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Re: I have a IIgs. So now what?
David Empson wrote:
> Tristan Mumford <xtristan.xmumford@xgmail.xcom> wrote:
>
>> I'll have to dig the computer out of the shed one day. It's in a special
>> padded carrybag with spaces for the keyboard and mouse. I seem to recall
>> that it may also have the OS built into ROM.
>
> That's basically true for all Mac models prior to the iMac.
>
> The ROM contains a large chunk of the system software, including most of
> the OS, file system and GUI code.
>
> It won't work on its own, however - you need a bootable system floppy
> (or hard drive) to do anything useful. The system software on the boot
> disk includes some parts which are missing from the ROM, and patches to
> various parts of the ROM code.
It actually has the basic runnable OS in ROM. A special key combination on
startup is needed to get it though. Otherwise it looks at the boot device.
I'm guessing it dumps it into RAM or something. I actually found out about
the ROM OS off the internet. Apparently it was only in some of them. Mine
had it.
>
> This is the same principle on which the IIgs toolbox firmware was based
> - the ROM contains a basic suite of toolsets, but none of the file
> system or OS code, just enough to bootstrap load a single sector from a
> floppy or hard drive, from which the OS gets loaded. When you boot into
> ProDOS-16 or GS/OS, toolbox patches and additional toolsets are loaded
> from disk, replacing some parts of the ROM-based toolbox.
>
> Application code generally doesn't need to know where a particular
> toolset or function came from - it can be in RAM or ROM without
> affecting anything other than performance (and memory usage).
>
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