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Before the list, the advice that will save most readers of this page a couple of hundred dollars: on an i5-6400 specifically, a used CPU is a better first purchase than a graphics card.
The i5-6400 is a Skylake quad-core with four threads and a 2.7GHz base clock — the slowest of the desktop i5s of its generation, and locked, so there is no overclocking your way out of it. Four threads at that clock is the binding constraint in a great many modern games, and the symptom is stutter and poor 1% lows rather than a low average frame rate. Putting a $300 card in front of it moves the average up and leaves the stutter exactly where it was.
And it sits on LGA1151, which is the good news. An i7-6700 — four cores, eight threads, much higher clocks — drops straight into the same board with no BIOS drama at all, and goes for very little on the used market. That single change does more for how a game feels than any card on this list. Many 100-series boards also received a BIOS update adding Kaby Lake support, which opens up the i7-7700 as well, but check your exact board’s CPU support list before buying one, because not every board got that update and an unsupported chip simply will not post.
Two other things about this platform worth knowing before you spend. H110 boards cap memory at DDR4-2133 and often have modest VRAM-era power delivery, so they are the least happy hosts for a big upgrade. And 100-series chipsets have no Resizable BAR, which means Intel Arc cards are a poor choice here — they depend on it, and the reviews you have read were run on modern boards.
The honest shape of the advice, then: fix the processor, then buy a card in the RTX 3060 to RX 6600 band, and stop. Ten options below, CPUs first.
| # | Product | Price | Where to buy |
|---|---|---|---|
| 1 | Intel Core i7-6700 (Used) | $50–$100 | Amazon · eBay |
| 2 | Intel Core i7-7700 (Used, Board Permitting) | $70–$130 | Amazon · eBay |
| 3 | NVIDIA GeForce RTX 3060 12GB | $180–$280 | Amazon · eBay |
| 4 | AMD Radeon RX 6600 8GB | $130–$190 | Amazon · eBay |
| 5 | NVIDIA GeForce RTX 4060 8GB | $260–$330 | Amazon · eBay |
| 6 | AMD Radeon RX 7600 8GB | $230–$300 | Amazon · eBay |
| 7 | NVIDIA GeForce GTX 1660 Super 6GB | $80–$140 | Amazon · eBay |
| 8 | NVIDIA GeForce RTX 3050 8GB | $180–$240 | Amazon · eBay |
| 9 | A Quality 550-650W Power Supply | $70–$120 | Amazon · eBay |
| 10 | 16GB DDR4 Memory Kit (2×8GB) | $35–$70 | Amazon · eBay |
The picks, in detail
Intel Core i7-6700 (Used)
The upgrade to make before you touch the graphics card. Same LGA1151 socket, same 100-series chipset, no BIOS update needed — it is the same Skylake generation your board already runs. Four cores and eight threads at a much higher clock than the 6400, and it costs a fraction of a modern graphics card on the used market. This is the single best value purchase on this page.
- 4 cores, 8 threads, Skylake
- Drops into any LGA1151 100-series board without a BIOS update
- Substantially higher base and boost clocks than the i5-6400
- Plentiful on the used market
- Doubles the thread count, which is what this platform is short of
- Guaranteed compatible — same generation as the 6400
- Cheap, and it fixes stutter rather than papering over it
- Used only
- Requires removing the cooler and reseating with new thermal paste
- Still four physical cores — it is a reprieve, not a modern CPU
Intel Core i7-7700 (Used, Board Permitting)
The better chip of the two, with higher clocks again, but conditional: it is Kaby Lake, and your 100-series board needs a BIOS update that added Kaby Lake support. Many boards received one and many did not. Look up your exact model’s CPU support list on the manufacturer’s site before ordering — an unsupported chip will not post, and you cannot update the BIOS without a working CPU.
- 4 cores, 8 threads, Kaby Lake
- Higher clocks than the i7-6700
- Requires a board BIOS with Kaby Lake support
- Used market
- The fastest four-core chip this socket will take
- Meaningful gain over the i7-6700
- Still far cheaper than a platform change
- Board support is not universal — verify first, this is the whole risk
- You cannot flash the BIOS without a supported CPU already installed
- Used only
NVIDIA GeForce RTX 3060 12GB
The best all-round card for this platform once the CPU question is settled. It runs a full PCIe x16 interface so it loses nothing on a PCIe 3.0 board, its 12GB of memory outlasts everything else in the machine, and it lands almost exactly where this system stops being able to feed a card. Modest power draw suits an older supply too.
- 12GB GDDR6
- Full PCIe x16 interface
- Around 170W board power
- Single 8-pin connector
- Full x16 — no PCIe 3.0 penalty
- 12GB VRAM is generous at this level
- Well matched to what this platform can feed
- Used market in most regions now
- No frame generation
- Will be CPU-limited in thread-heavy games regardless
AMD Radeon RX 6600 8GB
The value pairing, and arguably the most sensible card for an i5-6400 that is staying an i5-6400. Low power draw so the original power supply is probably fine, cheap on the used market, and entirely capable at 1080p — which is where this CPU belongs anyway. Spending less here and more on the processor is the right allocation.
- 8GB GDDR6
- Around 132W board power
- Single 8-pin connector
- PCIe 4.0 x8 interface
- Excellent 1080p performance for the money
- Low power — unlikely to need a PSU upgrade
- Leaves budget for the CPU, where it belongs
- x8 interface gives up a few percent on PCIe 3.0
- Loses a little without Resizable BAR, which this board lacks
- Weak ray tracing
NVIDIA GeForce RTX 4060 8GB
The efficient new-stock option, and the best choice if the ageing power supply is staying put — it draws well under 120W. Frame generation is a genuine point in its favour on a CPU-limited system, because it inserts frames the processor never had to prepare. The caveat is the x8 interface on a PCIe 3.0 board.
- 8GB GDDR6
- Around 115W board power
- PCIe 4.0 x8 interface
- Frame generation support
- Lowest power draw of the capable cards here
- Frame generation helps specifically with CPU limits
- New with a warranty
- x8 on PCIe 3.0 costs a few percent
- 8GB at this price is tight for the future
- Costs more than a used RTX 3060 with more memory
AMD Radeon RX 7600 8GB
AMD’s current 1080p card, usually a little cheaper than the RTX 4060 and available new. Good performance at the resolution this machine should be running, with the same x8 interface caveat and a modest loss from the absent Resizable BAR. A reasonable new-stock alternative if you would rather not buy used.
- 8GB GDDR6
- Around 165W board power
- PCIe 4.0 x8 interface
- New stock with warranty
- Good 1080p performance, sensibly priced
- New rather than used-market risk
- Comfortably fed at 1080p
- Loses a little without Resizable BAR on this chipset
- x8 interface on PCIe 3.0
- Higher power than the RTX 4060
NVIDIA GeForce GTX 1660 Super 6GB
The cheap fix that still makes a real difference, and a full x16 card so nothing is lost on this board. No ray tracing and no upscaling hardware, but for esports titles and older games at 1080p it is entirely adequate — and at this price you can pair it with the CPU upgrade and still spend less than one modern card.
- 6GB GDDR6
- Full PCIe x16 interface
- Around 125W board power
- Very cheap used
- Cheapest upgrade that changes anything
- Full x16 on this platform
- Leaves plenty of budget for the i7
- 6GB is limiting in newer titles
- No ray tracing or DLSS
- Driver support will end sooner than newer cards
NVIDIA GeForce RTX 3050 8GB
Worth listing as the low-power new-stock option — it runs on very little and some variants need no supplementary power connector at all, which matters if the machine has a small OEM power supply with no spare cables. Performance is modest, but so is the CPU it is sitting behind, and that is the point.
- 8GB GDDR6
- Low power draw; some variants need no extra power connector
- Available new
- Supports DLSS
- Fits OEM systems with weak power supplies
- New with warranty
- 8GB rather than 6GB
- Weakest performer among the current cards here
- Poor value against a used RX 6600
- Several variants with different specifications — check carefully
A Quality 550-650W Power Supply
Check this before ordering a card. Many i5-6400 machines are prebuilt office systems with a 300W supply, a proprietary form factor and no PCIe power cable at all — in which case the graphics card you were planning simply will not fit or run. A modern 550 to 650W unit with the right connectors is the enabling purchase, and it protects everything else.
- 550-650W with 80 Plus certification
- Two PCIe 8-pin connectors
- Modern protection circuitry
- Standard ATX form factor
- Often the thing actually blocking the upgrade
- Protects a machine whose original supply is a decade old
- Cheap relative to the card it powers
- Some prebuilt cases use proprietary supply shapes — measure first
- No performance gain on its own
- Cable management in an OEM case is awkward
16GB DDR4 Memory Kit (2×8GB)
The other cheap upgrade that often matters more than the graphics card on machines of this vintage, because many shipped with 8GB. Modern games routinely want more than that, and swapping in a matched dual-channel kit also fixes the single-stick configuration a lot of prebuilts came with — which costs real performance on integrated memory controllers.
- 2×8GB DDR4 in a matched kit
- DDR4-2133 on H110 boards; higher speeds on B150 and above
- Dual-channel configuration
- Inexpensive
- Fixes the single-stick configuration many prebuilts shipped with
- 8GB to 16GB is a real change in modern titles
- Cheap
- H110 boards cap at DDR4-2133 regardless of what you buy
- No benefit if the machine already has 16GB in dual channel
- Check the board’s supported speeds before paying for faster memory
Buying tips
- Buy a used i7-6700 before you buy a graphics card. Same socket, same generation, no BIOS update needed, and it fixes the stutter a faster card cannot.
- Check your board’s CPU support list before buying an i7-7700. Kaby Lake support came by BIOS update and not every 100-series board received one.
- Avoid Intel Arc on this platform. 100-series chipsets have no Resizable BAR and Arc depends on it.
- Prefer full x16 cards where you can. The RTX 3060 and GTX 1660 Super use the full slot; the RTX 4060, RX 7600 and RX 6600 use eight lanes.
- Check the power supply and its connectors first. Many i5-6400 machines are office prebuilts with no PCIe power cable at all.
- Check whether you have 8GB or 16GB, and whether it is in one stick or two. Both are cheap fixes that are often more useful than a card.
- H110 boards cap memory at DDR4-2133, so do not pay extra for faster kits on one.
- Measure the case before ordering. Full-length cards do not fit many small OEM chassis, and neither do larger power supplies.
As an Amazon Associate and eBay Partner, toptenpick.com earns from qualifying purchases. Prices and availability are subject to change.