🚀 go-pugleaf

In article <630@ethz.UUCP> macman@ethz.UUCP (Danny Schwendener) writes:

[a discussion of bus and address errors here]

> While we're on the topic, here's another reason for the Bus Error
> waves: The 68020 allows you to read data on an odd address. The
> 68000 doesn't: a Mac Plus will crash with an Address Error if you
> try to access an odd address (by a dangling pointer, or some
> chaotic program code). The Mac II will probably crash too, sooner
> or later, when the program goes completely nuts and tries to access/
> run/write/execute code on an address that doesn't physically exist.
> Or when it tries to WRITE on an odd address boundary. (reading
> is allowed, writing not. Another mysterious feature of the 68020).

Both reading and writing of non-aligned (odd) addresses is allowed.
However, if you jump to an odd address, you will get a bus error. In
other words, code to be executed must be word-aligned.
--
Darin Adler					       AppleLink: Adler4
UUCP: {sun,voder,nsc,mtxinu,dual}!apple!darin	  CSNET: darin@Apple.com