Question RGB, fans, general case cooling advice and PWM help questions


Jun 5, 2008
Posted this on another forum, no responses, so trying here. Yes, it is a long post as I had a variety of questions etc. Onto the questions.

Hi Guys,

So just working out a few things about RGB and fans - I've never bothered with extra fans on any previous system that I've ever built in 20+ years, and RGB is new (my last built system was in 2012).

I have bought the Phanteks Eclipse P500A-DRGB case, which comes with 3x 140mm RGB fans as default. I plan to leave them in the front, as intake.

I have bought 4x SK DRGB PWN 120mm fans in addition to the stock fans. (these are the ones -

My plan was to have a single 120mm at the rear as exhaust, and 3 120mm at the top. 2 of the top fans would be intake and the one furthest back would be exhaust.

As far as I understand, this will create negative pressure inside the case, and should help hot air move out of the case. I should effectively have 3x 140 and 2x 120 fans in front of the CPU/air cooler as intake.

Graphics card is a lowly Radeon 550 2mb - this is not going to be a gaming rig, it's going to be a high end workstation.

I plan to use the stock prism cooler for cooling. I think it should be able to adequately cool the system. My intentions are to use the system for my Astronomy image processing software (PixInsight), which will fully utilise each core, memory and any NVME PCIe disk cache that I set up for processing parallelisation. Given that the cores will be pushed hard, will the stock cooler, and above fan setup be enough? I do not intend to overclock the CPU, or infinity fabric. System RAM will be Corsair LPX 3600mhz (2 x 32GB). RAM will eventually be increased to the system maximum 128GB.

What do you guys think of this plan? I know very little about fans, and I know very little about effective cooling of a case. I have done reading, but obviously lack experience dealing with fan planning, so hopefully my ideas are good and sound.

Now my first potential issue is this is 7 fans. I have the Gigabyte Aorus Master x570 motherboard and as far as I can see, it has 3x system fan headers and 2x system fan/water cooling pump headers. So...2 questions spring to mind so far (I'll work through all my questions logically, in order, so bare with me!).

1. I can use the system fan/water pump combo headers for system fans only if I want.

2. Do I have to use 1 fan per system header? Or, can I daisy chain them? If I can daisy chain them, what are the issues with how many fans per header? Each fan requires voltage to run, and I presume each header has a limited amount of voltage that can run through it. I don't want to overload any particular header.

3. There's no different voltage types for the fans I've chosen - I believe that 12v is the standard?

4. Am I going blind, or is there no sys fan #3 on the motherboard?

I haven't opened up any of the fan packaging yet, I have it safely away in a box until all the parts for the PC build arrive. Will I need to buy additional accessories to enable me to daisy chain etc, or should there be some inbuilt functionality for daisy chaining the fans out of the box?

Next question - I'll be using a AMD 9 Ryzen 3900x CPU. Do I need to use both 12v CPU power headers on the board, or only One? Older systems I have worked on in the past required only a single one.

Another question revolves around RGB. I think I understand addressable vs non-addressable. The former allows the individual LEDS on the LED strip to alternate colours etc independently, whereas the latter doesn't, and the entire strip behaves as programmed.

As far as I understand, addressable headers are 5V and non-addressable are 12V and they are not compatible (as per this page - I believe all of the fans (case included 140mm and the separate 120mm fans are addressable). So, I will need to use a RGB addressable 5v header. The motherboard manual says it has 2 RGB addressable "LED strip" headers - can these be used for the RGB fans that I have purchased?

I'll probably need to split the RGB and daisy chain (which I believe I can do) - 4 RGB on one header and 3 on the other. Is that correct? If so, are there any potential issues with power and potential damage to the RGB fans and/or motherboard from overloading too many of them on a single header? I don't now how much power each individual fan requires for RGB and how that matches to a 5V RGB addressable header.

Looking at the motherboard manual, I see (on p25) LED_C1 and LED_C2 (I think these are non-addressable 12V) and D_LED1 and D_LED2 - I believe these are the addressable 5V headers. Am I correct in my understanding? I think page 29/30 of the motherboard manual confirms this. Just a bit nervous about all of this and seeking external confirmation that I'm not misreading things etc!

Also, if I've understood things correctly and chosen the correct parts, the 120mm fans are PWM. I don't believe the included 3x 140mm fans are PWM (so they should be 3 pin, right)? As far as I can see, all of the fan headers on the motherboard are 4 pin. As I understand, I can connect a non-PWM fan (3 pin) to a 4 pin header, I just need to make sure that I get the plug orientation correct and not to use the 4th (12v pin). Correct?

My last question (for now at least) revolves around the included temperature probes. Should I bother with them? Since they are very long (50cm from memory) and would dangle loose, how on Earth do you use them inside the case without them posing a potential problem to the case internals and dangling about, etc?

Many thanks to anyone who takes the time to assist




We'll work through the items. First, a couple general pieces of info.

RGB Fans are really two devices - a fan, and some lights - mounted in one chassis. They each have two cables. One ends in a female (with holes) standard fan connector with 3 or 4 holes, depending on fan motor type, and it is for power and speed control of the fan motor. The other ends in a wider female connector with 3 holes (looks like it had 4 holes but one plugged up) for power and control of the LED lights in the frame. As you say, your fans have the Addressable RGB (or ARGB, or Digital RGB) type of lights. They differ from the plain RGB light systems in the number of pins on the connector (3 or 4), the voltage supplied to the LED's (5V for ARGB, 12 V for plain RGB), and in the control mechanisms (digital instruction packets for the ARGB system, controlled Ground lines for the plain RGB). Thus they are completely incompitible and cannot be mixed on the same header/controller. In your case, the fan specs indicate that the ARGB fans have daisy-chain cables and connectors for the LIGHTS, but do not say that for their MOTORS.

Fan MOTORS come in two types - older 3-pin fans controlled only by varying the voltage supplied to the fan, and 4-pin newer PWM style that normally receive a fixed 12 VDC power supply and have their speed controlled by the PWM signal they receive on Pin #4. Mixing the types together on the same fan header can be tricky, so it is best to keep the types separated into groups on different headers. The four additional 120 mm fans you bought are 4-pin. Although Phanteks normally sells a 140 mm version of those fans, it appears from the case details that the three they include at the front of the case are 3-pin motor units.

In terms of air flow balance, I prefer to have slightly more intake capacity than exhaust so that the interior of the case has a slight positive pressure. That way any leakage of air through holes is from inside to outside, preventing intake of dusty air. BUT that means you need to include the use of dust filters on the intake fans at the front (very likely included in your case design). Those filters add a "wrinkle" in design plans - they reduce slightly the actual air intake flow to less than the stated fan specs say, so you cannot be sure by calculation of the real balance.

By the numbers, then ....
1. The mobo manual says you can use the SYS_FAN5 and 6 headers for either fans or pumps. You may find in the configuration options in BIOS Setup for those headers that you need to specify which type of device they supply. Why? Many mobo headers for a PUMP will do no speed control - they only supply fixed 12 VDC to the pump because it is designed to operate full speed always. So telling a header it is feeding a FAN allows it to exercise speed control.

Two further notes on configuration of the SYS_FAN headers. You probably will have an option for each for the MODE of control - that is, the method it uses to control fan speed. For 3-pin fans it must be set to Voltage Control Mode (aka DC Mode). For 4-pin fans it should be set to PWM Mode. For each fan header you have a choice of which temperature sensor it should use. You see, these really are automatic systems for TEMPERATURE control. There is a temp sensor inside the CPU chip that feeds out its signal, and the mobo always uses that to control the fan cooling the CPU via the CPU_FAN header. You proably don't even have a choice of a different temp sensor for that header. But for each of the SYS_FAN headers you can choose that sensor or the one on the Motherboard. For the case fans, set each header to the mobo sensor, not the CPU one.

Now to fan count and placement. It is NOT a good idea on the top to set them up with one blowing in the opposite direction from the others. That only creates short-circuit air flows near the top. My suggestion would be to set TWO of your 120 mm fans in the top front, and omit the rearmost top fan. Set up these two and the rear panel fan as exhausts, and connect them together on one header with a Splitter (below). Use another Splitter for the front three fans as intakes. Total six fans. ROUGH air flow balance starting point is, the front fans each have a max intake capacity of 84.5 CFM, but that is reduced a bit by the dust filters in front of them. The top and rear fans each have max capacity 50 CFM. So net is intake capacity exceeds exhaust, but by how much we can't be sure. Alternatively, if you were to install the third top fan also as exhaust, you would have more exhaust than intake capcity, but I am not sure whether overall total airflow would change much to improve your case cooling.

2. Fan headers do their thing by voltage or PWM signal. The limit on the load on each header is in terms of Amps, not voltage. The majority can handle a max load of 1.0 A. Most current fans consume at max 0.1 to 0.3 A, so using 3 (sometimes 4) fans on a single header via a fan SPLITTER is quite all right. Unfortunately, the specs for your fans do NOT specify their max current load, but they are unlikely to use more than 0.3 A each. Fans do not normally come with daisy-chain fittings for the motors, so you will need Splitters. A SPLITTER is a simple device that merely connects all its fans in parallel to the header, so it has two types of "arms". It has one ending in a female connector to plug into a mobo fan male header. Then it has two or three output male connectors for plugging in fans. It has no other type or "arm". You do not need a fan HUB which is a different device. It has those two arm types, plus a single third type of "arm" that must plug into a SATA power output from the PSU to get power for several fans. Do not get a Hub. Splitters will do what you need. One for the front three, one for the top fans, and use a third mobo header for the rear fan. Here's an example of a 2-pack of Splitters with three output arms

and you can get a 4-output set for the same price.

Any fan header can accept coming back to it the speed pulse signal generated by ONE fan. So a Splitter will send back only that signal from ONE of its fans (the one plugged into the only output with all 4 pins) and ignore the rest. You will never "see" the speeds of those other fans, but you don't need them. You CAN use these 4-pin Splitters with 3-pin fans - they simply don't use Pin #4.

3. Yes, all computer case fans are for 12 VDC systems.

4. You are right - there is no SYS_FAN3.

5. Sorry, I cannot answer reliably whether or not you need both CPU power connectors hooked up. If your PSU has both, use them. If not, you can't. To be sure of the answer (to guide PSU selection), check the power ratings of the CPU you plan, maybe ask their Tech support staff.

6. ARGB lights - yes, all you have are this type. Yes, the two D_LED1 (and 2) headers on the mobo are for these. The load limit on each is similar to the way fan headers are limited - max of 5A load per header according to your manual. You won't have to worry about that, though. Your case comes with a built-in ARGB Hub where you plug in ALL the lighting cables from your fans. IF it does not have enough output connectors, you might need to get an ARGB Splitter. For that, contact Phanteks - their systems use non-standard connectors of the lights, so you would need a particular Splitter. The Hub has a cable to plug into a SATA power output from the PSU for all the light power, so it does not load up the mobo header. But there is a cable from the Hub to a mobo D_LEDn header to pick up the mobo's control signals. Using the case's front panel buttons you can manually select lighting patterns and speeds, OR tell it to let the mobo take over that task, and use the Gigabyte RGB Fusion utility to set that up. The Phanteks site does not specify the max load the Hub can handle, but it is likely not less than the 5A limit of a single header. The fan specs show the max current for the LIGHTS in the fans to be 0.35 A per fan, so 6 or 7 or those would not be a problem for the Hub.

7. Fan plugs. Their design ensures they can only plug in one way. When you plug a 3-pin fan female into a 4-pin fan male, it simply does not use Pin #4.

8. Extra temperature probes are mainly for curiosity or very special needs. Actually getting them to read temperatures reliably can be tricky. You do not need them to monitor the general operation of your mobo or your CPU - they already have sensors that work. If you had other temperatures, what use could you make of that info?
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Reactions: dpastern


Jun 5, 2008
Note: in editing for my inevitable typos, I also added another paragraph just before item 2 about fan count and placement.
Many thanks for the reply, really appreciated!!!

The case webpage says it has an integrated dust filter on the front. I haven't taken the case out of its box yet. Going over to a mates place next Sunday to build it together - a fun project for both of us. Gives us an excuse to catch up, and prolly game a bit on the PS4 too and I get to see his new daughter.

The case page also mentions a software free D-RGB controller. I should be able to connect all of the addressable RGB fans to this.

1. I shall go through the motherboard manual again and check the BIOS section for fan/pump selection and DC/PWM modes. I will set the case fans to mobo sensor!

With regards to fan placement, I was thinking to have 3 fans at the top - the front most fan as intake and the 2 at the rear as exhaust - making 3 exhaust fans vs 4 intake fans. Since the top intake fan would be in front of the mobo, I didn't expect it to create any air vortice issues inside the case. Is there any software available that can simulate air flow from fan setups I wonder? If not, it'd be a cool piece of software (non pun intended lol).

2. Amps, of course, what was I thinking? I feel kind of ashamed that I said voltage. I didn't know fan headers typically provide a max of 1a. I might Email Gigabyte's tech support to confirm max amperes for the fan headers. I should Email Phanteks support too to confirm the amperes of the 2 fan types that I'm using. I shall see if I can order a PWM fan splitter from One of my local suppliers and have it arrive during the week sometime.

question - If I have PWM 3 fans connected via a splitter, how is the speed of the 2nd and 3rd fans controlled then? Do they just mirror fan #1? I guess that I should get 2 splitters - One for the front fans and One for the top/rear fans.

3 & 4 - yay, this old dog is learning something new then it seems!

5. I did some more research on this and most people say I only need One PSU cable for the 3900x, unless I am overclocking. They do say however that there is no issue with plugging in both if your PSU has 2. I shall look at the RM850+ manual to see if it has 2 CPU PSU cables or not.

6. I will have to have a closer look at the Phanteks case and the D-RGB hub and see how many connections it offers, etc. So, it seems I can either daisy chain (keeping under the 5a limit for the headers) to the mobo, or go to the case's D-RGB hub/controller. I'll have to look through the mobo manual to see where it mentions the 5a limit. I shall check a local seller to see if they have any Phantek ARGB splitters if the case doesn't come with enough connections. I shall ask Phanteks about the amp limits on the controller.

The splitters may delay my build :(

I'll have to have another look at the Phanteks website to find the current draw on the RGB components on the fans.

I will admit that I have been pretty intimidated by the fans/RGB setups. This has been a great learning experience.

7. Gotcha!

8. I wasn't sure if I'd need the temp probes. I won't bother with them.

Many thanks for taking the time to provide such fantastic answers to my many questions.


Jun 5, 2008
1. Found the fans in the BIOS setup section in the mobo manual. All good.

2. It seems my Corsair 850x PSU has a ATX/EPS 4+4 power cable for the CPU - so 8 pins. It seems the mobo has 2 lots of 8 pin CPU power sockets, so I can't use both with my PSU, just the main One.

3. The Phanteks case has no built in dust filter on the front section - it's the mesh grill only. There is a magnetic dust filter on the top section of the case though.

4. I can't see a DRGB hub mentioned in the accessories. I'll have to take the case out of the box and check this physically to see how it's all set up. A bit confused with this still. The case has controller buttons, but I'm not sure how it's all got to be wired underneath/internally. The Phanteks manual for the case is about as clear as mud lol. I think the best thing is to split the RGB into 2 parts - the 3 front fans to the case and the 3/4 120mm fans to the mobo.

5. I'll see if I can get a splitter for the 3 front fans as it doesn't come with the case. I'll see if I can get a splitter for the separate 120mm fans too. I'll have to research what the appropriate part numbers are and see if they're available locally. Fun, fun, fun! I think this product is called "Phanteks Universal Fan Controller" (referencing this excellent video on the case -

Well, after looking at Phantek's accessories page, I'm still confused!

For RGB, I see these 2 products (splitters):

D-RGB - - only 2 D-RGB connections to the y splitter (3/4 x 120mm fans).

RGB - - same as above, only 2 connections (front 3 x 140mm fans).

I'm probably misunderstanding something and making myself anxious.

For fan control, I see this - But it only goes from 2 to 1 (the link you provided has provision to connect 3 fans). I'm a bit surprised that Phanteks only has this as an option, unless I missed something.

There is a fan hub (the aforementioned "Universal Fan Controller" -, which is rated for a max 48a and has inputs for 3 x 3 pin fan connections, and 4 x 4 pin fan connections plus a universal 3/4 pin fan connector on top of that. If I understand this correctly, it would bypass the mobo controlling the fans. I'd rather use splitters to have 3 fans to each fan header on the mobo and control the fans via the mobo/BIOS. I did find this product (the other 2 suppliers that I've used don't have any 3 to 1 splitters):

What do you think? It only has 1x 4 pin and 2x 3 pin. Given that the 120mm fans are PWM (and thus 4 pin), I'd need like 3 or 4 of these splitters. Or, am I getting confused?

I'm starting to hate fans and RGB lol.

I have Emailed Phanteks about the current draw on both the 140mm case fans and the separate 120mm fans (for both fan control and RGB). Hopefully they get back to me pretty quickly. I have also Emailed Gigabyte about the maximum current on the fan headers and DRGB/RGB headers.

I didn't even think about fans/RGB causing me issues and/or needing accessories to connect it all up. Very frustrating. Worse, I didn't find Phantek's website particularly clear. I guess they built the site on people knowing all about the tech...I'm not a newb when it comes to PC building, but I am a newb when it comes to fans and RGB. They could be a bit clearer imho.

One final thing - do you think the stock wraith prism cooler will do the job - CPU won't be overclocked, only a RX550 GPU (1 slot, doesn't require PCI-E power cable, gets power directly from the slot). Memory will be 3600mhz, so that is technically overclocked, but I can't see that causing much heat. CPU cores will be pushed hard with PixInsight as will the 3 NVME m2 SSDs (used as drive caching).




  1. That front mesh on the case IS the dust filter. From time to time, plan to clean it off.
  2. The ARGB Splitter comes pre-mounted in the case and connected to two control buttons on the top front. Normally that's where you plug in the lighting cables from ALL your fans. From the Hub there will be two cables. One goes to a SATA power output from the PSU for lighting power; the other (may not be pre-attached) CAN go to a mobo ARGB header (see case manual Step 8c). That manual does NOT tell you the detail of how to get the mobo header signal to take over control of the ARGB lights. SOME such systems have a button sequence to make that change, and another related to change back to control by the case buttons. (For an example of a different sequence, see the note about how to turn the lights off completely and back on.) So if you connect all your lights to the Hub, they all can be controlled either way. NOTE that doing it this way is the ONLY way to make ALL seven fan light systems synchronized - that is, do exactly the same thing. IF the built-in Hub does not have enough outputs (the Digital RGB Hub the sell separately has three outputs), you can get from Phanteks their 3-pin Digital LED Extension Y-Splitter Cable

to convert one output into two. (You also linked to this on the Phanteks website.) To make seven from three, though, you will need four such Splitters - you plug the fourth one into one of the two outputs of one of the others to make one small "stack". As far as load goes, the fans have specs of 0.35 A max per fan for lights, so 7 of them is 2.5A, and the separate Hub they sell says it can supply up to 7 A total from all output combined, so no problem at all.

Note that, because Phanteks uses a "non-standard" ARGB connector, to connect any of these to a mobo header directly requires an adapter, similar to this that has two outputs from one mobo header,aps,179&sr=8-2

(Note that the second item you linked to on the Phanteks website is NOT this one - the one in your link is an adapter to connect the FOUR-pin plain RGB header to a FOUR-pin plain RGB light system.)

5. The three front fans pre-installed have 3-pin motors and must be supplied from a header using DC Mode. I suggest you connect all three to the SYS_FAN2 or 4 header on the front middle edge of the mobo using a Splitter similar to the one I linked before. And remember I said you can get a pair of those as 4-output ones? Well, do that and use the other to connect all three top fans plus the rear fan to the SYS_FAN1 header at top rear of the mobo. Configure that one to use PWM Mode since that group is all 4-pin motors. Whether a fan is used for intake or exhaust does not change how its speed is controlled, so this is a simple way to connect all those fans' motors. Those two Splitters are less costly than a Phanteks Universal Fan Hub.

Oh, 4-output fan Splitters are not really common. But you can make your own easily with the very common 2-output kind. Buy three Splitters with 2 outputs each, and plug two of them into the outputs of the third. That "stack" makes 4 outputs from one header. If you use only two Splitters, one into one output of the other, you get three outputs. Doing this does not have any impact on electrical load - the load is determined solely by the motors.

The number of pins in a Splitter output can cause confusion. Any mobo fan header can only deal with the pulse train speed signal of ONE fan sent back to it, and that signal is always on Pin #3. So any Splitter will have all 4 pins in only ONE of its outputs, and skip Pin #3 in the others to eliminate those speed signals. But Pin #4 that carries the PWM signal is always there.

I've said in many posts, fans actually are controlled by the mobo to achieve a TEMPERATURE target at a relevant sensor. The mobo really does not care what the fan speed is, and does NOT use that info to do its job. It simply alters the fan speed to whatever it takes to achieve that temp target by air flow to remove heat. It really is NOT "speed control". But the speed in interesting to users, so it is displayed for you. And it's easy, because the speed signal IS used by the mobo header for a different function - detecting fan FAILURE. If it gets no fan speed, it will alarm you so you know to investigate and fix. BUT when you use a Splitter or a Hub for fan motors, and not all of the speeds are returned, the mobo cannot monitor ALL of them for failure. So YOU need to check from time to time that all the fans still are running.

I note you've made a slight change in fan layout plans, so that at the top only the front one of that trio is mounted as an intake fan. That will help achieve better balance.

For a CPU that is not overclocked and overdriven, I expect the stock cooler will do the job. BUT I do NOT really know about that for sure. Maybe start another thread aksing specifically that question to keep that thread simple.
Reactions: dpastern
Nov 10, 2020
Paperdoc -

Thank you for your detailed explanations - it is really invaluable to someone building a system with ARGB for the first time. My last build was 2012 and I just purchased this same case for a new build, so finding this thread has been a huge time saver for me.

Thanks again -
Reactions: dpastern