliver it and a Terra will not.

• Small form factor systems run warmer, so we set a sensible thermal limit in the BIOS that costs nothing you would notice (click or tap to read more)

  On builds like this we typically set the CPU thermal limit to around 80°C in the BIOS. That is deliberate, it protects the machine, and it costs nothing you would notice in a game.

• Product images are representative photos of a similar spec in the same style. Your PC will look similar but not identical. Our support team can help clarify anything you're unsure of.
• Photos may show a cable tie holding the graphics card, which is deliberate, permanent and routed clear of every fan (click or tap to read more)

  A card of this size and weight will sag and sway at its outer end, and in a chassis this dense that movement is a real risk to the card and to the slot it sits in. The restraint stops it, and it is part of how we make a build like this safe to own and safe to move.

• Memory, SSD and graphics card carry a specification guarantee rather than a fixed model (click or tap to read more)

  Most parts are named models and will be what is delivered. RAM, SSD and graphics card instead carry a spec guarantee, because current market conditions make stock on those three very variable. This keeps us agile enough to offer good pricing and honest spec lists. If you want clarity on the precise models we will use, drop us a live chat on the day you're ready to purchase and we'll confirm it.

🛠️ Popular upgrade options

• Quick-add upgrades. This listing has a set of one-click upgrades chosen to fit this exact build, each one priced, in the Quick-add Upgrades section on this page. Memory, storage, optimisation, the anti-sag bracket and the extended warranty are in the build options instead. Anything not shown in either place, ask us on live chat and we will price it.
• CPU upgrade to Ryzen 7 9800X3D: choose it from the quick-add upgrades, or speak with us via live chat.
  Click or tap for more info

  Read this one before you take it. The 9800X3D is the faster processor and in a tower we would recommend it without hesitation. In this case it comes with a condition attached.

  Despite its improved physical design, the 9800X3D draws considerably more power than the 7800X3D and therefore runs hotter. In 10.4 litres, alongside a 5080, there is not enough thermal headroom to let it run unrestricted. We fit it with a power limit of roughly 80 to 100W PPT so that it stays within what this case can actually remove.

  What that means in practice: you still get the 9800X3D's larger cache and higher single-core ceiling in games, which is where most of its advantage lives. What you give up is the top end of its multi-core performance, so heavy rendering and encoding will not show the full gain you would see from the same chip in a tower. If gaming is the goal it is a worthwhile upgrade. If you bought this machine to render on, the honest answer is that a tower would serve you better than a faster processor in a small box.

• Need a monitor, keyboard or mouse? Scroll past the add to cart button. We've paired specific peripherals to get the best out of this build.
  Click or tap for more info

  This is a 4K machine. If you are pairing it with a 1440p panel you will still get very high frame rates, but you will not see what the graphics card is capable of. If the monitor is the older part of your setup, that is where the next money should go.

• Memory upgrade to 48GB or 64GB: available in the listing options below.
  Click or tap for more info

  Worth deciding now rather than later, because both slots are occupied and upgrading afterwards means buying a replacement kit. Worth it if you edit video, run virtual machines or work with large 3D scenes. For gaming, including modded gaming, 32GB is not the limit here.

• Storage upgrade to 2TB: available in the listing options below.
  Click or tap for more info

  Worth it for most people buying at this level. Modern AAA installs regularly run past 150GB each, and 4K capture fills a 1TB drive faster than you expect. Unlike the memory, this one you can defer, since the second M.2 slot is free.

• White internal components: available via live chat.
  Click or tap for more info

  The Terra's silver and walnut exterior suits white internals nicely, though with no glass panel you will only see them when the case is open. Ask us and we will price it up.

• Anything else: speak with us via live chat. This is the most constrained build we sell and also one of the most interesting. If you have something specific in mind we would much rather discuss it before you order than have you discover a limit afterwards.

🎯 What is this PC best for?

• 4K gaming at high to ultra settings in modern AAA titles
• 1440p at very high refresh, where the 7800X3D's cache sets the ceiling rather than the graphics card
• Ray tracing and path tracing with DLSS 4 multi frame generation
• Desks and living rooms where a full tower is not welcome, and where the machine is meant to be seen
• Buyers who want top-tier performance and have decided that size matters as much as speed

📊 Performance estimates

Figures are given at both 1440p and 4K. Performance varies with game updates, maps, settings and background apps. These are estimates, not guarantees.

Fortnite - Competitive Settings (click or tap to expand)

1440p: 320-410 FPS
4K: 195-255 FPS
Native testing (no upscaling or frame generation).

Cyberpunk 2077 - Ray Tracing Medium (click or tap to expand)

1440p: 135-175 FPS
4K: 88-118 FPS
Upscaling set to Auto (DLSS / FSR / XeSS based on GPU).

Battlefield 6 - High Settings (click or tap to expand)

1440p: 155-195 FPS
4K: 92-122 FPS
Native testing (no upscaling or frame generation).

DaVinci Resolve - PugetBench Standard (click or tap to expand)

Estimated score: 9,000-10,000

💬 Need help?

Not sure if this is the right spec for you? Ping us on live chat and we'll help you choose the perfect PC for your games, work and budget. You'll be talking to one of us, not a chatbot.