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The Worst CPUs Ever Made (2021)

extremetech.com

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Re: The Worst CPUs Ever Made (2021)

#121

Post by unethical_ban »

djmips wrote: post #40
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…

the Cell processor in the PS3 was not terrible in the PS3 and I doubt you ever worked on it. So talk about 'not the best-researched'. You can find many people singing it's praises, including me.

Mod -1: Rude

Re: The Worst CPUs Ever Made (2021)

#122

Post by djmips »

jsjohnst wrote: post #105
djmips wrote: post #40

Earlier quoted context omitted.

the Cell processor in the PS3 was not terrible in the PS3 and I doubt you ever worked on it. So talk about 'not the best-researched'. You can find many people singing it's praises, including me.

> You can find many people singing it's praises, including me. Until today, I’ve never once seen someone “singing it’s praises” that’s actually written code for one. At best, they’d curse it under their breath while saying it had its benefits. Usually however it was a full throated rant about how bad the experience was.

Every single one of them came out a better coder. They might have been dragged kicking and screaming to the multi-core but they would've had to get there in the end.

Re: The Worst CPUs Ever Made (2021)

#123

Post by djmips »

oppositelock wrote: post #102
djmips wrote: post #40

Earlier quoted context omitted.

the Cell processor in the PS3 was not terrible in the PS3 and I doubt you ever worked on it. So talk about 'not the best-researched'. You can find many people singing it's praises, including me.

Haha! I've spent months tuning code to run on the Cell, and I despise that thing. Sony gave you 6 of the 8 SPE cores to use (I think they reserved two, but it's been ages). They are indeed very fast, however, they have no cache coherent access to main RAM and only 256k of memory for each element. So, you have to meticulously write DMA scheduling code to keep them fed. If you're a simpleton like me, you double buffer…

Sounds like you learned a lot and are a better programmer from it. Pretty much everything hasn't changed and you can either hope Moore's law bails you out somehow or you can take what you have learned and apply that to the reality of whatever hardware you happen to be optimizing, CPU or GPU. Sorry it's painful but to eke out max performance it's going to be hard at times.

Re: The Worst CPUs Ever Made (2021)

#124

Post by pinewurst »

chasil wrote: post #103
musicale wrote: post #98

Earlier quoted context omitted.

Personally I can find something to like in most architectures. Cell (for example) was an asymmetric/hybrid multicore CPU; Apple Silicon is perhaps a modern example of asymmetric performance vs. efficiency cores, and also features special-purpose accelerator cores such as the neural engine. The 432 had capability-based addressing. Speed-over-security has had a good run, but with some disastrous consequences. We may be…

Obligatory mention: "RISC instruction sets I have known and disliked." https://www.jwhitham.org//2016/02/risc-instruction-sets-i-ha... https://news.ycombinator.com/item?id=11607119 I might also say that Sun's UltraSPARC was constantly beaten by Fujitsu SuperSPARC. It would have been better to outsource.

SuperSPARC was an earlier TI manufactured part. Fujitsu was (and I think still is) SPARC64, which was a nice series of parts, originally designed by HAL. I used to own a Fujitsu server - fast and built like a brick outhouse.

Re: The Worst CPUs Ever Made (2021)

#125

Post by pinewurst »

sanguy wrote: post #106
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…

i860 did well in embedded applications and for awhile was the mainstay in most RAID controllers and network communication processors. Not what Intel wanted from it but it did have a long life in such applications. I spent many years working on the i860 and i960 and learned to live with its oddities. As for the Cell it was overly complex architecture and had remarkable performance under very optimized code. The hope w…

I think you mean 960 in RAID and comm controllers. The 860 had incredibly bad, almost unbelievably slow context switches. You’d never ever use it in a controller. A dedicated render pipeline is pretty all it was good for, for some value of ‘good’.

Re: The Worst CPUs Ever Made (2021)

#126

Post by djmips »

cbozeman wrote: post #101
djmips wrote: post #40

Earlier quoted context omitted.

the Cell processor in the PS3 was not terrible in the PS3 and I doubt you ever worked on it. So talk about 'not the best-researched'. You can find many people singing it's praises, including me.

That's an enthralling tale, but perhaps you could share why you feel it deserved praise-singing to begin with, and also what titles you worked on, considering many developers were complaining about it when it was current console architecture, and you don't even need to do much of a Google Search to find people bitching about it.

>Google Search to find people bitching about it.

Seriously? You can find people bitching about anything on Google Search. The fact is most people just weren't prepared for multi-core data oriented programming in 2006.

List my titles: no you first

Re: The Worst CPUs Ever Made (2021)

#127

Post by tadfisher »

hilbert42 wrote: post #113

"Note: Plenty of people will bring up the Pentium FDIV bug here, but the reason we didn’t include it is simple: Despite being an enormous marketing failure for Intel and a huge expense, the actual bug was tiny." The fact that the fault was tiny and that few people were affected is definatly NOT the point. The so-called Pentium 'bug' was the result of fundamentally terrible engineering on Intel's part in that the unde…

This is a bit hyperbolic. Intel implemented a known and popular algorithm (SRT [1]) with a standard LUT for the bit patterns expected in IEEE754 FP numbers. They were not the first, last, or only microprocessor design firm to do so. A fault in a script that copied the LUT values to the machines that program the PLAs as part of the manufacturing process led to 5 missing values in the LUT (set to 0), out of 1066 entries.

There's a great writeup with the results of Intel's internal investigation [2], which outlines the challenge in testing production chips for this sort of bug. A key point:

> The fraction of the total input number space that is prone to failure is 1.14 x 10^-10.

So around 1 in 9 billion possible numerator/denominator pairs exhibit the bug. Testing 9 billion double-precision FDIV divides on a 60MHz Pentium would take almost four days, if my math checks out and the CPU could do 2.5 billion divides per 24 hours.

[1]: https://en.wikipedia.org/wiki/Division_algorithm#SRT_divisio...

[2]: https://users.fmi.uni-jena.de/~nez/rechnerarithmetik_5/fdiv_...

Re: The Worst CPUs Ever Made (2021)

#128

Post by Throwawayaerlei »

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…

"We now know that core 2 dropped all kinds of safety features resulting in the Meltdown vulnerabilities."

Curiously, every other out-of-order chip designer except for AMD also designed CPUs with Meltdown flaws. That's per their own documentation ARM, IBM both Power and mainframe, SPARC, and I think MIPS but they weren't entirely clear about it.

Re: The Worst CPUs Ever Made (2021)

#130

Post by ehvatum »

djmips wrote: post #126
cbozeman wrote: post #101

Earlier quoted context omitted.

That's an enthralling tale, but perhaps you could share why you feel it deserved praise-singing to begin with, and also what titles you worked on, considering many developers were complaining about it when it was current console architecture, and you don't even need to do much of a Google Search to find people bitching about it.

>Google Search to find people bitching about it. Seriously? You can find people bitching about anything on Google Search. The fact is most people just weren't prepared for multi-core data oriented programming in 2006. List my titles: no you first

> You can find people bitching about anything on Google Search

And in this thread, you can find credible people with specific complaints about the Cell processor.

> List my titles: no you first

That’s unfortunate. If you’re not full of shit, how could anyone possibly know?

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