ASRock Steel Legend SL-1200GW PSU Review

1. Introduction2. Bundle & Cabling3. External4. Internal5. Testing Methodology and Results6. Closing Thoughts7. View All Pages

Today we take a look at a new power supply that ASRock sent us for analysis – the company's latest Steel Legend SL-1200GW. This unit meets the latest ATX 3.1 and PCIe 5.1 specifications, while the 1000 and 1200W models in this range meet 80 Plus Gold and Cybenetics Platinum standards. ASRock ships these fully modular power supplies with a 10 year warranty.

ASRock seems to make these units in white coloured variants which will appeal to those builders creating a themed system. ASRock have partnered up with OEM HEC for the design of this unit, and it is fully modular, incorporates a fluid dynamic bearing (FDB) fan and adopts high grade Japanese capacitors throughout the design.

Specifications:

• 80 PLUS® GOLD Certified
• Cybenetics PLATINUM and LAMBDA A Certified
• ATX3.1 & PCIe5.1 Ready
• Fully Modular Cable Design
• Native 12V-2×6 Connector Dual Color Design
• 100% Highly Reliable Japanese Capacitors
• 135mm Striped Axial FDB Fan
• iCool Intelligent Fan Control Mode
• Built-in 5V BOOST function.

The ASRock SL-1200GW ships in a colour matched white box with a high resolution image of the unit on the front along with a list of key selling points, such as the 80 Plus Gold and Cybenetics Platinum certifications along with the ATX 3.1 and PCIe 5.1 compatibility.

The rear of the box expands on details such as the cabling, the efficiency chart, and a list of features.

Inside the box are two sections. These contain the power supply and some supporting literature on the power supply, alongside a cable bag with the accessories.

Inside the box there are some mounting screws, ties, some literature on the product, PSU tester, and a lovely white power cable – we don't often see those!

ASRock supplies a wealth of cables with this unit, as shown in the images above. These are white to match the power supply itself. The ATX connector is 590mm long, the 4+4 Pin EPS 12V cable is 640mm long and the 8-pin EPS 12V is also 640mm long. The 6+2 pin PCIe connectors are 650mm long and the SATA cables all have +120mm spacing between them. The gauge is between 16-18AWG with the PCIe 5.0 600W cable between 16-24AWG. The quality of the cables is pretty good throughout and none of them have in-cable capacitors installed, which is always good to see.

The ASRock Steel Legend SL-1200 is a reasonably small 1200W supply, measuring 150 x 85 x 150mm – this means it will fit into a huge variety of chassis designs. Some 1200W power supplies can be physically large which can limit their installation compatibility.

I have to admit I do like the styling of this power supply, it's a matte white which is certainly more eye catching that the plain matte black version. There are some nice stickers and layout decisions around the panels, although I do have to admit the ‘S' logo on the top of the unit, in the center of the fan, reminds me of the ‘Superman' logo a little.

If you pay close attention you will see the edges of this design are rounded and the mesh style grille looks great as well around it. We will take a closer look at the fan shortly when we open the supply.

The modular bay is split over two rows and it is clearly labelled for ease of installation.

The other side of the chassis is home to the power switch and connector, with a mesh grille to aid airflow. At the other side is a button to enable and disable the intelligent fan mode. This is something we have seen a lot of manufacturers adopt in recent years. Intelligent mode, we noticed, also seems to increase fan speed a little at higher load demands, which is interesting.

The power supply is able to deliver 100A across the +12V rail, and 25A across both minor rails. Total power output is set at 1200 Watts.

ASRock seem to be using a Globe fluid dynamic bearing (FDB) fan under their own label, with the ID RL4Z S132512EH-3M rated at DC 12V, 0.50A. We like FDB fans, they tend to last a long time and not make a lot of noise.

As we mentioned earlier in the review ASRock told us that they are partnered with HEC/Compucase for the design of this power supply, a company that has been around now for a very long time in the industry. The design of this unit is a half bridge LLC topology and incorporates four X capacitors, four Y capacitors and two filtering inductors. There are some rectifying bridges mounted on small heatsinks as well. Soldering quality throughout is pretty good, across the main PCB and daughtercards.

The primary capacitors of choice are Nippon Chemi Con – a 450V 560uF cap along with a 450V 460uF cap, for a total of 1020uF. Both caps are from their KHE and KMZ series and are both rated at 105C. On the secondary side of the unit there are six MOSFETs which generate the primary 12V rail. The 3.3V and 5V lines are generated from DC to DC converters mounted on a vertical daughtercard connected to the main PCB to save space. Caps in the secondary stage are from Nippon Chemi Con and Rubycon – both excellent Japanese manufacturers.

It ships with SCP, OTP, OPP, OCP, OVP and UVP protections in place.

Correctly testing power supplies is a complex procedure and KitGuru have configured a test bench which can deliver up to a 2,000 Watt DC load.

We test ambient temperatures at 35C in our environment to greater reflect warmer internal chassis conditions.

We use combinations of the following hardware:

• SunMoon SM-268
• CSI3710A Programmable DC load (+3.3V and +5V outputs)
• CSI3711A Programmable DC load (+12V1, +12V2, +12V3, and +12V4)
• Extech Power Analyzer
• Extech MultiMaster MM570 digital multimeter
• Extech digital sound level meter
• Digital oscilloscope (20M S/s with 12 Bit ADC)
• Variable Autotransformer, 1.4 KVA

DC Output Load Regulation
Combined DC Load	+3.3V		+5V		+12V		+5VSB		-12V
	A	V	A	V	A	V	A	V	A	V
120W	0.90	3.33	0.93	5.02	8.95	12.04	0.50	5.01	0.20	-12.01
240W	1.62	3.33	1.63	5.01	18.45	12.03	1.00	5.01	0.20	-12.01
600W	3.00	3.33	3.11	5.02	46.78	12.02	1.50	5.01	0.30	-12.01
900W	4.01	3.33	4.05	5.01	70.86	12.01	2.00	5.01	0.30	-12.00
1200W	5.02	3.33	5.20	5.02	94.57	11.99	2.50	5.01	0.30	-12.01

Load regulation is excellent across the board, with minor fluctuation under full load conditions.

Next we want to try Cross Loading. This basically means loads which are not balanced. If a PC for instance needs 500W on the +12V outputs but something like 30W via the combined 3.3V and +5V outputs then the voltage regulation can fluctuate badly.

Cross Load Testing	+3.3V		+5V		+12V		-12V		+5VSB
	A	V	A	V	A	V	A	V	A	V
1190W	4.0	3.33	3.0	5.01	88.0	12.01	0.2	-12.01	0.50	5.01
240W	19.0	3.32	22.0	5.00	2.5	12.03	0.2	-12.01	0.50	5.01

The SL-1200GW handled our cross load tests without any issues. When hit with 88A, the +12V rail held at 12.01.

We then used an oscilloscope to measure AC ripple and noise present on the DC outputs. We set the oscilloscope time base to check for AC ripple at both high and low ends of the spectrum. ATX12V V2.2 specification for DC output ripple and noise is defined in the ATX 12V power supply design guide.

ATX12V Ver 2.2 Noise/Ripple Tolerance
Output	Ripple (mV p-p)
+3.3V	50
+5V	50
+12V1	120
+12V2	120
-12V	120
+5VSB	50

Obviously when measuring AC noise and ripple on the DC outputs the cleaner (less recorded) means we have a better end result. We measured this AC signal amplitude to see how closely the unit complied with the ATX standard.

AC Ripple (mV p-p)
DC Load	+3.3V	+5V	+12V	5VSB
100W	17	17	25	7
200W	17	20	30	9
400W	23	22	34	11
600W	24	22	33	12
800W	26	21	34	14
1000W	28	22	33	16
1200W	27	23	33	18

Ripple suppression is not bad, it's certainly not the best we have seen in the last year, but it all falls within industry rated tolerances and passed all the tests.

Efficiency (%)
100W	90.9
200W	92.1
400W	93.8
600W	94.4
800W	93.7
1000W	92.7
1200W	91.9

Efficiency is extremely high overall, hitting close to 94.4% at the peak efficiency sector around 50% load. This drops to just over 90% at full load. An excellent set of results for this power supply.

We take the issue of noise very seriously at KitGuru and this is why we have built a special home brew system as a reference point when we test noise levels of various components. Why do this? Well this means we can eliminate secondary noise pollution in the test room and concentrate on components we are testing. It also brings us slightly closer to industry standards, such as DIN 45635.

Today to test the power supply we have taken it into our acoustics room environment and have set our SkyTronic DSL 2 Digital Sound Level Meter (6-130dBa) one meter away from the unit. We have no other fans running so we can effectively measure just the noise from the unit itself.

As this can be a little confusing for people, here are various dBa ratings with real world situations to help describe the various levels.

KitGuru noise guide

10dBA – Normal Breathing/Rustling Leaves
20-25dBA – Whisper
30dBA – High Quality Computer fan
40dBA – A Bubbling Brook, or a Refrigerator
50dBA – Normal Conversation
60dBA – Laughter
70dBA – Vacuum Cleaner or Hairdryer
80dBA – City Traffic or a Garbage Disposal
90dBA – Motorcycle or Lawnmower
100dBA – MP3 Player at maximum output
110dBA – Orchestra
120dBA – Front row rock concert/Jet Engine
130dBA – Threshold of Pain
140dBA – Military Jet takeoff/Gunshot (close range)
160dBA – Instant Perforation of eardrum

Noise (dBA)
100W	<28.0
200W	<28.0
400W	<28.0
600W	32.4
800W	33.5
1000W	35.7
1200W	39.7

This is a quality FDB fan but it is quite aggressive in regards to the fan profile. ASRock have set it up to spin quite fast as loads rise closer to 1000 Watts. It's never that annoying, but it is clearly audible at high loads, even above several system fans. Perhaps not ideal if you want a very quiet high end system.

Temperature (c)
	Intake	Exhaust
100W	35	38
200W	36	40
400W	38	43
650W	43	47
800W	45	53
1000W	47	57
1200W	50	61

Temperatures are well maintained throughout the load range thanks to the high levels of efficiency of the design and the aggressive fan profile.

Pushing the PSU above its rated limits generates an efficiency of around 89.7%. Not a practical situation in the real world of course.

ASRock is a very highly regarded company in the PC sector, and while some of their products have fallen short of the mark, over the years they have earned a good reputation among the enthusiast audience. Right now ASRock have not given me confirmed UK pricing for the SL-1200GW, or anywhere in the world for that matter, which makes it tricky to offer concrete buying advice. I will, however, take a fairly educated guess and assume that the SL-1200GW power supply will be competitively priced when it hits Europe and the United Kingdom.

The SL-1000 GW power supply, for instance, is on sale now for £169.99 in the UK, so I would imagine this higher power 1200 Watt model will be around the £199.99 inc. VAT price point.

First impressions are good. The white matte finish looks clean, and the power supply has some little flourishes around it which indicate that ASRock have put a little time and effort into the design. The modular bay is well laid out, and the cable quality is very good overall. Everything is white as well, which while expected, is not always the case!

Technically, the unit doesn't fail to deliver – load regulation is very tight and the unit is able to deliver continuous high levels of power for even the most demanding of systems. It handled the cross load tests without any issues as well, which is always good to see. The adoption of a quality fluid dynamic bearing fan and high grade 105C rated capacitors from Rubycon and Nippon Chemi Con show that ASRock means business, further exemplified by the 10 year warranty in place.

Fan noise is a little higher than I would have hoped, but the fan profile is set to be rather aggressive, especially when loads get higher. It wasn't annoying (well, for me, anyway) – but if you are susceptible to fan noise and are constantly running with a 900 Watt load, this may be something to consider before dropping your hard-earned cash.

The only real disappointment for me is the somewhat ‘average' ripple suppression. It is not something you would need to be concerned about if you are considering a purchase, but in 2025 I would expect these results to be a little better (lower). Positively, all the protection features worked as they should.

Overall, I would say the ASRock Steel Legend SL-1200GW is a very capable supply which delivers quality power. The overall quality of build, matte white finish, and high grade materials ensure the unit will look good slotted into a white build. We like the adoption of 105C rated Japanese capacitors and the 10 year warranty brings peace of mind to the end user.

Pros:

• 10 year warranty.
• 105C rated Japanese capacitors from Rubycon and Nippon Chemi Con.
• Fully modular.
• Quality matte white finish.
• 150mm long.

Cons:

• Can get a little loud under high load situations.
• Ripple suppression could be better.

KitGuru says: Another great power supply from the ASRock and HEC partnership. High grade materials and quality components inside ensure this unit delivers quality power right up to 1200 watts. It also looks great!

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