Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!zaphod.mps.ohio-state.edu!julius.cs.uiuc.edu!psuvax1!rutgers!rochester!pt.cs.cmu.edu!o.gp.cs.cmu.edu!andrew.cmu.edu!cs4w+ From: cs4w+@andrew.cmu.edu (Charles William Swiger) Newsgroups: comp.sys.apple2 Subject: Re: Faster IIGS Message-ID: <8b0r1dS00Vop8FoFlI@andrew.cmu.edu> Date: 28 Sep 90 15:46:49 GMT References: <517@fawlty.towers.oz> Organization: Carnegie Mellon, Pittsburgh, PA Lines: 59 In-Reply-To: <517@fawlty.towers.oz> >In what area (eg: RAM speed, ROM speed, BUS speed, >Timing problems) is the actual restriction to just >putting a new (faster) 65816 and new (faster) clock >into the motherboard of the GS, letting the FPI (Fast >Processor Interface) take care of slow downs? Putting it simply, all of the above. OK...one of the big problems is that in order to speed up the //gs, you have to replace a lot of chips with faster ones in order to have anything work...just putting in a faster processor and crystal just won't cut it. You would have to replace all of the "fast" RAM with faster RAM (both on the motherboard and get a new memory card with faster chips), you would have to replace the current ROM chip with a faster ROM chip (which can be done, faster ROMs do exist), and you would have to replace most of the address decoding and data bus circuitry. A faster CPU won't do much of anything unless it has faster access to the computer's memory. This is not a home do-it-yourself modification of your computer; it requires a complete redesign of the motherboard. (No hardware hacks allowed ;-) One of the basic limitations of the current system is that all of the slots must run at 1 MHz for the cards to work. The video display also depends upon using 1 MHz RAM in order to keep the video timing on track. Changing the display to use faster memory would be a big help in speeding up the super-hi-res graphics modes. A redesign would also allow the addition of higher resolutions, which would be nice. The //gs uses a 16.7 MHz crystal for the basic system timing, I think, and each processor cycle takes 6 ticks of the crystal to complete. There is also an odd timing problem that forces the 65th processor cycle to be delayed. You're exactly right that having the motherboard sped up would be faster than using a transwarp, that, as you said, uses caching to run the first 2 banks at a faster speed than the rest of the system. By the way, what's wrong with this picture: "In this way you would just get a N Mhz / 1 Mhz machine instead of the 2.8 Mhz / 1 Mhz machine. Where 2.8 > N > 7." In response: "I've had too many tests this week: my brain is MELTING, and I CAN'T get UP!!!" -- Charles William Swiger cs4w+@andrew.cmu.edu