Hallo allemaal, Yesterday I opened two different VIC-20's to check what was inside. Then I checked the SCH to see in what addressrange the RAM etc. must show up (I wanted to include mirroring as well). I run into some problems so I need the help of some VIC-20 experts, please. VIC-I: The book says 9000-900F but I have no idea how this is realised. A15..13 are combined into VA13. VA0..12 are mirrors of CA0..12. My conclusion is that some masking is done inside the VIC-I. Your comment, please. VIA's: The book says 911x and 912x. The first selection is done by I/O0 = 9000-93FF. Second selection is made by CA5 or CA4.this means: UAB1 = 1001 00xx xxx1 xxxx UAB3 = 1001 00xx xx1x xxxx 911x and 912x are just a part of the found ranges but then my question is: why not 901x and 902x? Colour RAM: My book, "VIC revealed" by Nick Hampshire, says colour RAM is at 9600 unless there is more than 3K of expansion memory. In that case you'll find it at 9800 (page 112). My SCH says: 1001 00xx xxxx xxxx = 9000-93FF = I/O0 1001 01xx xxxx xxxx = 9400-97FF = COLOR 1001 10xx xxxx xxxx = 9800-9BFF = I/O2 1001 11xx xxxx xxxx = 9C00-9FFF = I/O3 The VIC only needs 506 bytes which would fit in the ranges 9400-95FF or 9600-97FF. So my first guess is a typing error of the author or printer. Your comments, please. Another question: what is the idea behind changing the range in case of more memory? (I cannot see any profit in it) Here is the first result for those VIC-20's to give you an idea how the list could look like: VIC-20 ASSY NO.324003FAB NO. 324002-02 REV.D UAB1 9120-912F VIA 6522 UAB3 9110-911F VIA 6522 UB4 6 * OC invertor 7406 UB7 9000-900F VIC-I 6561 UB6 NE555 UB9 4 * 2-NOR M53202 UB10 D-Flipflop 74S74 UC2 6 * invertor 74LS04 UC3 4 * 2-NOR 74LS02 UC4 3 t0 8 multiplexer 74LS138 UC5 3 t0 8 multiplexer 74LS138 UC6 3 t0 8 multiplexer 74LS138 UD1 4 * analogue switch 4066 UD2..6 1K*4 RAM MM2114-3 UD7 8000-8FFF CHARACTER ROM 901460-03 UD8 8-bit buffer 74LS245 UD9 1 * 13-NAND 74LS133 UE1..6 1K*4 RAM MM2114-3 UE8 8-bit buffer 74LS245 UE10 CPU 6502 UE11 C000-EFFF BASIC ROM 901486-01 UE12 E000-FFFF KERNAL ROM 901486-07 UF8 8-bit buffer 74LS245 U13 4 * 2-AND 74LS08 U14 2K*8 RAM HM6116-4 U15 2K*8 RAM HM6116-4 ASSY NO.250403 FAB NO. 251040-01 REV.D UAB1 9120-912F VIA 6522 UAB3 9110-911F VIA 6522 UB4 6 * OC invertor 7406 UB6 UA555 UB7 9000-900F VIC-I 6561 UB9 4 * 2-NOR 7402 UC2 6 * invertor 74LS04 UC3 4 * 2-NOR 74LS02 UC4 3 t0 8 multiplexer 74S138 UC5 3 t0 8 multiplexer 74S138 UC6 3 t0 8 multiplexer 74S138 UD1 4 * analogue switch 4066 UD2 1K*4 RAM MM2114-3 UD7 8000-8FFF CHARACTER ROM 901460-03 UD8 8-bit buffer 65245 UD9 1 * 13-NAND 74LS133 UE1 1K*4 RAM MM2114-3 UE2 1K*4 RAM MM2114-3 UE8 8-bit buffer 65245 UE10 CPU 6502 UE11 C000-EFFF BASIC ROM 901486-01 UE12 E000-FFFF KERNAL ROM 901486-07 UF8 8-bit buffer 65245 U13 4 * 2-AND 74LS08 U14 2K*8 RAM HM6116-4 U15 2K*8 RAM HM6116-4 The above is not complete, I am thinking about giving each RAM IC its own range. Another question: as you can see, both are D-revisions. Do other revisions exist? Groetjes, Ruud http://home.hccnet.nl/g.baltissen/index.htm - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail cbm-hackers-request@dot.tml.hut.fi.
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