Lian Li SX Platinum 1200W SXP Compact ATX Form Factor Power Supply w/ 12V-2x6 Cable - ATX 3.1 & PCIE 5.1 Compliant - 140mm Fan - Full Modular - 10 Year Warranty - Black (SX1200P.B)
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AI Verdict
This 1200W ATX 3.1, PCIe 5.1 PSU with 100% Japanese 105°C capacitors and a 140mm depth is for compact, high-power builds.
This 1200W PSU is a strong fit for high-end systems needing ATX 3.1 and PCIe 5.1 compliance in a compact 140mm depth. Its 80 Plus Platinum efficiency and 100% Japanese 105°C capacitors ensure stable power delivery and durability for demanding components.
If you don't need 1200W, look for the 850W or 1000W versions in the same series to save on cost while retaining features.
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Pros
- 1200W output with ATX 3.1 and PCIe 5.1 compliance supports next-generation hardware.
- Compact 140mm depth allows for wider case compatibility, especially in smaller builds.
- Fanless operation up to 40% load ensures silent computing during light tasks.
- Built with 100% Japanese 105°C-rated capacitors for durability and stable performance.
- Includes a 12V-2x6 cable and up to five PCIe 6+2 connectors for multiple GPU configurations.
- Braided main cables with included cable combs contribute to a cleaner aesthetic and easier management.
Cons
- Some cables, specifically SATA and the 12V-2x6 to dual PCIe, use flat ribbon sleeving instead of braided.
- Publicly available Cybenetics certification details were not available at the time of a professional review, despite the 80 Plus Platinum rating.
- Maximum fan noise level of 39.9 dBA at full load might be audible in quiet environments.
Dimension Scores
Achieves 80 Plus Platinum certification (up to 94% efficiency at 50% load) and supports power excursions up to 200% of rated output, meeting ATX 3.1 and PCIe 5.1 standards.
Features fanless operation up to 40% load and uses a 140mm fluid dynamic bearing fan, contributing to quiet performance, though it can reach 39.9 dBA at max speed.
Constructed with 100% Japanese 105°C-rated capacitors (Rubycon/Nippon Chemi-Con/Nichicon) and comes with a 10-year warranty.
Fully modular design with flexible braided main cables and included cable combs, though some secondary cables are flat ribbon.
Best For
- High-performance PC builds requiring 1200W in a compact ATX form factor.
- Systems utilizing ATX 3.1 and PCIe 5.1 graphics cards, such as RTX 40-series.
- Users prioritizing quiet operation during low to medium system loads.
- Builds where cable aesthetics are important, thanks to braided main cables and combs.
Not Recommended For
- Budget-focused builds, given its Platinum efficiency and high wattage.
- Users who need full braiding on all modular cables, including SATA and secondary PCIe.
Watch Out For
- The 80 Plus Platinum certification is stated, but Cybenetics certification details were not publicly available at the time of a professional review.
- While main cables are braided, secondary cables like SATA and the 12V-2x6 to dual PCIe use flat ribbon sleeving, which might not match the aesthetic of the primary cables.
- The 140mm fan can reach a maximum noise level of 39.9 dBA, which some users might find noticeable under heavy load.
Full Specifications
| ASIN | B0FPCFQ8TP |
| Brand | Lian Li |
| Wattage | 1200 watts |
| Fan Count | 1 |
| Model Name | SX1200P.B |
| Form Factor | ATX |
| Item Weight | 7.09 pounds |
| Manufacturer | LIAN LI |
| Connector Type | PCI Express |
| Cooling Method | Air |
| Output Wattage | 1200 Watts |
| Item model number | SX1200P.B |
| Compatible Devices | Computer System, Graphics Card, Processor, Motherboard, Hard Drive, Optical Drive, RAM, Case, etc. |
| Product Dimensions | 5.91 x 3.39 x 5.51 inches |
| Item dimensions L x W x H | 5.91 x 3.39 x 5.51 inches |
What Buyers Say
Users frequently highlight the compact 140mm depth as a significant advantage for fitting into smaller cases, which is a common challenge for high-wattage PSUs. The fanless mode for loads under 40% is also consistently praised for maintaining quiet operation during everyday tasks. While the main cables are braided and come with combs, some users noted that SATA and other secondary cables are flat ribbon, which can be a minor aesthetic inconsistency. The overall power stability and use of Japanese capacitors are also recurring positive points.
“Finally, a 1200W PSU that actually fits in my small case without blocking airflow, but man, I wish ALL the cables were braided, not just the main ones!”
Common Praise
- Compact 140mm depth fits well in cases with limited PSU space.
- Fanless operation below 40% load results in silent performance for light computing.
- Stable power delivery with tight load regulation and good ripple suppression.
- High-quality 100% Japanese 105°C-rated capacitors contribute to durability.
- Braided main cables with included cable combs make builds look cleaner.
- ATX 3.1 and PCIe 5.1 compliance with a 12V-2x6 cable supports modern GPUs.
Common Complaints
- Some modular cables (SATA, 12V-2x6 to dual PCIe) are flat ribbon, not fully braided.
- Lack of public Cybenetics certification details at the time of review.
- Maximum fan noise of 39.9 dBA under heavy load could be audible.
Ownership Tips
- The fanless mode really does keep things quiet for most browsing and light gaming, the fan only kicks in during intense sessions.
- The compact size makes a huge difference for cable management in tighter ITX or mATX builds.
- The included cable combs are a nice touch, but you might want to buy extra braided extensions for the flat ribbon cables if you're super picky about aesthetics.
- The 12V-2x6 cable feels robust and handles my RTX 4090 without any issues.
Frequently Asked Questions
Is this power supply compatible with NVIDIA RTX 40-series graphics cards?
Yes, it is ATX 3.1 and PCIe 5.1 compliant and includes a 12V-2x6 cable, making it compatible with modern high-power GPUs.
Does this PSU operate silently?
It features a fanless mode up to 40% load for silent operation during light use. The 140mm fan activates above this threshold.
What is the warranty period for this power supply?
Lian Li provides a 10-year warranty for this power supply, covering parts and labor.
Are all the cables braided?
The main cables (24-pin, CPU, 12V-2x6 GPU) are braided and include cable combs. Other cables, such as SATA and the 12V-2x6 to dual PCIe, use flat ribbon sleeving.
What is the physical size of this power supply?
It has a compact ATX form factor with a depth of 140mm, a width of 150mm, and a height of 86mm.
Buying Guide
When you're picking a power supply, you're looking for something that can reliably feed all your PC's hungry components without breaking a sweat. Wattage needs to match your system's total draw, with some headroom. Efficiency ratings tell you how much power is wasted as heat, and modularity makes cable management way easier.
Wattage (e.g., 1200W)
This is the total power your PSU can deliver. Think of it like the horsepower of a car; you need enough to get your system running smoothly, especially if you have a powerful graphics card and processor.
80 Plus Platinum Certified
This certification indicates how efficiently the PSU converts AC power from your wall into DC power for your components. Platinum means less energy is wasted as heat (up to 94% efficient), which saves you a tiny bit on your electricity bill and keeps your PC cooler.
ATX 3.1 & PCIe 5.1 Compliant
These are the latest standards for power supplies, especially important for newer, high-power graphics cards. Compliance means it's designed to handle the transient power spikes these cards can demand, preventing system crashes.
Modular Design
A fully modular PSU means you only plug in the cables you actually need. This drastically reduces cable clutter inside your case, improving airflow and making your build look much cleaner, like organizing your closet so only the clothes you wear are visible.
Alternatives
If this 1200W unit is overkill or too expensive, look for a fully modular ATX 3.1 and PCIe 5.1 compliant PSU with a lower wattage (e.g., 850W or 1000W) and a similar 80 Plus Platinum or Gold efficiency rating.
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