[Oberon] A2 Repository

Michael Schierl schierlm at gmx.de
Sat Jun 29 22:10:20 CEST 2019


Am 20.06.2019 um 23:25 schrieb Michael Schierl:
> When taking r7367 and using Heaps.Mod from r7366 (plus adding an empty
> CheckAssignment* implementation), the system boots again. So, the triple
> fault is likely caused by a change in Heaps.Mod.

After some more investigation, it is only indirectly the case.

The culprit is the variable "cardSet" introduced here:

As a consequence, the size of the linked images increases by 128KB, and
since the default OBL.Bin loader tries to load the linked image into
conventional memory (640K ought to be enough for anybody), the image
just got too large.

> For r7409/r7412/r7461 there were many compile time errors I was not
> quickly able to fix.

Reason here was the change in
that changed the namespaces to be separated by dashes instead of dots. I
am unsure why this broke the Bios32 build but not the WinAOS build, but
since this got fixed some revisions later, probably it is not important

Anyway, when reverting this change (and also reverting the change how
GetModuleSegmentedName is built), these versions compile and run again, too.

Coming back to our main goal of recompiling a recent A2 version: The
linked image of recent versions is a bit over 800KB, so I assume it is
unrealistic to get this stripped (without breaking the system) to fit
within 640KB. There seems to be a second Boot loader (OBLUnreal.Bin)
available, which supposedly tries to avoid this limitation by switching
to "Unreal mode" (also known as flat memory segment hack) and loading
the image into extended memory instead.

However, I was not able to make this bootloader boot (on VirtualBox, at
least), neither when using a current version of A2 nor when using an old
version that still boots fine with OBL.Bin.

So I guess, to wrap this up, the issue with recent A2 native builds is
that the linked image got too large for being loaded with OBL.Bin, and
the alternative OBLUnreal.Bin does not work (on all hardware where
OBL.Bin worked). Probably one could spend a lot of time finding the
latest version that can get stripped down to fit into conventional
memory, but I don't see a point in doing that myself.

Other solutions could be to either implement a self-decompressing image
(so it can be loaded with original OBL.bin; but even that might be "not
enough" at some point) or add support for creating Multiboot or
Multiboot2 images (and load them with a Multiboot-supporting bootloader,
like SYSLINUX, ISOLINUX, PXELINUX or GRUB; disadvantage being that it is
no longer possible to install A2 to an empty hard disk just from within
A2). But both of them are a lot more work than I'd like to spend on this

So I will stop my A2 endeavors here - since I also noticed that
OberonGadgets apparently disappeared from later A2 versions, I'd
probably stick with earlier versions anyway :D



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