Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!utgpu!water!watnot!watmath!clyde!rutgers!cbmvax!daveh From: daveh@cbmvax.UUCP Newsgroups: comp.sys.amiga Subject: Re: Some thoughts and questions about the Ranger Message-ID: <1518@cbmvax.cbmvax.cbm.UUCP> Date: Mon, 9-Mar-87 14:29:59 EST Article-I.D.: cbmvax.1518 Posted: Mon Mar 9 14:29:59 1987 Date-Received: Tue, 10-Mar-87 05:44:41 EST References: <2725@well.UUCP> Organization: Commodore Technology, West Chester, PA Lines: 77 in article <2725@well.UUCP>, ewhac@well.UUCP (Leo 'Bols Ewhac' Schwab) says: >>>I imagine (with maybe a bit of clever programming) the Amiga could >>>emulate a C64 in full time (including to the smallest details including >>>sound, sprites, the different video modes, etc), in software only. >> >>It might be possible, however it is often a mistake to assume that the >>predecessor is so that you can emulate it in software >>in real time. The 6502 is still a fast microprocessor, > > Really? You think so? The fastest I've ever seen those things > commercially is 2 MHz. The C-64 runs at (slightly less than) 1 MHz. After > moving to the 68K, the very THOUGHT of going back to the 6502 makes me gag. Well, when you consider that the 6502 running at 2MHz is accessing memory at the same rate as an 8MHz 68000, (both have memory cycle times of 2MHz), it doesn't make the 6502 sound all that slow. Of course, the 68000 is accessing 16 bits of memory in most cases, versus 8 bits, it has much more internal efficiency, etc. Still, I don't think you'll have all that much trouble emulating the C64's 6510, which, by the way, runs at 1.02MHz in the NTSC version of the C64 (the C128 can run at 2.04MHz). >>especially when >>munching 8-bit data, and the VIC chip is a pretty tricky little gadget >>by itself. >> > It's tricky because of all the design barfs made on it. Granted, if > you happen to have a scope and detailed knowledge of hardware, you can make > a bitmapped screen out of sprites with the thing (a friend of mine actually > did this). But trying to do anything using the "obvious" approach generally > lands you into trouble. Nearly every commercial video game is doing squirrely little things with the VIC chip. Like reprogramming things based on raster interrupts (life was tough without a coprocessor), diddling with graphics modes on the fly, etc. Many of these things required hand-timed timing loops to work correctly. I don't think you'll be able to do all of this, in real time, without some hardware assist of some kind. The VIC will definately be hard to emulate. And the 6502, while not in itself hard to emulate at full speed from an instruction-functional point of view, may be hard to eumlate in real time from a memory cycle point of view, which is just about what you'd have to do to get things like interrupt initiated timing loops to work correctly. Still, I'd like to see a good attempt at it. > How we'd do the sound is anybody's guess. Actually, a good portion of the SID's sound could probably be emulated. For one thing, the SID doesn't have an interrupt output, so there's really no feedback from the SID to the processor for sound related things. The SID analog ports might be a bit tougher, but they're not used much, and I don't think hooking the Amiga mouse into the SID emulation such that it looks like a 1351 mouse would be much trouble. > Sounds like a major commercial project. Who wants to be first? We're still hearing rumors, though still nothing in real life... > ________ ___ Leo L. Schwab > \ /___--__ The Guy in The Cape > ___ ___ /\ ---##\ ihnp4!ptsfa!well!ewhac > / X \_____ | __ _---)) ..or.. > / /_\-- -----+==____\ // \ _ well ---\ > ___ ( o---+------------------O/ \/ \ dual ----> !unicom!ewhac > \ / ___ \_ (`o ) hplabs -/ ("AE-wack") > ____ \___/ \_/ > Recumbent Bikes: "Work FOR? I don't work FOR -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ __ ____ ____ _____ _____ _____ Dave Haynie /// / _ | / __ \ / _ \ / _ \ / _ \ Commodore Technology /// / / | | /_/ | | | | | | | | | | | | | | |\ /// / /__| | ____/ | | | | | | | | | | | | | |\\/// / ____ | / ____/ | | | | | | | | | | | | \\// / / | | | |____ | |_| | | |_| | | |_| | {ihnp4,etc.}!cbmvax!daveh \/ /_/ |_| \______| \_____/ \_____/ \_____/ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~