I'm trying to upgrade a Gateway DX 4860 which has an Intel I5 3330 for my nephew to use as a gaming PC.
Any advice would be appreciated.
Replace the PSU and drop a GTX 960 or 970 in there. For a prebuilt computer like that (which almost certainly has bad ventilation), the cooler temperatures of the nVidia GeForce cards may be more important than the slightly better performance of the AMD Radeons. I suggest a fully-modular PSU because prebuilt cases tend to have horrible cable management, so a fully-modular one will help alleviate problems. You may also want to cut holes in the side to let it breathe more, if you're okay with jury-rigging.
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I would utilize the whole budget and get a 390x and a better power supply. Sure, the 390x uses more power but that is what the better power supply is for. Great upgrade and will run games much faster than a 960 or a 970. The power supply is a Corsair RM750i which is very reliable and provides 750 watts which should last you a long time. You can use this power supply for your future builds without any problem. Thanks and have a great day!
The DX4860 is based on a H67 chipset and DDR3-1333 RAM,
First off, you need to upgrade the BIOS to a UEFI version, download link:
You can verify that this is the correct upgrade by going to Gateway driver Downoads:
http://us.gateway.com/gw/en/US/content/drivers-downloads and entering "DX4860" as the model no.
You would want to avail the free upgrade to Windows 10 for win 7/8 users before the free upgrade expires on 08/29/2016.. Make sure you have atleast 8GB of DDR3-1333 MHz
This list of upgraded parts compatible with the H67 chipset, ..