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The Worst CPUs Ever Made (2021)

extremetech.com

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Re: The Worst CPUs Ever Made (2021)

#101

Post by cbozeman »

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.

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.

Re: The Worst CPUs Ever Made (2021)

#102

Post by oppositelock »

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.

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 your SPE memory, cutting in in half, so 128k to work with, 128k for paging into, and you hope to be done paging before it's needed. Latency to memory is on the order of 2,000 cycles to first byte, but then they arrive fast.

So, what you do is decompose your problem into data streams that can be cruched through, but in such a way that you minimize the need to randomly access much memory. It's often cheaper to recompute things locally than to fetch them from RAM. Random access into your RAM is pointless, so you have to marshal all your input into DMA buffers, do some work, marshal all your output into other DMA buffers, and send back to host CPU.

Anyhow, I got this working. Meshes were being skinned at very high rate, but it was very frustrating. The PPE was really slow, so you had to offload as much as you could to those SPE's. But hey, I may be complaining, but it sure beats dealing with the "Emotion Engine" on the PS2. I can tell you which emotion that engine brings up.

Re: The Worst CPUs Ever Made (2021)

#103

Post by chasil »

musicale wrote: post #98
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…

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.

Re: The Worst CPUs Ever Made (2021)

#104

Post by [deleted] »

TheOtherHobbes wrote: post #71
notacoward wrote: post #25

Earlier quoted context omitted.

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.

[deleted]

Re: The Worst CPUs Ever Made (2021)

#105

Post by jsjohnst »

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.

> 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.

Re: The Worst CPUs Ever Made (2021)

#106

Post by sanguy »

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 was hand tuned libraries would address this; and compiler optimizations would take care of the rest. Neither happened in a meaningful way. We did two major projects with the Cell using it for real-time HDTV compression/direct broadcast applications.

Another one not on the list was the inmos Transputer. Again similar to the Cell; very complex and fast for its time; but not easy to achieve this performance. That was my first job as an EE - we used it on a GPS receiver ISA card in the early days of GPS. It was a good choice as very fast and could keep up with the signal processing that allowed us to roll code updates to add major features as various changes to GPS signals were rolled out (P-code on L2, SA being turned off, and later CA code on L2 being unencrypted). Our competitors had to redesign ASICS to get these new features which means long product cycles and hardware replacement.

Today I find myself doing a lot on the M1 series, as well as Epyc. Now you can give zero shits about clean optimized code and it still runs amazingly fast. Last time I had to do assembler or intrinsics was many many years ago - and I sort of miss that intimacy with the hardware to get the most out of it.

Re: The Worst CPUs Ever Made (2021)

#107

Post by chasil »

pinewurst wrote: post #6
masklinn wrote: post #5

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

Why would Alpha be the worst? I’ve owned 2 of them, 21064 and 21264, and they were fast and reliable.

The only two architectural questions that I know of were...

The weak memory model:

https://devblogs.microsoft.com/oldnewthing/20170817-00/?p=96...

Inability to address low-power designs:

https://en.m.wikipedia.org/wiki/StrongARM

"According to Allen Baum, the StrongARM traces its history to attempts to make a low-power version of the DEC Alpha, which DEC's engineers quickly concluded was not possible."

The other major problem with the Alpha was the high license costs of DEC operating systems, which greatly helped put it in the grave.

Re: The Worst CPUs Ever Made (2021)

#108

Post by kevml »

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…

In the early years, the SPUs were not all functional due to the fabbing process. The ones that had all 8 functional ended up in servers, and the ones with about 6 ended up in PS3s. This still happens all the time with clock speeds, and core counts on modern processors today. I’m sure the fabrication process improved over time, but they disabled the 2 cores to maintain backwards compatibility.

Unrelated: Every time I’m reminded about Cell I’m reminded of the OtherOS fiasco. I purchased a PS3 for the processor solely and I was very upset when I only got a $2 check for it. I never cashed it.

Re: The Worst CPUs Ever Made (2021)

#109

Post by sanguy »

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.

Very true, it was the end of the DEC Alpha as Compaq chose the Itanic.

Re: The Worst CPUs Ever Made (2021)

#110

Post by RachelF »

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…

Yeah, it's good, but the author forgets to mention some other bad chips from before the late 1990's

- The Intel i432 - too far ahead of its time, in Itanium for the 1980's. https://en.wikipedia.org/wiki/Intel_iAPX_432

- The TI CMS320 series of DSPs. So full of silicon bugs it hurt TI badly.

- The Transputer T9000 - very ambitious, but vapourware for so long it killed its parent company. https://en.wikipedia.org/wiki/Transputer#T9000

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