Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!swrinde!ucsd!mvb.saic.com!ncr-sd!se-sd!cns!dltaylor From: dltaylor@cns.SanDiego.NCR.COM (Dan Taylor) Newsgroups: comp.sys.amiga.programmer Subject: Re: Lemmings - a tutorial Part V (last) Message-ID: <884@cns.SanDiego.NCR.COM> Date: 2 Apr 91 23:24:22 GMT References: <23788@well.sf.ca.us> <23837@well.sf.ca.us> <781@tnc.UUCP> Organization: NCR Corp. SE-San Diego Lines: 45 In mykes@amiga0.SF-Bay.ORG (Mike Schwartz) writes: >I also use OS calls to find out how many floppy drives >are connected, where any FAST memory is, and what kind of CPU the >machine has. >The first thing the Kernel does is to copy itself down to low >memory ($200). >I should >also point out that immediately after copying itself down to low memory, >I can put graphics screens and the stack anywhere I want. For a 16 >color game, I put the stack at $80000 and a screen at $78000. The >stack needed for any program I write is < 512 bytes. The resulting >memory map gives me from $100 to $78000 to squeeze the game into. And Why, if you have done the checking that you claim, do you SLOW down games that are running on expanded/enhanced machines? If you've taken over the hardware, you certainly DO NOT want your vectors in low memory, if there is a 68010, 68020, or 68030 installed, since they can relocate them using the VBR. On any Amiga with an 020 or 030, why put ANY code or non-CHIP data into anything but 32-bit RAM? You get to use the absolute address modes, which are SLOWER than the register relative modes??? It seems to me that a couple of "movem"s at various the various entry points in you coroutine loop, would allow easy access to all the registers you need at any point in the program. >I also get the benefit of putting my variables in low memory. You >see, the 68000 allows you to use absolute short addressing mode >to access these, which frees a register for other things. So, you trade a spare register, for FORCED contention between the blitter and the CPU. What's the saved cycle trade-off in wait-states vs address- mode calculations, especially given that address-register-relative, WITH displacement, has the same ac time as absolute short? It almost seems that you are trying to prove Mike Farren's point for him. You just do not WANT to use the OS, if it IS possible, so you won't even try. Well, you can program in whatever style you choose, but my MONEY will be spent on games programmed in the style that I choose. Wouldn't you, and your publishers, like to get some of it? If so, help me by writing what I'll buy, rather than what you want. And even the avid gamers that I know are tired of trashing their environment, so they are not buying much, if anything. Dan Taylor * My opinions, not NCR's. *