Reverse engineering old chips Ken Shirriff

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Sinclair Scientific Calculator (1974) Reprogrammed TI 0800 4-function calculator chip to support trig, log. How? Image: Ralf Pfeifer at de.wikipedia, CC BY-SA 3.0 Now for something different. TI built a simple four-function calculator chip. The code for the calculator was crammed into 320 words. Sinclair reprogrammed this chip to make a cheap scientific calculator. How is it possible to fit trig and logs into a chip that barely fits basic math? I reverse engineered the chip to find out.
TMS 0805 calculator chip siliconpr0n.org John McMaster took a die photo of the chip. You can see some of the features we’ve discussed: the pins, registers, ALU, instruction decoding. This chip is built for calculators: so decimal arithmetic, 11-digit registers, 7-segment display driver.
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Reverse engineering old chips Ken S
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Z80 (1976) Brq Wait Bak Wr Rd Irq M
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Instruction decoding PLA Instructio
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MOS transistors Drain Gate Source
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NAND gate +5 +5 Out 0 Out 1 1 Input
Page 11 and 12: NAND gate +5 Inputs Output Transist
Page 13 and 14: Gates get weird in the ALU +5 Out 4
Page 15 and 16: Sinclair Scientific Calculator (197
Page 17 and 18: Can see bits in the 320-word instru
Page 19 and 20: Intel shift-register memory (1970)
Page 21 and 22: More info: righto.com/shift
Page 23 and 24: Collector Collector Base Base Emitt
Page 25 and 26: What bipolar transistors really loo
Page 27 and 28: PNP transistor
Page 29 and 30: Interactive chip viewer More info:
Page 31: 741 op amp
Page 34 and 35: More info: righto.com/741
Page 36 and 37: 7805 voltage regulator 7-25V in 5V
Page 38 and 39: A family of regulators from one chi
Page 40 and 41: Stitch photos together for high-res
Page 42 and 43: Motorola 6820 PIA chip
Page 44 and 45: Easy way: download die photos zepto
Page 46 and 47: Current project: 8008 analysis
Page 48 and 49: Reverse engineering old chips Ken S
Page 50 and 51: Z80 (1976) Brq Wait Bak Wr Rd Irq M
Page 52 and 53: Instruction decoding PLA Instructio
Page 54 and 55: MOS transistors Drain Gate Source T
Page 56 and 57: NAND gate +5 +5 1 Inputs 1 Out 0 0
Page 58 and 59: NAND gate +5 Inputs Output Transist
Page 60 and 61: Gates get weird in the ALU +5 Out 4
Page 64 and 65: Can see bits in the 320-word instru
Page 66 and 67: Intel shift-register memory (1970)
Page 68 and 69: More info: righto.com/shift Here’
Page 70 and 71: Collector Collector Base Base Emitt
Page 72 and 73: What bipolar transistors really loo
Page 74 and 75: PNP transistor PNP transistors are
Page 76 and 77: Interactive chip viewer More info:
Page 78 and 79: 741 op amp On the die you can see t
Page 80 and 81: Current mirror “Clone” a curren
Page 82 and 83: Unusual current mirror transistors
Page 84 and 85: Vin Gnd Vsense Vout Here’s my die
Page 86 and 87: Die photos: Metallurgical microscop
Page 88 and 89: Hugin takes some practice Tip: have
Page 90 and 91: How to get to the die? Photo: zepto
Page 92 and 93: Acid-free way: chips without epoxy
Page 94: Blog: righto.com ken.shirriff@gmail
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Reverse engineering old chips Ken Shirriff

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