From: utzoo!decvax!ucbvax!C70:info-cpm Newsgroups: fa.info-cpm Title: Re: ZDDT is not a simulator Article-I.D.: ucb.1564 Posted: Tue Jul 20 12:35:26 1982 Received: Sun Jul 25 01:45:23 1982 >From rconn@BRL Tue Jul 20 12:35:15 1982 Good point ... I hadn't really used ZDT in moving thru a ROM. If it uses the breakpoint-setting technique of instruction execution, which would include setting one break point after a jump and one at the jump address for a conditional branch unless it was intelligent enough to examine the PSW flags to set only one breakpoint, then it performs no simulation, but it still has to perform some instruction interpretation. Also, are you talking about ZDT or ZDDT? I haven't heard of ZDDT. Finally, the point of the message was to say that these debuggers are definitely NOT emulators. I think the term "emula- tor" is overworked and people have lost track of the meaning ... emulation involves microcode which actually examines and executes instructions for one processor on the architecture of another. Refer to any good text in computer architecture to see my point. For those not familiar with the concept of microcode, we are talking about gate-level (for horizontal microcode) or function- level (for vertical microcode) instructions which are executed within a CPU to interpret and execute the machine language in- structions. Several machines, such as the VAX 11/780 and PDP 11/60, are microprogrammable by the user (some "tricks" have to be used by the VAX user to do this, tho), and the nature of the machine-language instructions recognized and executed by the CPU can be changed. Rick