Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!mips!pacbell.com!tandem!zorch!amiga0!mykes From: mykes@amiga0.SF-Bay.ORG (Mike Schwartz) Newsgroups: comp.sys.amiga.advocacy Subject: Re: Blitter vs. 040 (was: Computer Architecture question Message-ID: Date: 14 May 91 21:15:45 GMT References: <3310.tnews@templar.actrix.gen.nz> Organization: Amiga makes it possible Lines: 70 In article melling@cs.psu.edu (Michael D Mellinger) writes: > >In article mykes@amiga0.SF-Bay.ORG (Mike Schwartz) writes: > > Again, if you use the 040 to do graphics instead of a blitter, you lose the ability > to do things in PARALLEL with the CPU. The 040 has a limited number of Cycles (yes > gobs of them), and using them for rendering ovbiously gives you less of them for > doing what work your applications do (or your multitasking OS...). > >What am I missing here? You have 15 mips in 1 second or you get 12 >mips the 030 + blitter. Does it really matter if they are running in >parallel as long as the bus isn't limiting you? > The 040 is just as much an option for the Amiga as it is for the NeXt. What you are missing is 15Mips in 1 second PLUS THE BLITTER. Take a course in parallel processing. > The custom chips in the Amiga can and often do cause the CPU to wait when it > accessis CHIP RAM. If the blitter is running in NASTY mode, for example, it will > steal every possible cycle from the CPU (on the CHIP BUS only). If you are using > some of the higher resolution graphics modes (like 640x400x16 colors), the display > hardware steals 100% of the CPU (and blitter) cycles except for horizontal and > vertical retrace. The Amiga workbench is 640x200/400 x 2 planes, because it > steals no cycles in this mode. > >So, the blitter is stealing from the faster chip, the 68030? ONLY if you are stupid enough to deliberately cause this contention. The blitter can have ALL the cycles it wants while your CPU does work not related to graphics. Unlike your NeXt's DSP, the blitter is actually useful a LOT of the time (and both run in parallel). > > Your question about graphics modes shows that you haven't learned much at all > about the Amiga (RTFM, please). To get 640x400x4096 colors, you can use a single > bitplane of 32,000 bytes, but your graphics mode is seriously limited (you have to > do EVERYTHING with the copper). In HAM mode, you can't go 680 horizontal, but you > can open 10 (96K each) 4096 (6 plane) 320x400 screens in 1Meg of CHIP RAM. The Amiga > does support overscan, so you can get hirhger resolutions (I'm using 704x484). > >Yeah, the Amiga has a dozen different graphics modes. That's nice. >It will probably have a dozen more before the Amiga dies. In the mean >time, the blitter is on its way to becoming the bottleneck in the >system, if it already hasn't. > The only bottleneck here is your opinion and not anything to do with reality. You just made my kill file. > The Amiga 500 doesn't even ship with 1Meg of RAM (the 500P does), and it is fully > able to run the entire Amiga OS (multitasking and all), and virtually all applications > for the Amiga (except the very few that require 1+ memory). > >Yes, so what! Are we bragging about how few paper clips we wasted? >Memory is cheap. We just bought 16MB of memory for $650 for our NeXT. >Functionality is more important. On the NeXT we have an OS that >supports 24 bit color, has memory protection, virtual memory, and does >much more. > The only thing wasted is the money you'd spend on a NeXt. If I wanted one, I'd go and buy one, but it isn't even in the least interesting to me. >-Mike -- **************************************************** * I want games that look like Shadow of the Beast * * but play like Leisure Suit Larry. * ****************************************************