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32-bit acorn hardware • The "UnknownVariant" RO2 versions

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For a while now on ArcArc, there's been a ROM200.UnknownVariant ROM file that I haven't seen anybody talk about, presumably because it's very boring.

It boots up with only 6 modules loaded and a seventh (RamFS) dormant:
  • UtilityModule 2.00 (15 Sep 1988)
  • FileSwitch 1.54 (15 Sep 1988)
  • Debugger 1.22 (06 Jul 1988)
  • FileCore 2.00 (15 Sep 1988)
  • ADFS 2.00 (15 Sep 1988)
  • RamFS 2.00 (15 Sep 1988) - dormant, can't be RMReInit'd as it fails with error &108A5, "Too small")
  • Podule 1.08 (09 Sep 1988)
In all likelihood, this was a platform only ever intended to be used for softloading a full RISC OS environment from disc - in this respect it's similar to other similar ROMs that do similar things (such as the RISC OS 2.08 ROM, although that contains many more modules).

So far, so good. However, recently a newer variant of this ROM cropped up (and here's my analysis vs. the final RO2 release for the A500), which Boydie found in an A500 purchased from eBay 20 years ago. The ROM chips were labelled "Final Release RISC OS 2.00". (It is, fairly obviously, not actually the final release - but considering it was intended for softloading, what actually exists there is probably pretty close to what shipped in the final release!)

The internal structure of this ROM set is almost identical to ROM200.UnknownVariant, but it has some differences content-wise:
  • UtilityModule now identifies as 2.00 (12 Oct 1988), and a few other version strings (such as *FX0) were updated with the new date. Apart from this, there are no other changes to any part of this module.
  • FileSwitch was updated to 1.55 (12 Oct 1988), with the only change being that the value of the variable Alias$@RunType_FFF was changed to "Type %0 " instead of "Exec %0 ".
  • FileCore now identifies as 2.01 (15 Sep 1988) and has 2 single-byte code fixes, though I don't know enough to know what they are.
  • ADFS is now 2.01 (25 Oct 1988), has many code changes, and is 16 bytes smaller.
The dormant RamFS module appears to have no changes, and Podule doesn't seem to have any changes either if I'm interpreting things correctly.

Aside from this, there are a few other changes but as far as I can tell, those are the major ones. It seems like the major focus of code development between ROM200.UnknownVariant and this later ROM appears to have been in the the ADFS module, with only minor changes elsewhere.

It would be interesting to see what the boot discs for this softloaded platform looked like, and if there were any particular codenames used for the OS at this point in time - it would help to be able to give these ROMs better names than "UnknownVariant" and "UnknownVariant-2"!

Statistics: Posted by Sophira — Sun Dec 22, 2024 4:13 pm



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