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Old 09-30-2018, 01:13 PM   #21
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Default Re: Your Video Card Cooling Mods - Sapphire Radeon HD4650 1G

well, i'd just like to affirm that your testing methodology is sound on both the 2400 xt and 4650.

with the ambient temp of 29C and the max load temp of 37C, u have a delta or rise above ambient of 37-29=8C. since the 2400 xt has a tdp of 20w and the 4650 having a tdp of around 50w, the heatsink has to handle 2.5x the heat output of the 2400 xt. since the heatsink gave a +8C delta above ambient with a 20w tdp heat load, so with 2.5x higher tdp to handle, we have 8x2.5=20C delta above ambient. with an ambient temp of 29C, so we should be expecting temps of around 29+20=49C on the 4650. in practice, your result was a max load temp of 50C.

so i just love it when theory matches up with practice! this means there are no mounting issues with the heatsink and it works perfectly exactly as it should! the above theoretical calculations and momaka's practical testing methodology above should be useful for anyone looking to measure the tdp of a heatsink and how much heat it can handle and what temps u should be expecting. therefore, this negates any newbie mistakes of using an inappropriate heatsink for a video card and ending up with an even worse overheating video card!

let me tell u all about it. recently, i bought a few video cards off junkbay that came with third party heatsinks. thing is, they all had inappropriate heatsinks for the tdp required. i had a 5870 with arctic twin turbo pro. arctic lists the max tdp handling capacity of the twin turbo pro as 125w and the 5870 has a tdp of around 200w! the video card turned out faulty when i tested it and i had to file for a refund.

then i got another 5870, this one has a zalman vf1000. i put a zalman vf1000 on my 6800 ultra before and it struggled to contain the 75w tdp of the 6800 ultra. i dont need to tell u what happens when u try a 200w heat load on a heatsink that can barely handle 75w! i also found that the plastic washers on the back of the card to insulate the pcb from shorting on the spring loaded screws had melted and fused onto the card's pcb. i wonder how hot the gpu ran to cause the plastic washers to melt like that. over 100C?

then i got an asus 4870 dark knight. the dark knight cooler has 4 heatpipes and its design is almost exactly like the vf1000 except upside down, so its an inverted vf1000. the 4870 has a tdp of 150w. no way that dark knight cooler can handle that when the similarly performing vf1000 struggled with 75w tdp.

i find it mind boggling when ppl try to supposedly "improve" the cooling of their video cards but have no idea what they are doing and make the cooling worse instead than even with the stock cooler! so i hope some grey matter use with mathematics and practical physics above, teaches ppl to use the right cooler for your video card!
Originally Posted by momaka View Post
I was getting over 65C on the core (under full load). notice the darkening of the PCB on the back side under the GPU chip? this card came out of a very dusty OEM PC
the 65C u got isnt hot enough to cause the pcb to darken. rather its the most likely cramped oem casing and poorly ventilated oem pc case plus the combined effect of the dust that led to the gpu running even hotter than the 65C u got. i estimate the internal case temps of the gpu running at max load hit over 80C maybe even close to 90C over a prolonged period. thats what caused the pcb to darken.

i highly doubt that gpu will last long. it might need a reflow soon. tho with the 50C load temps now with the new heatsink, the gpu will be lovin' u for givin' it a chill from all the stuffiness it experienced with its previous owner!
Originally Posted by momaka View Post
I also had some Shin-Etsu thermal compound that I wasnt sure if it was good or not, as it looked rather hard to spread (thick, but not dry).
i have used shin etsu before and i have both the x23 7783d and g751 pastes and yes they are thick and i had to spread them with a spatula. the reason for that is that it has to be thick enough to iron out all the microscopic air bubbles to improve the heat conductivity or sumthing since air is an insulator, not a conductor of heat. i could be wrong tho on why it has to be thick to be good, so dont quote me on that.

i practice my tim application technique by practicing spreading cold butter on bread with a metal butter knife. kills two birds with one stone... or in this case, feeds two mouths with one toast.
Originally Posted by momaka View Post
Ive played around with these small coolers quite a bit, I can tell you from experience that they are not capable of more than 30 Watts TDP max.
well dont toss em just yet. they should do well for cooling the entry level series of each generation from the 2000 to 5000 series all of which have 20-25w tdp. e.g. 2400 pro/xt, 3450/3470, 4350 and 5450. all of em should have 43mm square mounting hole pattern which fit the cooler. in fact, that 4650 stock cooler should work nice in replacing the stock passive heatsink of my 5450. u should sell that 4650 stock cooler to me! lol!

also, if u dont mind and have the time, u should try that 4650 stock cooler on the dell 2400 xt instead. i wonder how it would perform. i theorise it should perform great! not sure what the ambient temp was when u tested the 4650 stock cooler and got that 65C load temp result but i am going to ass-u-me the ambient temp is 29C. therefore, 65-29=36C delta above ambient. since the 2400 xt has 2.5x lower tdp than the 4650, 362.5=14.4C delta above ambient. with an ambient temp of 29C again, we get 14.4+29=43.4C. so u should get around 43C load temps give or take a couple of degrees with that 4650 stock cooler on your dell 2400 xt. well, if u have some spare time, that would be an interesting experiment to try out! give it a go and lemme see the results! thanks! hehehe...
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