Will this PSU Mod work? Radeon HD 7750 in a Dell Optiplex 755 Low Profile Computer?

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SkOrPn

SkOrPn

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Oct 2, 2005
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Ok, peeps, I want to upgrade my little brothers video card here soon as he wants to try more recent games like Crysis 1+2+3, Battlefield 3+4, etc (he currently only plays 2003-2009 games at my request lol). He saw me playing Battlefield 4 the other day and could not believe his eyes and asked me to do the research for him (as I always do). However, his computer which I have done a LOT of work to over the years is aging and is a small Dell Optiplex 755 SFF (Small Form Factor). It has a C2D E8400 3.0Ghz, and I already maxed out the memory to 8gb and he now has a 128gb Samsung 840 Pro SSD (it screams and he loves it). However, his current video card is a Radeon HD 4350 (25 watt) which is lacking in every sense of the word (this used to be my Home Server a few years back) which is for Movies/Netflix Streaming only imo.

Here's the Deal:
I would like to install a Radeon HD 7750 "Low Profile" card (55 watt) mainly because the cooler is very small and the card much more capable than what he has now. Last year, I modded his case with a 120mm intake fan directly next to his 4350 sink so the new card can not have anything bigger on it than what the 4350 has (already big square copper looking sink, and fanless). The sink on this new card looks smaller than what he has now, which is a massive plus. His Optiplex has a manufacturers big white stamp next to the PCI express slot that says "20W Max". With a little research I have discovered that Dell is warning people that that was the maximum power a video card would be allowed (although it can probably go higher). His current PSU and the only one I can have internally is 275w. However, I can mod a secondary PSU (already have it) just for this 7750 video card if necessary.

My question is, if I mod in another PSU just for his new video card will this negate the Dell 20W requirement and draw specifically from the secondary PSU? Also, Looking at this card online at newegg I do not see a power connector. Doesn't this card require an external power supply?

http://www.newegg.com/Product/Product.aspx?Item=N82E16814131509R

I know this card is the most powerful low profile card I can get and runs well under 100 watt maxed which is what I want. With the 1gb of GDDR5 it should allow him to play more recent games with acceptable frame rates I would think. Its a 5 year old machine, so the warranty is no longer an object to worry about. I have been modding computers since the 1980's and this would be easy peasy to do. I just do not know if there will be an obstacle I am not aware of such as too much power being drawn through the mobo regardless of a secondary PSU.

Any ideas would be appreciated. He is poor and can not afford a newer machine, so this is the best he can afford within his means. I think it will work just fine myself, but want opinions none the less. Thanks

SkOrPn

PS. His native resolution is only 1440x900 (16x10) if it matters, which is why I believe this card will run Battlefield 4 just fine for him. Thanks
 
Solution
markwp
No problem. Hope it all works out for you.

As a suggestion, once you install the card, run a quick stress test to be sure the psu will hold. You're right about the odd size, but I believe you can find 350w units out there that will fit and work.

Just so you know, the stock psu has 17a on the 12v rail, so the "real" wattage is only about 204w. Still, if the 7750 only uses 55, you still have 150w to run the rest of the system, and with the minimal configuration you listed, it should be ok.

Mark
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markwp

markwp

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The 7750 is powered from the pci-e slot and needs 55w. It should work in the SFF, IF the psu is at least the 275w variety from Dell. Some of the SFF came with external bricks that were only 220.

The SFF is designed for a 20w max gpu, but dell usually has a pretty good psu. If you have the 275w unit and it's 75% efficient, you have just over 200w available. With the card under load, you would still have 140-150w for the rest of the system which should be enough.

You will definately need the low profile version - be very careful about buying open box - that generally means someone else had a problem with that particular piece of hardware.

Mark
 
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SkOrPn

SkOrPn

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Oh boy, I did not see the "Open Box" logo on that add. Thanks for pointing that out to me Mark.

Yeah it is the 275 watt 80% High Efficiency PSU model, but unfortunately it is a proprietary size/shape/connector so I can not upgrade it without serious soldering modifications... I've done a few PSU mods like that over the years where you simply set another PSU close by and route the needed wires into the machine. However, if this card will run from the PCI-E bus would be a major bonus so I do not have to give him one of my backup PSU's, lol...

I have unplugged his DVD player (he uses an external anyway as to locate it in a better spot in his camper), and his game/movie drive is actually an external 1TB HDD bookshelf type (actually sitting on a bookshelf). So the system really only needs to power the mobo, CPU, memory, single low power SSD and this video card, and not to forget the modded in 120mm fan. Still though I think it will work.

Thanks Mark, I think I will let him know I found a card that just might squeeze a few more years out of this machine for him. By the way, he lives in a very small camper trailer if your wondering why he does not want a larger desktop computer. I hope by 2015 I can find a replacement for him no bigger than a SFF and much more powerful. Well see I guess... Thanks
 
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markwp

markwp

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No problem. Hope it all works out for you.

As a suggestion, once you install the card, run a quick stress test to be sure the psu will hold. You're right about the odd size, but I believe you can find 350w units out there that will fit and work.

Just so you know, the stock psu has 17a on the 12v rail, so the "real" wattage is only about 204w. Still, if the 7750 only uses 55, you still have 150w to run the rest of the system, and with the minimal configuration you listed, it should be ok.

Mark
 
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CarelessGenius

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Hi there SkOrPn,

Did you manage to successfully install a Radeon HD 7750 into the Dell 755 SFF?
Just wondering because I have the exact same desire......and just want to check they're compatible.

Regards,

CG.
 
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SkOrPn

SkOrPn

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Yes, it worked and I did not need the secondary PSU mod thankfully. It took a while but I purchased a SAPPHIRE 100357LP brand new. It has been working flawlessly ever since. However, he has not had the chance to try out more modern games. I think he is stuck in Portal 2 still, lol... Anyway, his storage and optical drive are of the external kind with their own power supplies, so I can not guarantee that you can do this yourself if your still using the internal drives. I also put his machine on a APC Battery Backup to protect from brownouts and surges. Still though with his PSU just barely doing its job it may not take too long for me to have to find another one, lol. IMO, you should always have a PSU that at least doubles the amount of power your system will ever need. I use a 1kW PSU myself and my system only uses 260 watts at any given time, and its an overclocked i7. So, be careful please.
 
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CarelessGenius

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SKOrPn,

Thanks for the reply.
Did you have any problems installing the 7750? I bought a XFX HD6670 (second hand....might have been a dead 'un) and just can't get it to install - the pc can't see the card at all. Maybe a new 7750 would work?

Regards,

CG.
 
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SkOrPn

SkOrPn

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I only had a slight problem with the low profile bracket but nothing to worry about. Your 6670 is only about a 65 watt card so it should have at least powered up. Does this machine work? Does it run with the original card in it? Have you tried the 6670 in another machine? Yes our Dell 755 powered right up and installed drivers from Windows update. I then downloaded the latest version from AMD and installed them. This is on Windows 7 but I plan to try Windows 8.1 for him soon.

Maybe that 6670 is asking for too much from the PSU? Or maybe it's dead?
 
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CarelessGenius

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Yes,
I wondered if it wasn't getting enough power. However, I tried it on another pc with a bigger psu and it didn't work either. so maybe a duff card.

Regards,

CG.
 
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SkOrPn

SkOrPn

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Ah, well there ya go. Time to get a 7750 I think. If you can swing it, it is definitely the best card with the lowest power consumption.

http://gpuboss.com/gpus/Sapphire-Radeon-HD-7750-Low-Profile-vs-Radeon-HD-6670

The 7750 cost more though, but look at it this way, the 7750 will help you not possibly kill your PSU prematurely. The 7750 could be a full 20 watts less for slightly more performance. Well worth the $20 or so higher price tag IMO. Not to mention the extra heat 20 watts will produce inside your case. I found the 7750 at Amazon for only $140

http://www.amazon.com/VisionTek-Products-Express-Graphics-900549/dp/B008RLHFQ6/ref=sr_1_3?ie=UTF8&qid=1390851494&sr=8-3&keywords=radeon+hd+7750+low+profile

OH I forgot to mention, you must get the Low Profile versions of these cards which usually cost more than the standard full sized cards. I wish they would sell Pizza the same way, cheaper the larger it gets, lol....
 
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