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Someone with a more detailed knowledge of RISC OS may correct me, but to the best of my knowledge there _was_ virtual memory protection between applications (th
by zbuf 6y ago
Someone with a more detailed knowledge of RISC OS may correct me, but to the best of my knowledge there _was_ virtual memory protection between applications (the article carefully says "worthwhile memory protection")
Virtual memory was undermined by large portions of the OS being implemented as, effectively kernel modules. That is because this was the provided mechanism for 'shared' libraries; there's no dynamic linker, as such, just syscalls. So perhaps it can be attributed more not to lack of virtual memory, but lack of a mechanism for shared libraries (and IPC)
It is certainly true that as features from multi-user systems began to make an appearance on PC desktops, RISC OS starts to get left behind in this area.
But also recall that wasn't the focus (for a self-selected user base, of course.) An OS geared to productivity, with features like consistent widgets (and style guide), drag and drop between apps, consistent filesystem interaction throughout and standardised anti-aliased font and vector graphic rendering as part of the OS. It's 2020 and it doesn't feel like any of the OSes I use today have anything like the same cohesion (let alone web apps)
They were, however, the early victories of RISC OS. It does look like in the latter years 'easy' stuff was worked on; things like new window decor and textured backgrounds; perhaps diverting attention (either the RISC OS developers, or users) from the core.
I'm rather interested what Acorn's take was on the porting of NetBSD to Acorn hardware (which I first saw at a show in about 1995). With the benefit of hindsight, perhaps RISC OS could have been layered atop of this. A BSD kernel with a RISC OS syscall interface, windowing system and BASIC interpreter to provide compatibility for the wealth of existing software, and a transition to a 'modern' OS. Was this considered at the time? Was anyone at Acorn paying attention to BSD? Was there enough people-power to make it feasible? Was Acorn already in trouble by then? The world could have been a very different place.
- fanf2 6y agoMultitasking in RISC OS was based on swapping the page tables for the application part of the address space starting at 0x8000. Applications were not relocatable, so memory protection was more like a side effect of the address space layout than a deliberate security feature. There was some memory protection to make pages read-only for user code, notably page zero (to trap null pointer dereferences, and to protect the interrupt vectors) but my memory is that the system heap (containing the OS modules) was either directly writable from userspace, or it was trivial to make a system call to get write access.
- laurencerowe 6y ago> Was anyone at Acorn paying attention to BSD? Acorn sold BSD derived RISC iX workstations (the hardware was just rebadged Archimedes) from 1988. https://en.wikipedia.org/wiki/RISC_iX https://en.wikipedia.org/wiki/RISC_iX
- flir 6y agoHad one of those at my VIth Form - think it was an ex-display model Acorn had demo'd at a trade show (suspect it was an A680, it definitely had SCSI). Can't underestimate the lure of that mysterious "real" OS it would boot into. My first exposure to 'nix.
- danellis 6y agoMy first exposure to Unix was RiscBSD, which was netbsd/arm26 running on a RISC PC. Installed from a pile of floppies downloaded at school. Eventually I got an old Elonex 386 that I could install Slackware on, and with a bit of coax I had a 10base2 home network and was being amazed at the concept of running X clients remotely.
- jacquesm 6y agoThey also made a full UNIX workstation called the Unicorn.
- laurencerowe 6y agoHow were the R-series workstations not ‘full UNIX workstations’? Can you post a link to a description of the Unicorn project?
- jacquesm 6y agoThe term 'UNIX workstation' at the time referred to a specific class of machines exemplified by the Apollo and the SUN machines, though, in truth there was all kinds of software running on them. The Torch Unicorn was launched to target that specific market, the idea was to use the 6502 based BBC/Micro as the graphical front-end and then to have a 68K in a separate enclosure running either UNIX System III or a bunch of other OS's. I've seen a demo version of that machine long ago, I don't have any pictures, I didn't think any of this was worth recording at the time, though it was definitely impressive. Please note I used the word 'also', I did not mean to imply the R-series weren't full UNIX workstations, but they came quite a few years after the Unicorn. A later version called the Triple-X ran System V and came with a GUI on the native processor. Edit: found a link with a better description of the Unicorn: http://chrisacorns.computinghistory.org.uk/docs/Torch/Torch_UnicornTechOverview.pdf http://chrisacorns.computinghistory.org.uk/docs/Torch/Torch_... One more with some pics: http://chrisacorns.computinghistory.org.uk/docs/Mags/AU/AU_Sep84_TorchUnicom.pdf http://chrisacorns.computinghistory.org.uk/docs/Mags/AU/AU_S...