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FPC for DOS / FreeDOS (DOSX)

posted by Rugxulo Homepage, Usono, 16.04.2008, 02:23

> Yes, but only in instruction fetching. IOW the it still couldn't get
> faster than one instruction/clock. The 386 had an even simpler prefetch
386 at best only got 1 instruction per 2 clocks. So, a 386 at the same clock speed as 486 was half as fast (right?).

> my leaving assembler as main programming language, dates from 486 times
> not from Core2 times as insinuated
It's a valuable skill to optimize for size or speed. It's NOT a skill to just say, "Bah, buy a new computer."

> > while Pentium was superscalar (two pipelines),
>
> but very limited. (1 1/2 pipeline, v was very limited).

But "1 1/2" is better than only 1. Trying to compile Allegro on a 486 was painfully slow. ;-) I would easily recommend to 7-ZIP the lib these days instead of subjecting anyone to that. :-P

> > and
> > later models even moreso. The Pentium even had a pipelined FPU. And
> yet,
> > there is plenty you can do to help. At least
> > the Quake authors thought
> so
> > (which used DJGPP for the compiler, BTW).
>
> Actually it is kind of funny that I'm having this discussion. Last
> saturday I junked all old PCs. The slowest PC now is an Athlon XP2000+.

Someone with multiple "old" cpus could always do clusters with things like dynebolic. I might try to convince my bro to try that on all his recycled cpus. ;-)

> I bought not a pentium but a Cyrix (a P166+ for 60% of the
> price of a P133). Due to not having the same fpu/cpu mix tradeoffs, Quake
> was painful.
You can always recompile it these days and try again ;-) (well, if you hadn't junked the computer). Heck, last I tried, Quake wouldn't even run under XP (no surprise there). Of course, DJGPP circa 1996 wasn't quite as compatible as it is now.

But don't worry, even if that doesn't run, there's always Wolf 3D, Doom (or FreeDoom), Chasm: The Rift, Ken's Labyrinth, etc. ;-)

> Of course when I used the difference in money to buy a voodoo card, it was
> maybe still a better deal :)
What OS(es) did you run on that Cyrix machine?

> I do still have several slower computers, but they are not intel/PCs.
Atari 800XL? VIC20? Apple II?

> > I don't understand it fully (who can?), it's very complex.
>
> Using timestamp counters, one can benchmark pretty well. But it
> is hard.

Luckily, even JEMM386 emulates such for us in ring 3. ;-)

> Trick is that not all code is
> important in that respect, and for the code that matters (like the typical
> RTL primitives) it is worth it. See e.g. the fastcode project.
Have you ever heard of liboil? (seems mostly GCC-centric)

> Even then. 10 years * (E100 for upgrade kit every 3-4 years) = E200-300.
> Not trivial, but certainly not infinite.
Sorry if I feel silly upgrading only because it's slightly faster. If an "old" cpu still works and you can be productive on it, why throw it out? Plus, it can be a good learning experience. (link)

> > IMO, they could use tons more help regarding their 586 or less
> > optimizations. However, I'm unlikely to be of use in that regard (at
> > least, not yet). :-/
>
> That's because the people that are still interested in it, are wasting
> their time on writing anything in assembler :-) When they grow over it,
> they pursue other interests. Somehow that is tragic.
GCC is not exactly what I'd call easy to understand (internally). Besides, I have yet to really find any decent 486 optimization tips that truly impressed me (but it's supposedly very sensitive to alignment, way more than 386 or 586). Even VIA's cpus (except upcoming Isaiah) are all in-order execution (no superscalar), and that's why Debian/Ubuntu is only compiled 486+ by default (last I heard). And they use less power too.

> > (I have other computers too, including this P4). They all
> > act differently, but they should mostly run things as
> > fast, if not faster.
>
> They all did, with exception of the upgrade from the C=64 to my first PC,
> a 386. While the 386 had 20 times faster clock, the software was way
> slower, I remember think PC games really sucked, despite the
> PCs larger power (CPU, HD, memory, VGA, SB)

A fast 386 was supposedly able to emulate an Atari800 (1.79 Mhz) at full speed. Supposedly, you need about 10x the power to emulate anything. And BTW, that emulator (PC Xformer) was written (at that time) in assembly for DOS for maximum speed. :-P

BTW, I also heard that the C64 (honestly, I never owned either) did sound mixing in hardware unlike the PC. So that alone would slow it down a bit. Also, PCs were more expensive, so they didn't catch on as well at the time.

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