Re: [NTLK] [NTLK]Error code 28?

From: Paul Guyot (pguyot_at_kallisys.net)
Date: Sat Apr 13 2002 - 04:09:42 EDT


From: Japecan_at_aol.com
Date: Wed, 10 Apr 2002 11:23:22 EDT

>The error code was on the Newton when I was backing to a flash card! and If
>I remember correctly positive codes are hardware issues like Paul stated.

Error codes are in fact only one part of the error message. An error
message is made of a number and a symbol.
System errors' meaning is usually only contained in the number (which
is negative), symbols are just like categories.
If you have a bus error (such as a priviledge violation), the symbol
tells what this error is (if it's a priviledge violation or something
else) and the value gives you the address.

You can have this in two cases:
a/ a bug that causes a bit of native code trying to read or write
somewhere in memory where it shouldn't.
b/ the fact that the hardware refused to answer

In the case of 28, it is definitely (a). Indeed, at address 28 you
indeed have some hardware (the ROM) but it's not readable in user
mode (this part of the ROM is only used at startup in fact). But
let's say that some bug caused a pointer to be null and the program
tries to access 28th byte from this pointer, it will try to access
address 28 and the system says no.

I even suspect the NewtonOS designers to have made the first page of
ROM inaccessible to help discovering such bugs which are rather
common. (there were some nuts designers at Apple when we come to talk
about NewtonOS RAM's usage, for example the MMU Tables are simply
inaccessible when the MMU is on).

In the case of big random numbers, it could be an hardware error. We
may sometimes find out which address it was, but sometimes we can't
because the address is truncated to the last 29 (or something) bits.

Paul

-- 
Home page: http://www.kallisys.com/
Newton-powered WebServer: http://newton.kallisys.net:8080/

-- Read the List FAQ/Etiquette: http://www.newtontalk.net/faq.html Read the Newton FAQ: http://www.guns-media.com/mirrors/newton/faq/ This is the NewtonTalk mailing list - http://www.newtontalk.net



This archive was generated by hypermail 2.1.2 : Sun May 05 2002 - 14:03:36 EDT