xerox 19770813 D0 Simulator Status free download

File name 19770813_D0_Simulator_Status.pdf

XEROX SYSTEM DEVELOPMENT DIVISION Communications Systems August 13, 1977 To: Metcalfe XEEex SDD ARCHIVES I have read and understood From: Crowther Pages _________ To _________ Subject: DO Simulator status. Reviewer Date_ _ __ '* of Pages _ _ _ Ref.:-t1<::'OD - :'03 The DO simulator and its associated ddt now exist as mesa programs on (Crowther) dzeroSi mulator.i mage. The simulator has been tested on two sections of microcode provided by Don Charnley - the first is a routine to do unsigned multiply, and the second a fragment of the emulator. The latter was successfully run on a tiny mesa program which fitted in a single quadword. The mesa program computed a series of triangular numbers, exercising both main memory access and the hardware stack features. The DO mechanism for accessing more than a single quadword is yet to be specified. At the present time there is no microcode assembler for the DO. Thus the load and dump commands probably don't work (although the load will load the output of a dump), and extensive testing of the simulator is awful work. (It took hours to get Charnley's programs correctly assembled.) In these circumstances one must expect a rash of minor bugs still to be found. The ddt is a crude version of standard PDP-I0 ddt. It is meant to be self documenting, but probably succeeds only for people with some experience with other ddt's, or those who have at least read the DEC ddt manual. The simulator tries to mimic the actual DO design at the hardware register level, and is thus at least partially documented by the DO manual itself. The help commands for the ddt provide further information about the simulator and its control. The simulator and the ddt are really two quite separate entities. The only communication between the two is a pair of routines called ReadSimulator and WriteSimulator, which deal with a 32 bit address and a 32 bit contents, plus a number of signals which come up from the simulator when the user tries to do illegal or non-implemented things. The simulator has a register for each DO hardware register (more or less), and keeps two copies of each register, one for the start of a 70 ns simulated cycle and one for the output of that cycle. At each simulated clock tick the start registers are loaded from the output registers of the preceding cycle. Unlike the registers. there .is no attempt to simulate the DO gates. Whenever a gating function is required the simulator computes it in the most convenient fashion. All of the simulated hardware registers plus many of the gating functions are accessible to the ddt