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From: Michael J. Mahon on 23 May 2006 20:00 Eric Smith wrote: > "Michael J. Mahon" <mjmahon(a)aol.com> writes: > >>The 6502 was already a much less expensive processor than its >>competitors, because of a mask retouching technique MOS Technology >>developed that saved mask iterations. > > > I saw that claim on Wikipedia. Is there any published reference? Although the target was dead, the Google cached page at: http://66.102.7.104/search?q=cache:uNXP83T5hq0J:www.commodore.ca/history/company/mos/mos_technology.htm+6502+die+photo&hl=en&gl=us&ct=clnk&cd=5 (sorry about the length) is "The Rise of MOS Technology & The 6502" Written by Ian Matthews of commodore.ca February 15, 2003, Seriously revised and expanded on January 18, 2006. The relevant excerpt follows: >>> In the 1970's, 70% of the industries chip production were defective and therefore garbage. This substantially increases the cost of each viable chip. When a chip is being laid out for etching on a silicon wafer, it drawn at a large scale and then photo reduced over an over again (just like a photocopy reduction) until its microscopic size will fit on the required die. Each reduction layer is called a Mask. MOS figured out a process to repair Masks as they are reduced. The end result was that they had a 70% success rate. This obviously reduced the per chip cost of manufacturing and made the $25 processor a possibility. <<< Frankly, this article (like virtually all technology articles) has enough casual inaccuracies (like spelling Mensch's name Mench), that I can't be sure that this is an accurate rendition of the truth. But is is a plausible story, since repairing a mask master later than the rubylith stage is a time and cost win. -michael Music synthesis for 8-bit Apple II's! Home page: http://members.aol.com/MJMahon/ "The wastebasket is our most important design tool--and it is seriously underused."
From: Michael J. Mahon on 23 May 2006 20:10 John Selck wrote: > Am 19.05.2006, 06:28 Uhr, schrieb mdj <mdj.mdj(a)gmail.com>: > >> Of course, the point remains though that your would never do this on >> the Apple II series, as you'd limit your target market to the earliest >> machine, rather than just the lowest common denominator of all machines >> (64k, 6502 code that's documented and unbuggy) > > > It's easy to do a processor check. It's not easy unless you either 1) know exactly how all machines that your code will ever see behave, or 2) test *exactly* the undocumented behavior that you use--no more and no less. Even in the latter case, you risk the test code being error trapped, so you have to cover that case, too. (Hard if the error trap comes along in the future using an architecture extension that you don't know in the past. ;-) So *both* strategies depend on knowing the future, which, as Yogi pointed out, is diffcult. ;-) -michael Music synthesis for 8-bit Apple II's! Home page: http://members.aol.com/MJMahon/ "The wastebasket is our most important design tool--and it is seriously underused."
From: Michael J. Mahon on 23 May 2006 20:17 Linards Ticmanis wrote: > Michael J. Mahon wrote: > >> Wow--they needed more than a megabyte/second of video data? I guess >> if you have about the same resolution as an Apple II, but twice the >> color depth, then you do... The //c and following Apple II's got >> around this by providing another memory bank in parallel with the >> main memory bank. > > > The C64 mainly needed it for its text mode. Unlike the Apple, the > character shapes reside within the Video chip's AND the CPUs normal > memory map, are read over the normal address bus, and can be redefined > by pointing a register to RAM instead of ROM. > > So once every line of characters the CPU has to stop for 40 cycles, so > that the character numbers can be read and stored. Then during the > normal video cycles only the character shapes are read. Color numbers > for the characters, on the other hand, are read in parallel from a > special SRAM with its own addressing lines going to the video chip. > > The Apple reads the character numbers on every line during its normal > video access, and reads the character shapes in parallel from a ROM > that's not visible to the CPU. Thus you have fixed character shapes.# Of course, the character generator ROM could have been an SRAM, and could have been made visible (byte sequentially, say) on an Apple. It was a conscious choice to make the Apple character set fixed. (And it's nice to have a character set fully defined at power-up.) -michael Music synthesis for 8-bit Apple II's! Home page: http://members.aol.com/MJMahon/ "The wastebasket is our most important design tool--and it is seriously underused."
From: sicklittlemonkey on 24 May 2006 06:36 > It depends on what you do. If you do lot's of graphics and sound stuff, > Java is definitely a bad choice. Ha. You think so? I have friends in the mobile handset game market that would disagree with you. In fact even on the PC it's not "definitely a bad choice". Have you had a look at Java Quake? All this 10 times slower stuff for managed code is nonsense. Tell that to Microsoft, who are betting on .NET binaries compatible across all their platforms. This relates directly to your topic of discussion. JIT compiles at runtime for YOUR processor. Not the lowest common denominator. Cheers, Nick.
From: Cameron Kaiser on 24 May 2006 08:04
"Michael J. Mahon" <mjmahon(a)aol.com> writes: >>The C64 mainly needed it for its text mode. Unlike the Apple, the >>character shapes reside within the Video chip's AND the CPUs normal >>memory map, are read over the normal address bus, and can be redefined >>by pointing a register to RAM instead of ROM. [...] >It was a conscious choice to make the Apple character set fixed. >(And it's nice to have a character set fully defined at power-up.) This is a marginal diversion, but I'm not sure what you mean by "fully defined" since the C64's is, of course, also fully defined in the sense that it's there. :) -- Cameron Kaiser * ckaiser(a)floodgap.com * posting with a Commodore 128 personal page: http://www.armory.com/%7Espectre/ ** Computer Workshops: games, productivity software and more for C64/128! ** ** http://www.armory.com/%7Espectre/cwi/ ** |