This isn't about making a "lite" distro. Fedora "Core" _should_ continue to ship with the _same_ performance, memory and storage requirements.
I'm talking about not assuming that a 100MHz+ system has a Pentium ISA (instruction set architecture) compatible CPU or higher. Most people seem to assume this, when there are a _lot_ of systems that don't. A _lot_ of 100MHz+ CPUs.
We're talking a "system-on-a-chip" that eats up maybe 1-2Ws, or maybe hundreds of milliwatts. But they run at 133MHz or even higher, have 32-bit or even 64-bit memory bus interfaces, support even 128Mbit SDRAM technology (upto 512MB of SDRAM) and have peripherials up the wazzu on the chip itself (PCI masters, ATA100, PCCard/PCMCIA, USB, etc...).
But the ISA is often only a 486 or lower! Even when the product is sold as 5th-Gen (Pentium) or 6th-Gen (Pentium II) "class" chip!
Now AMD has licensed National Semi's Geode products. The Geode are the Cyrix M2 core, which are Pentium ISA. These are quickly commonplace.
But AMD was is still selling its E86/SCLAN series too (and was its _only_ product for awhile), which kicks some serious butt at 133MHz, with lots of on-board peripherials.
Same deal with STMicro and others. These are _huge_ in Europe, as well as non-US markets, and a lot of imports into the US as well. STMicro is notorious for marketing them as "Pentium/Pentium-II" class because they run at 100MHz, have 64-bit memory busses, PCI, ATA, USB, etc... support. But underneath, the _majority_ of STMicro products are i486 ISA.
These systems are all over the place. In black boxes atop of your TV that have 128MB+ of RAM, 10-20GB disks, etc... Serious power.
That's why I'm all for making the distro i686 optimized, but i386 ISA compatible. With x86-64 being adopting this year, there is little reason to start worrying about "performance." x86-64 distros will be optimized to the max, because x86-64 is a whole new architecture.
But for plain Jane x86, there is little sense to break i386 ISA compatibility. Yes, _assume_ the "performance/memory/disk" equivalent of a Pentium Pro/II or higher. But leave the instruction set compatibility (ISA) at i386 -- please, for Fedora adoption sake.
Bryan J. Smith wrote: <snipping discussion re: relatively fast old-ISA chips>
But the ISA is often only a 486 or lower! Even when the product is sold as 5th-Gen (Pentium) or 6th-Gen (Pentium II) "class" chip!
Now AMD has licensed National Semi's Geode products. The Geode are the Cyrix M2 core, which are Pentium ISA. These are quickly commonplace.
Pentium = 586 obviously.
But AMD was is still selling its E86/SCLAN series too (and was its _only_ product for awhile), which kicks some serious butt at 133MHz, with lots of on-board peripherials.
Also a 586: "The ÉlanSC520 microcontroller combines a 32-bit, low-voltage Am5x86 CPU with a complete set of integrated peripherals..."
(quoted from http://www.amd.com/us-en/ConnectivitySolutions/ProductInformation/0,,50_2330... )
Same deal with STMicro and others. These are _huge_ in Europe, as well as non-US markets, and a lot of imports into the US as well. STMicro is notorious for marketing them as "Pentium/Pentium-II" class because they run at 100MHz, have 64-bit memory busses, PCI, ATA, USB, etc... support. But underneath, the _majority_ of STMicro products are i486 ISA.
Yup, looks like there are a lot of 486s there, looking at this page: http://www.st.com/stonline/products/selector/107.htm
These systems are all over the place. In black boxes atop of your TV that have 128MB+ of RAM, 10-20GB disks, etc... Serious power.
That's why I'm all for making the distro i686 optimized, but i386 ISA compatible.
But... All of the examples you quoted were 486+. Now consider what Jakub Jelinek wrote a little while back: http://www.redhat.com/archives/fedora-devel-list/2004-May/msg00617.html
"I'd like to make NPTL the default threading library for FC3, as a step in phasing out LinuxThreads." ...
"3) NPTL has not been ported to i386, only i486+, x86_64, ia64, ppc32, ppc64, s390, s390x, alpha, sh and sparcv9. i386 (and sparc < v9) lacks atomic instructions powerful enough for NPTL needs. Well, I have tried to port NPTL to i386, http://sources.redhat.com/ml/libc-hacker/2004-05/msg00019.html, but that port is severely limited and maintaining two different IA32 ports would be too much work."
So clearly a very important dividing line seems to lie between 386 and 486 support. I'm all for going wint NPTL as default for Fedora; this is supposed to be a forward-thinking distribution.
But for plain Jane x86, there is little sense to break i386 ISA compatibility. Yes, _assume_ the "performance/memory/disk" equivalent of a Pentium Pro/II or higher. But leave the instruction set compatibility (ISA) at i386 -- please, for Fedora adoption sake.
Well, as far as I can see it sure seems like letting all programs use NPTL-specific features by default can be a somewhat important perfomance win? That's a real difference that ignoring the 386 would give us, and I have yet to see any examples even of modern embedded processors that don't support the 486 ISA (admittedly, I might not have looked hard enough but the examples you came up with were all 486 and you seem to have much more insight in the embedded world than I do). I think that this makes 486 a realistic base target, and given that there isn't much of an NPTL port for 386
I summary, my main point is that 386 is not the same as 486. Jakub suggests in the e-mail I linked to earlier that in general there is little to be gained from going to --march=i486; however, given that there won't be an NPTL library available for 386 I think it feels more honest to just go with --march=i486 anyways. Not that I feel all that strongly about it though.
Basically I think that I'm more or less agreeing with you: Fedora shouldn't dump old ISAs unless there is a real, tangible gain; moving beyond 486 doesn't really seems to give us that. Where we differ is that I think that ignoring the 386 by explicitly using NPTL is a good idea and very much in line with the Fedora goals.
/Per
On Tue, Jun 01, 2004 at 09:37:43PM -0400, Bryan J. Smith wrote:
Now AMD has licensed National Semi's Geode products. The Geode are the Cyrix M2 core, which are Pentium ISA. These are quickly commonplace.
The Geode isnt an M2 core, and its not licensed. AMD bought Geode outright from NS. If you look at the timings the Geode is much more a 486 with extra instructions.
But AMD was is still selling its E86/SCLAN series too (and was its _only_ product for awhile), which kicks some serious butt at 133MHz, with lots of on-board peripherials.
Thats 486 with buggy hw emulation.
support. But underneath, the _majority_ of STMicro products are i486 ISA.
486..
But for plain Jane x86, there is little sense to break i386 ISA compatibility. Yes, _assume_ the "performance/memory/disk" equivalent of a Pentium Pro/II or higher. But leave the instruction set compatibility (ISA) at i386 -- please, for Fedora adoption sake.
Every example you give is 486 or higher ISA, as are the others you missed that I am aware of - SiS55x for example. Going 386->486 makes a really big difference.
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Alan Cox -
Bryan Smith -
Per Bjornsson