Re: Tagged memory (was Re: Memory Upgrade)

["Steve Richter" <srichter@xxxxxxxxxxxxx>]

In my view, the best aspect of the ptr tag bit is that pgm errors which
corrupt a pointer signal an exception as soon as the corrupted ptr is used.
On a pc, you might get an exception, or you might just get a reference to an
unintended address.

Now if rochester would only enhance its memory protection by enabling a ptr
to be limited to an address range, a whole class of typical programming
errors could be debugged much easier then they are now.

Steve Richter


----- Original Message -----
From: "Leif Svalgaard" <leif@attglobal.net>
To: <midrange-l@midrange.com>
Sent: Saturday, September 29, 2001 4:40 PM
Subject: Re: Tagged memory (was Re: Memory Upgrade)


> From: Alexei Pytel <pytel@us.ibm.com>
>
> > What about resetting tag bit when any store is made to the pointer area,
> > other than by a pointer instruction?
> > Is it also software ?
> >
>
> eventually everything is done in hardware :-)
> but if the tag bit is reset, you can set it again
> using the SETTAG instruction. Thus the
> hardware reset is superfluous. So again,
> there is NO REAL HARDWARE Enforcement.
>
>
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