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The Worst CPUs Ever Made (2021)

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Re: The Worst CPUs Ever Made (2021)

#71

Post by TheOtherHobbes »

notacoward wrote: post #25
hajile wrote: post #9

This doesn't seem to be the best-researched article out there. If they thought Itanium was bad, they should have looked into the i860. Itanium was an attempt to fix a bunch of the i860 ideas. i860 quickly went from a supercomputer chip to a cheap DSP alternative (where it had at least the hope of hitting more than 10% of its theoretical performance). Intel iAPX 432 was preached as the second coming back in the 80s, b…

At least the 960 was somewhat usable. Many variants were created, and several were widely used in embedded products for quite a few years. The 860, however, was Just Crap. Full stop. End of story. IIRC it had weird double-instruction modes that compilers just couldn't handle, and if you used them anyway (for very necessary performance) then handling exceptions properly was all but impossible. Definitely gets my vote…

Interesting that Intel has such an impressive record of failed designs. Itanium, 860, and iAPX 432 - all anti-classics of their time.

Re: The Worst CPUs Ever Made (2021)

#72

Post by ncmncm »

jeffbee wrote: post #47
als0 wrote: post #16

Earlier quoted context omitted.

The influence of Alpha on modern instruction sets like ARM64 and RISC-V is tremendous. It’s just sad it had to die for this to happen.

How did the Alpha ISA influence RISC-V, other than by its counterexample? Does RISC-V lack an integer divide? "Design of the RISC-V Instruction Set Architecture" mainly uses Alpha in the phrase "Unlike Alpha, ..." i.e. as a warning to future people. In fact, the author fairly well excoriates all of the historic RISC architectures for being myopically designed.

Give RISC-V time, it will be somebody's bad example soon enough.

Re: The Worst CPUs Ever Made (2021)

#73

Post by ncmncm »

jandrese wrote: post #24
masklinn wrote: post #5

The lack of Alpha seems odd, though maybe that should be the worst ISA rather than merely individual CPU?

My impression is that Alpha's ISA was mostly fine except for the power draw, DEC just didn't have the R&D budget to keep up with Intel and all of the foundries and had their lunch eaten by x86 just like every other chip designer in the 80s and 90s.

Alpha was astonishing when it came out. It ran x86 code in emulation faster than any real x86 could go. Its only serious flaw was its chaotic memory bus operation ordering, which came to matter when you had two or more of them. Alpha died because DEC died, not the reverse.

Re: The Worst CPUs Ever Made (2021)

#75

Post by cogman10 »

p_l wrote: post #63
cogman10 wrote: post #48

Earlier quoted context omitted.

> Itanium held the idea that we could accurately predict ILP at compile time (when the halting problem clearly states that we cannot). I don't know where these notions are coming from. Compilers can (and do) reorder instructions to extract as much parallelism as possible. Further, SIMD has forced most compilers down a path of figuring out how to parallelize, at the instruction level, the processing of data. Further,…

The critical difference is that EPIC (the architecture model of Itanium) essentially exposed CPU pipelines naked to the code - so you didn't just have to reorder instructions as optimizers do today, you also had to figure out changes that experience so far suggests is doable either in hw with runtime-only data, or in very tight numerical code. This includes compiler taking the place of branch predictor as well as OOO…

I'm not sure that branch prediction would need to go to the compiler, but definitely agree it'd likely subsume the OOOE scheduling (at very least, it'd be less effective).

That, though, seems like it might make for a good power/performance tradeoff. Those circuits aren't free. We just didn't get to the point where compilers were doing a good job of that OOOE reordering (not until after EPIC died).

The real reason, though, that itanium died (IMO) is most businesses insisted on emulating their x86 code at a 70% performance cost. So costly that it seems like intel/hp spent most of their hardware engineering budget making that portion fast enough.

Re: The Worst CPUs Ever Made (2021)

#76

Post by paulmd »

tsss wrote: post #38
hajile wrote: post #9

This doesn't seem to be the best-researched article out there. If they thought Itanium was bad, they should have looked into the i860. Itanium was an attempt to fix a bunch of the i860 ideas. i860 quickly went from a supercomputer chip to a cheap DSP alternative (where it had at least the hope of hitting more than 10% of its theoretical performance). Intel iAPX 432 was preached as the second coming back in the 80s, b…

Bulldozer gets too much hate IMO. Okay, the instructions per clock cycle were bad and power consumption was high but you can't forget that the FX-6300 was $100 for a >3-core chip that could be overclocked by another 0.7 GHz without issue. The price-performance ratio was better than anything Intel fielded. I'm still running it today.

price-to-performance is the last resort of a company that has failed at taking the performance crown.

Nobody cuts prices more than they have to, but everyone adjusts prices to where they need to go to sell the product. Bulldozer was priced low because it was genuine garbage, it was actually slower than Phenom in a lot of cases (which blows the "it was about price to peformance!" thing out of the water - nobody regresses performance on purpose).

(and before people wind up about the obvious counterexample: Ryzen was priced low because a 1800X was genuinely a lot slower than a 5960X in productivity tasks due to latency and poor AVX performance, and got completely smoked in gaming. If they had tried to go head-to-head with Intel at $1000 pricing they wouldn't have sold anything because it would have been a far inferior package to what Intel offered, they had to cut prices by around half to make it a compelling offering. And even then it was not that appealing compared to, say, a 5820K.)

Companies need to make enough of a showing to attract consumers but if a company prices something super aggressively, there's often a catch. And that's bulldozer in a nutshell. Oh shit the product sucks. What can we charge for a mediocre "8-core" (sorta) that underperforms the 4-core i7? Offer it at i5 pricing and see if anyone bites. If they had managed to achieve good performance, they would have priced it appropriately.

(the other thing is - people prefer to make the comparison about the FX-8350, but that's not Bulldozer, that's Steamroller. Bulldozer was the FX-8150/FX-6350, which actually did outright regress performance vs a Phenom X6, and was priced relatively steeply due to "8 real cores". Bulldozer went up against Sandy Bridge, Steamroller was more of an Ivy Bridge/Haswell competitor, and that's where prices really started to drop. It isn't a huge difference but Intel was making some progress too in those days.)

Price chart: https://www.anandtech.com/show/4955/the-bulldozer-review-amd...

Re: The Worst CPUs Ever Made (2021)

#78

Post by Melatonic »

scrlk wrote: post #51

A different twist on the Itanium: technically bad but ended up as a strategic win for Intel. SGI, Compaq and HP mothballed development of their own CPUs (MIPS/Alpha/PA-RISC) as they all settled on Itanium for future products. After Itanium turned out to be a flop, those companies adopted x86-64 - Intel killed off 3 competing ISAs by shipping a bad product.

Interesting take!

Re: The Worst CPUs Ever Made (2021)

#79

Post by StillBored »

selectodude wrote: post #45
flenserboy wrote: post #34

Earlier quoted context omitted.

Surprising; never knew anyone whose G5s died on them (the systems, sure, but not the CPUs). My dual '04 cpus are still chugging along just fine.

The hotter running G5s had liquid cooling that would inevitably leak and corrode everything.

I'm pretty sure they have a wiskers or wire bonding problem too, and the water blocks clog.

I picked one up that was labeled "crashes while booting" or some such from the goodwill near my house for something like $20 some years back. Brought it home, and noticed that the water block got burning hot when it was turned on, and tubes feeding the radiator were room temp. I broke the water loop open and flushed it out, and a whole bunch of white crap came out of the block. So, whatever the coolant apple shipped with it, was clogging the block. Reassembled the whole thing, had a terrible time getting the air of the system, but in the end it ran pretty good for a while until I left it off for a few months, and it refused to boot. In an act of desperation I hit it with the heat gun and that magically fixed it for a few weeks, and it did the same thing like a year later when I tried to boot it again.

I ran some benchmarks on it to compare with a POWER4 I also have, and yah lots of clock, shitty IPC. It was really cool in 2001, but by the time apple was putting them in mac's they were pretty terrible in comparison to the amd/intel's.

Re: The Worst CPUs Ever Made (2021)

#80

Post by robotnikman »

grp000 wrote: post #55

For a bit of time, I ran an over clocked FX 8320 and crossfire 7970's. The heat that machine put out was tremendous. I only had a wall mounted AC unit so I had to practically take my shirt off when I loaded it up.

Ah yes, AMD/ATI crossfire. I had nearly forgotten that was a thing...
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