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Compatibility woes / deprecation (Miscellaneous)

posted by Rugxulo(R) Homepage, Usono, 23.02.2009, 02:24

> > > And why do
> > > you think AMD originally came up with x86_64 and not inteL?
> >
> > I dunno, market pressure? Ingenuity? Boredom? ;-)
> Intel already wanted to use the 64-bit argument as "advantage" for
> Itanium. (as driving force for x86(IA32)->IA64 migration). The last thing
> they needed was anything that detracted from that.

The Pentium had been advertised as having a 64-bit bus (or whatever), not to mention MMX on later models technically being 64-bit. I know that's not the same thing, but that's how it was spun in some cases. (I also have an Atari Jag + CD, which is a hybrid collection of chips, some of which are 64-bit. And it was often called "not 64-bit" by critics because of this despite marketed as the first 64-bit console. "Do the math." Heh.)

> And in general the P4 depended more on "P4 optimized code" than P-III.
> Athlon was even less picky about how the code was optimized.

Well, they broke some common optimizations used in the past due to architectural differences. Of course I think all cpus are like that, even AMDs (from my limited reading of the optimization hints in tech docs).

> > (I don't think Dell ever sold any IA64s to
> > anybody, did they?
> Afaik yes, but Poweredge (and higher) only. Not desktops, and not to
> consumers.

That's what I meant, home use. Of course, even the first 64-bit Opterons were server only, right?

> Core 1 was the last of the Pentium-M's effectively. Used a lot in laptops
> and SFFs.

I remember it, but it didn't get nearly as much push or use as Core 2 has. In fact, GCC 4.3.2 has no core1 optimization (yet??), only "core2" and a bunch of other things ("k8-sse3" must be new, I'll have to try that someday).

> > yet I can't help but feel that all the SIMD crap is (almost) madness.
> It isn't, but it shouldn't be overrated. Rule of thumb, it is useless
> unless you specifically code for it.

I mean, it just feels somewhat useless since it's weird and involves rewriting code manually (although this is a perfect example that "compiler outperforms humans" isn't always true since most compilers can't vectorize worth a damn).

> > AMD really had a good foothold until Core 2 came about. Then all the
> > whiners about Intel's monopoly happily jumped ship due to faster cpus.
> (or they were, like me basically honest, and went with performance/$$$.
> This core2 is the first intel since my i386 SX 20, the rest was AMD or
> Cyrix)

I don't blame them (much, heh), it's just silly to yell and scream about something and then turn around and not care anymore. I guess developers don't want to waste their own precious time.

> I'm not certain about this either, specially if SSE2 can be used instead
> of FPU in all cases (exception, precision)

GCC has "-mfpmath=", which allows 387, sse, or both. But I'm not sure it helps (yet?), highly experimental I think.

> > > a core2 6600 (2.4GHz) outran a 3.4GHz P-D by slightly more
> > > than 100% (which is even more on a per clock basis)
> >
> > 256-bit bandwidth (vs. 128?), I think.
> Where do you get that? One still installs DDR (1,2,3) in pairs for optimal
> performance, and each is 64-bit. So afaik mem bandwidth is still 128bit.
> (unless you use several QPI/HT)

I mean SSE bandwidth (or so I heard).

Anyways, I also read somewhere that Core 2 can (optimally) do four instructions per clock unlike AMD at max. three. That alone is pretty good, so raw clock speed doesn't matter as much as previously (e.g. 486 or 586).

> > > We discourage UPX. I don't see the point.
> >
> > But FPC 2.2.2 includes UPX 3.03 in MAKEDOS.ZIP.
> True, but that doesn't mean you should routinely use it.

Maybe not on Windows for make, bash, gcc, etc, but DOS has no issues.

> > > OTOH, DJGPP seems to live again somewhat after a slump. If DJGPP
> > > really stops, Dos is dead.
> >
> > Well, maybe not. I mean, Turbo C++ 1.01 is "dead" but still used by
> > FreeDOS many many years after-the-fact.
> Is one user left really enough to declare the target non-dead? Is C=64 not
> dead because there are still people working with it? IMHO it is the same
> thing as with cars. At a certain point they are oldtimers, and while still
> cherished, people don't use them every day anymore.

The only reason to not use something old is if the new improves in every way, which is hardly typical.

+ small
+ fast (even can use EMS or XMS for even faster speeds)
+ 16-bit code (which GCC still lacks)
+ supports ANSI C and C++ AT&T 2.0
+ runs on 16-bit cpus
+ all models: tiny through huge
+ nice IDE
+ nice help / function reference

- no sources
- DOS only (no cross compiling supported)
- no newer C++ features (generics, templates, etc.)
- 186/286 optimizations at most (useless for 99% of the world)
- OpenWatcom is better in most ways (but needs 386+ to host)

Besides, there even a DOS extender that works with it (Swallow ... IIRC, untested by me). :-)


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