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List:       bochs-dev
Subject:    Re: Q: hardware breakpoints, "exact breakpoints"
From:       "Kevin P. Lawton" <kevin () bochs ! com>
Date:       1999-10-08 15:50:07
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"Kevin P. Lawton" wrote:
> 
> I've made some good progress with adding hardware breakpoints
> and single stepping to bochs.
> 
> I have yet to read a clear explanation on what "exact
> breakpoints" do (DR7.LE and DR7.GE).  Can anybody offer
> a good explanation, and perhaps exactly which CPU's
> support what with respect to this?
> 
> My take is that with "exact breakpoints" enabled,
> a trap is reported immediately after the instruction
> which had the data breakpoint.  If not, the trap
> may occur further down the road due to pipelining, like
> say delayed one extra instruction.
> 
> My 486 manual says the 486 ignores these bits.  My
> 486DX2 certainly wasn't told this.  When I change the
> LE&GE settings, I get different behaviour.  What's
> up with that?


Oops, I had something messed up with my test program.
Got things working as expected now.

-Kevin


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