alt Hacker News>Mostly now that there is a lot of software that scales across cores better now
That's pretty much irrelevant since the AMD's FX arch's issues weren't that SW at the time wasn't using all the 8 cores. Intel dropped the Core 2 Duo and Quad into the era where most SW was still stuck in single threaded for a long time and those CPUs still ripped single-threaded SW tasks regardless.
Here's the big reasons why the FX sucked back then and why they still suck today in the multi-thread SW era:
Instead of discrete, fully independent cores, AMD grouped processing units into "Modules" where each module contained two integer execution units, but they had to share critical resources like one FPU, the instruction fetch/decode pipeline, and the L2 cache so when both "cores" inside a module were heavily taxed especially with math or physics-heavy calculations (like in videogames), they choked fighting over shared hardware.
AMD designed Bulldozer with a very long pipeline, betting they could sacrifice efficiency per clock cycle in exchange for extraordinarily high clock speeds(a-la Intel Pentium 4) but the IPC was so bad that an FX core was often slower clock-for-clock than AMD’s previous-generation Phenom II chips and also their power consumption exploded.
FX processors were plagued by high cache latencies and an inefficient memory subsystem as another bottleneck.
Replies
AFAIR Steamroller was a big 'correction' of the Shared resource issues in the arch (I can't remember if other revisions had other improvements).
AMD was also having to deal with the fact GloFo split off and was relying more on general 'bulk' lithography, which kneecapped them for some time especially due to yield issues on the FX series and overall cost of that deal.
Intel also very quickly after, released Sandy Bridge and aggressively scaled it up and down; the 2500K was so cheap yet powerful I know of at least one setup that ran for a decade an only got replaced because they needed to upgrade to windows 11 for compliance-esque reasons. My own 2500K I replaced in 2017-2018-ish, only because either the motherboard took an unfortunate dive and it was easier to replace both at once.
FWIW, I did do a cheapie FX build in 2015ish for my then-girlfriend as a DVR and light gaming/emulation 'under the TV box', and it did the job well for the price, but it definitely wasn't anything amazing.
It was a tough time for AMD for sure. I think the 'split' between the Cat cores (Bobcat/Jaguar) also hurt them from a resource standpoint, although one could argue that it also kept them alive to recover (i.e. Jaguar in XBox One and PS4 being a volume contract part) [0]. They did a lot of moves that caused short term pain (that glofo spinnoff helped pay off the ATI Acquisition AFAIR) but helped them become the company that is still surviving today.
[0] - One odd side note, I still find it odd that they never did a dual channel Jaguar laptop part. I still ask whether it was because it would have made the FX look that bad...
> Instead of discrete, fully independent cores, AMD grouped processing units into "Modules" where each...
Yeah that's hyper-threading intel was doing it as well and all modern CPUs do it as well. Where AMD dropped the ball, was they did not disclose that in their marketing as clearly as they should.
All CPUs today are marketed as x cores 2x threads, back then some AMD marketing genius in their infinite wisdom put 8 cores on the box, instead of the honest 4 cores with hyperthreading.
Hyperthreading/SMT is a significant boon for heavily threaded workloads. What makes that such a win while Bulldozer's implementation of "two integer units sharing a front-end, cache and FPU" is supposedly so bad? Because that description makes the 8 core Bulldozers sound exactly like a 4 core with SMT.
> AMD designed Bulldozer with a very long pipeline, betting they could sacrifice efficiency per clock cycle in exchange for extraordinarily high clock speeds
It blows my mind that AMD watched Intel try to do basically the same thing only a few years prior with NetBurst, and fail so badly that they had to scrap that entire evolutionary branch and start over – and AMD still went and did it again themselves anyway.
>Instead of discrete, fully independent cores, AMD grouped processing units into "Modules" where each module contained two integer execution units, but they had to share critical resources like one FPU, the instruction fetch/decode pipeline, and the L2 cache so when both "cores" inside a module were heavily taxed especially with math or physics-heavy calculations (like in videogames), they choked fighting over shared hardware.
They did just fine in parallel workloads, so I think this is not accurate. The design scaled just fine. The problem was that each core was weak.