7 Best AM3+ CPUs for 2026: The Used FX Upgrade Guide
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You've got a 970, 990X, or 990FX board sitting in a case, it still boots, and replacing it means a new motherboard, new memory, and probably a new power supply. Dropping a faster FX chip into the socket you already own costs a fraction of that. That's the whole appeal, and it's a legitimate one.
Here's the part every older roundup glosses over: AMD stopped making these years ago, so every chip below is bought used or renewed. Listings appear and vanish week to week, which is why each pick links to a live Amazon search rather than a single product page. We checked all seven searches in August 2026 and every one of them had stock from at least one seller.
Quick comparison
| CPU | Cores / Threads | Base / Max boost | TDP | Best for |
|---|---|---|---|---|
| AMD FX-8350 | 8 / 8 | 4.0 / 4.2 GHz | 125 W | The default upgrade |
| AMD FX-8370 | 8 / 8 | 4.0 / 4.3 GHz | 125 W | Buyers who land one with the Wraith cooler |
| AMD FX-9590 | 8 / 8 | 4.7 / 5.0 GHz | 220 W | 990FX boards with liquid cooling |
| AMD FX-8300 | 8 / 8 | 3.3 / 4.2 GHz | 95 W | Eight cores on a modest board |
| AMD FX-6300 | 6 / 6 | 3.5 / 4.1 GHz | 95 W | Cheap, cool-running everyday use |
| AMD FX-4300 | 4 / 4 | 3.8 / 4.0 GHz | 95 W | The lowest-cost working FX chip |
| AMD Phenom II X4 945 | 4 / 4 | 3.0 GHz | 95 / 125 W | Older AM3 boards that won't take FX |
How we picked
Every clock speed and TDP in this guide comes from AMD's own published specifications for these processors, not from a reseller listing — worth saying, because used-CPU sellers routinely copy the wrong figures into their titles.
One number needs care. AMD published two Turbo Core figures for these Piledriver parts: a lower all-core turbo that every core can hold together, and a higher max turbo that only some of them reach at once. The "Max boost" column above is the max-turbo figure for every chip, which is the one AMD's product pages headline. Where the two differ enough to change what you should expect, we give both in the entry — the FX-6300 is the clearest case, at 4.1 GHz max turbo but 3.8 GHz with all six cores loaded.
Beyond the numbers, we weighted three things: whether the chip is actually findable on Amazon today, whether a typical AM3+ board can feed it, and whether it makes sense next to its cheaper siblings.
The Bulldozer generation didn't make the list. The FX-8150 runs a 3.6 GHz base against the FX-8350's 4.0 GHz at the same 125 W, and the FX-4100 manages 3.6 GHz base and 3.8 GHz max turbo where the FX-4300 does 3.8 and 4.0 on the same 95 W — Piledriver simply does more per clock in the same thermal envelope, so the FX-6100 and its Bulldozer siblings are only worth buying if someone is giving one away. We also left out the FX-9370: it carries the FX-9590's 220 W appetite and its board and cooling demands, but tops out at 4.7 GHz instead of 5.0, which makes it the wrong end of a bad bargain.
One honesty note: we have not re-benchmarked these chips in 2026. The rankings rest on verified specifications and a decade of well-documented behavior on the AM3+ platform, so read the performance comments as informed expectations rather than measurements. The pricing language is relative, not absolute, and describes how the listings compared with each other when we looked in August 2026.
1. AMD FX-8350
This is the chip most people should buy, and it's also the easiest to find — the FX-8350 search turned up dozens of listings when we looked, more than any other model here. AMD rates it at 4.0 GHz base and 4.2 GHz max turbo across eight cores, holding 4.1 GHz with every core loaded, with 8 MB of L3 cache and an unlocked multiplier, so there's headroom to push it if your board's power delivery is up to it.
For browsing, office work, media, and older games it should still have plenty in reserve, and eight cores give a mid-range GPU more room before the CPU becomes the limit than the four-core FX parts do. The catch is thermal: 125 W against an AMD-specified maximum case temperature (Tcase, measured at the heat spreader) of 61 °C, and the coolers AMD boxed with these chips were widely reported at the time as loud and working near their limit. Budget for a decent tower cooler.
Price: Mid-range on the used market. Type: 8-core Vishera, 125 W.
Strengths: The best balance of speed, availability, and overclocking headroom on the socket. Weakness: It runs hot enough that a stock cooler is a false economy.
2. AMD FX-8370
Same eight Vishera cores, same 8 MB L3, same 125 W — the FX-8370 is a better-binned FX-8350 with the max turbo lifted from 4.2 to 4.3 GHz. Both chips hold the same 4.1 GHz with all eight cores loaded, so on its own the difference is a rounding error. What makes it interesting is the variant AMD sold with the Wraith cooler, a far larger heatsink than the one in the older FX boxes that reviewers at launch rated much quieter, and used listings for that version do still surface.
Treat the cooler as the product and the CPU as the bonus. If an FX-8370 with Wraith costs about what a bare FX-8350 does, take it. If it costs noticeably more, you're paying a premium for 100 MHz.
Price: Mid-range on the used market, higher for Wraith-bundled units. Type: 8-core Vishera, 125 W.
Strengths: A slightly faster FX-8350, sometimes with a genuinely good cooler in the box. Weakness: The clock advantage over the FX-8350 is too small to justify paying more for the chip alone.
3. AMD FX-9590
Nothing else on socket AM3+ comes close on paper: eight cores at 4.7 GHz base and 5.0 GHz turbo, straight out of the box with no overclocking involved. The 5.0 GHz figure is a max turbo, so under an all-core load it settles nearer the 4.7 GHz base — still higher than any other FX chip manages at stock. Its TDP rating is 220 W, and the maximum case temperature AMD allows is 57 °C — the lowest ceiling of any chip in this guide, on the hottest part. That pairing is the whole problem: the cooler has to move more than twice the heat of a 95 W FX chip while holding the heat spreader 13.5 °C below what the FX-8300 is allowed to reach, so it has far less thermal margin to work with than the wattage alone suggests.
In practice that means a 990FX board with heavy VRM cooling and a liquid cooler, not an air tower and not a mid-range 970. It's also the hardest of these to buy: our search returned a single genuine FX-9590 listing on the first page, with the rest of the results padded out by other FX models. Go in expecting to wait for one.
Price: Premium by AM3+ standards. Type: 8-core Vishera, 220 W.
Strengths: The highest clocks the socket ever shipped, with no tuning required. Weakness: Stock is genuinely scarce, so you may spend weeks watching listings before one appears.
4. AMD FX-8300
The quiet one. You get the full eight Vishera cores and the same 8 MB of L3 as the FX-8350, but AMD rates it at 95 W with a 3.3 GHz base — and, notably, the same 4.2 GHz max turbo. Lightly threaded work should therefore land closer to the FX-8350 than the base clocks suggest; sustained all-core loads are where the gap opens up, since the FX-8300 holds 3.6 GHz across all eight cores against the FX-8350's 4.1 GHz.
That 95 W rating buys real headroom elsewhere. AMD allows it a 70.5 °C case temperature versus 61 °C for the FX-8350, so it's far more forgiving of a modest cooler, and it's a safer match for a 970-class board with lighter power delivery.
Price: Budget on the used market. Type: 8-core Vishera, 95 W.
Strengths: Eight cores and the FX-8350's max turbo without the heat or the board requirements. Weakness: Its low base clock costs it real ground under long all-core workloads.
5. AMD FX-6300
The FX-6300 was the sensible AM3+ buy when these were new, and it has stayed at the cheap end of the used listings. Six cores, 3.5 GHz base and 4.1 GHz max turbo per AMD — 3.8 GHz is the all-core figure, and it's the one you'll see under sustained load — plus 8 MB of L3, the same as the eight-core chips, inside a 95 W envelope. AMD allows it a 70.5 °C case temperature, so a modest cooler goes a long way. It's a Black Edition part, so most boards will let you tune it.
Six cores should be enough for what an AM3+ machine is realistically asked to do in 2026: a browser with too many tabs, a media library, older games. Supply is healthy too; the search brought back plenty of separate sellers. Spend what you save on a GPU, which is the likelier limit in games.
Price: Budget on the used market. Type: 6-core Vishera, 95 W.
Strengths: Six cores and the full 8 MB of L3 in a cool-running 95 W envelope, at the low end of used FX pricing. Weakness: Two fewer cores costs it in anything that scales, like video encoding.
6. AMD FX-4300
Four Piledriver cores at 3.8 GHz base and 4.0 GHz max turbo, 4 MB of L2, 95 W, unlocked multiplier. As a way to get a dead AM3+ board working again for the least money possible, it's hard to argue with, and that 3.8 GHz base is the highest of the 95 W chips here, which should help in lightly threaded work.
Four cores run short quickly once you ask it to do two demanding things at once. This is a chip for a browsing-and-documents machine, a spare workshop PC, or a stopgap while you save for something better — not for a build you expect to game on.
Price: Budget on the used market. Type: 4-core Vishera, 95 W.
Strengths: The cheapest route to a working, tunable FX system with a high base clock. Weakness: Four cores run out of room fast under any real multitasking.
7. AMD Phenom II X4 945
Strictly speaking this isn't an AM3+ chip at all — AMD lists it as socket AM3, 45 nm, four cores at 3.0 GHz, 6 MB of L3, 95 W, with a 125 W revision also sold. It earns a place for one reason: plenty of AM3-era boards will never run an FX chip no matter how many BIOS updates you flash, and the 945 is the cheap, widely stocked quad-core those boards will accept.
It is not the ceiling of the AM3 lineup, and we won't pretend otherwise. AMD's AM3 flagship was the six-core Phenom II X6 1100T Black Edition at 3.3 GHz with a 3.7 GHz Turbo Core, and faster quads went up to the 3.7 GHz X4 980. Either is a better chip if your board's support list covers it, but both are scarcer and pricier used than the 945. The 945 also predates the module design, so its four cores are four full cores rather than two shared pairs — and since AMD didn't sell it as a Black Edition part, the multiplier is locked and tuning means fiddling with the base clock.
Price: Budget on the used market. Type: 4-core K10 "Deneb", socket AM3, 95 W (early revision 125 W — check the OPN in the listing).
Strengths: Cheap, easy to find, and it runs on AM3 boards that refuse FX chips, with no module-sharing quirks. Weakness: Faster AM3 parts exist, and the locked multiplier leaves you no easy way to claw back the difference.
What to check before you buy
Your board's CPU support list, first. Not every AM3+ board takes every FX chip. The 220 W FX-9590 needs a 990FX with serious VRM cooling; the 125 W FX-83xx parts want more than the cheapest 970 offers. Look your exact model up on the manufacturer's site and confirm the BIOS version too.
Cooling, sized to the TDP. The 95 W chips (FX-8300, FX-6300, FX-4300) are fine on a decent air cooler. The 125 W FX-8350 and FX-8370 need a proper tower. The FX-9590 realistically needs liquid.
Memory is DDR3, but the rated speed depends on the chip. AMD specifies a memory controller rated to DDR3-1866 for the FX parts and support for four DIMMs — but not both at once: boards typically only run 1866 with one DIMM per channel, and fall back to DDR3-1600 with all four slots filled. The Phenom II X4 945 belongs to the older AM3 generation, whose memory controller AMD specifies at DDR3-1333. In both cases the motherboard has the final say, so check your board's memory QVL before you buy sticks. If you're reusing your old build, what you already have will fit.
Inspect the photos before ordering. These are pin-grid chips and bent pins are the failure you'll actually encounter. Buy from sellers with a returns policy you have read, and avoid listings that only show a stock photo.
Keep expectations honest. Even the FX-9590 sits well behind a current entry-level CPU in published benchmarks. This is about spending a little to keep a machine you already own useful, not about competing with new hardware.
Frequently asked questions
What is the most powerful AM3+ CPU? The FX-9590: eight cores at 4.7 GHz base, boosting to 5.0 GHz max turbo on lightly threaded loads. It's also the least practical: AMD rates it at 220 W with a 57 °C case-temperature limit, so it needs a high-end 990FX board and liquid cooling. The FX-8350 is the better answer for almost everyone.
Is AM3+ still worth it in 2026? Only if you already own the motherboard. As a cheap way to extend an existing FX machine, it makes sense. Buying an AM3+ board, DDR3, and a used FX chip from scratch does not — a current entry-level CPU beats every processor on this list.
Will an AM3 CPU like the Phenom II work in an AM3+ motherboard? Generally yes, and many AM3 boards will run AM3+ FX chips after a BIOS update. "Generally" is doing work in that sentence, though — check your board's official CPU support list before you spend anything.
Why do these 8-core FX chips feel slower than 8 cores should? Because Vishera pairs cores into modules that share a front end and a floating-point unit. Two cores in a module don't perform like two independent cores under load, which is why an FX-8350 doesn't behave like a modern eight-core part.
Is it safe to buy a used CPU? It's a reasonable risk rather than a free one. Processors have no moving parts, so a chip that arrives working usually keeps working — but silicon does age. Heat, elevated voltage, and electromigration degrade a CPU over time, and a decade-old FX part that spent years overclocked on a heavy voltage bump has had a much harder life than one that ran at stock. That kind of wear typically shows up as instability under load rather than a chip that won't post. The commoner problems are simpler: bent pins from careless removal and damage in transit. Read the seller's actual returns policy before you buy, because not all of them cover bent pins or anything the seller can call buyer damage, and test the chip under load as soon as it arrives, while the return window is still open.
How much RAM do AM3+ CPUs support? They use DDR3. AMD specifies the FX chips at up to DDR3-1866, though most boards only hold that speed with two DIMMs and drop to 1600 with four; the older Phenom II AM3 parts, including the X4 945, are specified at DDR3-1333. Most AM3+ boards accept 32 GB across four slots, but both the capacity ceiling and the speeds that actually run belong to the board, so check its QVL.
Which AM3+ CPU should you choose?
For nearly everyone, it's the FX-8350 — eight cores, clocks a good air cooler can still handle, and by far the deepest supply of used stock. If your board's power delivery is modest or you want a quieter machine, the 95 W FX-8300 gives up base clock but keeps the same 4.2 GHz max turbo, and the six-core FX-6300 costs less again while keeping the full 8 MB of L3. Only chase the FX-9590 if you have a 990FX board, a liquid cooler, and the patience to wait for one to list.
Whatever you land on, pair it with a cooler rated well past its TDP and a good power supply — a decade-old PSU is the likelier failure point in an aging FX rig than the CPU you're replacing.
Tech enthusiast and founder of Technize. Passionate about making technology accessible and helping people make smarter buying decisions.