[HN Gopher] PowerPC 601 Support Being Retired in Linux 5.10 - Th...
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PowerPC 601 Support Being Retired in Linux 5.10 - The First 32-Bit
PowerPC CPU
Author : rbanffy
Score : 49 points
Date : 2020-10-09 11:18 UTC (1 days ago)
(HTM) web link (www.phoronix.com)
(TXT) w3m dump (www.phoronix.com)
| rwmj wrote:
| I wonder if anyone using Linux regularly ran it on a PPC 601?
|
| Because as a former owner of an Itanium[1] I can say that even
| when a processor is "officially supported" upstream, unless a
| critical mass of people actually use it there are lots of weird
| regressions. Debian/ia64 at the time (2015) only partially worked
| - lots of common utilities would randomly segfault or fail in
| peculiar ways.
|
| [1] https://rwmj.wordpress.com/2014/09/08/raise-the-itanic/
| https://rwmj.wordpress.com/2015/05/03/raise-the-itanic-part-...
| rbanffy wrote:
| How covered by automated tests is the kernel? Some tests would
| require hardware emulators to some degree, but a lot wouldn't.
| cbmuser wrote:
| > Debian/ia64 at the time (2015) only partially worked - lots
| of common utilities would randomly segfault or fail in peculiar
| ways.
|
| It works reasonably well these days, albeit not perfect.
|
| There are issues with kernels >= 4.15 on larger NUMA systems,
| but otherwise it runs mostly fine.
|
| Images can be found here:
|
| > https://cdimage.debian.org/cdimage/ports/
| Scuds wrote:
| The kernel people can say one thing, userland people can say
| another.
|
| "It compiles, it runs! No smoke tests. libc is busted? oh well,
| patches welcome!"
| rbanffy wrote:
| I made the same comment above about the kernel. How covered
| by automated tests is glibc?
| Narishma wrote:
| > unless a critical mass of people actually use it there are
| lots of weird regressions.
|
| Even 32-bit x86 has been having some of those weird regressions
| these past few years.
| gautamcgoel wrote:
| How do these old PowerPC processors relate to the latest POWER10
| processors? Is there a recognizable similarity?
| apaprocki wrote:
| As far as binaries go you can still target the COM instruction
| set with the compiler and the same binary will run on any 32/64
| PPC up to the latest POWER chips.
| rbanffy wrote:
| I was wondering if someone could come up with a POWER9-based
| accelerator board for PPC-based Macs.
|
| Obviously niche, but most amusing. Imagine a 48-core 5 GHz
| MacPro G5.
| Aloha wrote:
| it'd probably totally be.. possible - to get OS X to boot
| on a POWER9 system. There seems to be more interest in
| getting Classic OS to run on modern hardware though
| mhd wrote:
| Mac System 9 running on modern hardware, not in an
| emulator?
| rbanffy wrote:
| I'd totally want my Mac work environment running on a
| dual socket POWER9 workstation.
| Zenst wrote:
| Bit like comparing a 8086 to the latest and greatest, still
| have support for the instructions of the time, but been lots of
| additions since. At least comparing the ISA level.
| fiddlerwoaroof wrote:
| Didn't PowerPC have some unique extensions that distinguishes
| it from the the POWER CPUs?
| wmf wrote:
| Yeah, but Power3 and onward actually implement the PowerPC
| ISA so the differences are smaller than they appear.
| johnklos wrote:
| No. Not even remotely close. The 8086 was an 8 bit processor
| with some 16 bit extensions and segment registers. This is
| worlds different than 32 bit x86. They're worlds apart.
|
| The PowerPC 601 is functionally quite similar to modern 32
| bit PowerPC.
| foobiekr wrote:
| The 8086 was a 16 bit CPU. Every register is 16 bit as is
| the internal and external data bus (the address space is
| actually 20 bits, but that's a different issue).
| johnklos wrote:
| ...except it barely more of a 16 bit processor than a
| Z80, and had 8 bit instructions, extendable to longer,
| like the Z80. Aside from the 20 bit addressing and 16 bit
| offset, the 8088 and Z80 were equivalent.
|
| Or should we call the Z80 a 16 bit processor?
| asveikau wrote:
| It's been more than a decade since I wrote any ppc asm and I
| don't remember much.
|
| I imagine they extended the ISA to 64 bits and maybe that was
| an opportunity for further ISA changes?
| shakna wrote:
| The 601 was pre-standard, so I'd imagine that there would be a
| huge difference.
|
| It had the first implementation of the multiprocessing unit,
| and lacked the load/store and registry units of all the later
| processors.
| Scuds wrote:
| Not knowing anything I'm guessing it's all embedded/non-
| interactive systems, but I can't imagine someone compiling a
| brand new new 5.9 kernel with drivers for a twenty year old
| board.
| protomyth wrote:
| Well, wasn't the 601 a bit different than the 603/604 in
| instruction sets? I seem to remember there were some difference
| from the more refined, later chips.
| mrpippy wrote:
| The 601 had support for some POWER instructions that weren't
| part of the PPC ISA and weren't supported by later chips, I
| know Apple's developer notes for these machines mentioned that
| you had to avoid those.
| Zenst wrote:
| Yes, some of the ISA was still be standardised so wasn't until
| the later chips that got ratified, so some nuances, though at
| hand none I can recall.
| https://en.wikipedia.org/wiki/PowerPC_600#PowerPC_601 covers
| this aspect at least.
|
| Also does seem that 32bit support is on the way out, slowly but
| surely.
|
| Though 32bit will be around for a while in some flavour or
| another, much like IPv4, it just hangs in there working away.
| monocasa wrote:
| > Also does seem that 32bit support is on the way out, slowly
| but surely.
|
| I would be very, very surprised if 32bit support was on it's
| way out any time soon.
|
| E500 cores are basically 603e, and they don't really seem to
| be going anywhere.
|
| Killing off the early non standard core that no one has used
| in decades anymore is one thing, but 32bit PowerPC support in
| general sounds like crazy town to me.
| happycube wrote:
| e500mc is. e500v1 and v2 aren't even user-space compatible
| because Ruiz-era Motorola was cheap and wanted SMD w/o
| Altivec, so they replaced the FPU...
| monocasa wrote:
| They're not user space compatible, but they're very, very
| similar uarchs as you can tell from the supervisor SPRs.
| cbmuser wrote:
| > e500v1 and v2 aren't even user-space compatible because
| Ruiz-era Motorola was cheap and wanted SMD w/o Altivec,
| so they replaced the FPU...
|
| Both run the standard Debian powerpc port with a kernel
| with FPU emulation enabled.
|
| There used to be a powerpcspe in Debian which I
| maintained where even Rust worked after I added target
| support to the Rust compiler (and one very talented
| FreeBSD developer improved the LLVM backend).
|
| However, GCC upstream decided to kill off the powerpcspe
| port for GCC 9, so we had to drop it in Debian.
| jeffbee wrote:
| 32-bit hardware is still widely produced and deployed. Some
| desktop-focused distros have dropped 32-bit x86 support but
| I'm sure the kernel and toolchain will support 32-bit
| platforms for the foreseeable future. Certainly 32-bit ARM
| hasn't gone anywhere, and you can't swing a patch cable
| without hitting a SuperH.
| Teknoman117 wrote:
| You also have the kernel recently adopting both 32 and 64
| bit RISC-V.
| cbmuser wrote:
| > Also does seem that 32bit support is on the way out, slowly
| but surely.
|
| Nah, we're currently even adding LLVM/Rust support for m68k,
| so don't worry, 32-bit support isn't going anywhere soon.
| rbanffy wrote:
| Compiling Rust on a m68k machine would demand some
| patience.
| monocasa wrote:
| I imagine most would be using it as a cross compiler.
| theduncan wrote:
| from the article. "The PowerPC 601 code also
| requires special handling from the rest of the PowerPC 6xx
| support still within the kernel, thus it's a maintenance
| burden."
|
| so yes some differences.
| rangoon626 wrote:
| Incredible that this was being maintained.
| rbanffy wrote:
| PPC ISA is still used in some embedded devices.
| cbmuser wrote:
| We are still actively maintaining support for the Motorola
| 68000 CPU in the kernel which is even older.
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(page generated 2020-10-10 23:00 UTC)