Path: utzoo!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!aplcen!samsung!cs.utexas.edu!sun-barr!newstop!east!hinode!geoff
From: geoff@hinode.East.Sun.COM (Geoff Arnold @ Sun BOS - R.H. coast near the top)
Newsgroups: comp.sys.ibm.pc
Subject: Re: NuMega's Soft ICE questions
Keywords: Softice, NuMega
Message-ID: <1537@east.East.Sun.COM>
Date: 9 Feb 90 13:28:45 GMT
References: <2078@tellab5.TELLABS.COM>
Sender: news@east.East.Sun.COM
Reply-To: geoff@East.Sun.COM (Geoff Arnold @ Sun BOS - R.H. coast near the top)
Organization: Sun Microsystems PC-NFS Engineering
Lines: 45

Quoth fayne@tellab5.TELLABS.COM (Jeffrey Fayne) (in <2078@tellab5.TELLABS.COM>):
#I seriously considering purchasing NuMega's 386 debugger, however
#I have a few questions for anyone who has used this program:
#
#	1) Is it as powerful as the ads make it out to be ?
#	   I'm particularly interested in it's 'back trace'
#	   capability (will it allow you to step backwards
#           thru your code once a breakpoint is hit or will
#	   it just show you how you got to the breakpoint?).

I've been developing PC-NFS since 1985, and over that time I've
come to rely on three debugging tools: The Network General
Sniffer, IBM's PC-Watch, and SoftIce. Each is, in its own way, invaluable.

The back trace facility stores every instruction within the trace range
in the circular buffer. Whenever SoftIce gets control (via breakpoint,
exception, or hot-key) you can browse this buffer. Most of the work I
do is low-level assembler stuff (redirector, network driver, etc.), and
the most painful bugs are always blown stacks, segregs, etc. which
usually result in a return to a random address. Since Intel (in their
infinite wisdom) failed to make 00H the "halt" instruction (didn't we
learn ANYTHING in the 60s?), the back trace is the best way of nailing
things. It even works across reboots, so that I can trace through all
the DOS and driver startup code.

#[Questiona about TurboDebugger and PLINK)

No data. I use Microsoft Link, don't use overlays.

#	4) Ideally, I would eventually like to run SoftIce under
#	   VM/386 (multitasker), is this possible? If not why not
#	   and will it run under any other multitasker?

Almost certainly not. SoftIce takes over the 386 and runs your DOS
session in a virtual 8086, which will conflict with any other software
which wants to act as a hypervisor. For example, you can't run
Windows/386 with SoftIce. (As far as I know, no microprocessor has the
necessary hooks to run a fully recursive VM architecture - i.e.
running a 386 virtual machine under a hypervisor. In this respect we
still can't emulate VM/370. One day, maybe.)

Geoff Arnold, PC-NFS architect, Sun Microsystems. (geoff@East.Sun.COM)
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