Questions tagged [microprocessor]

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6
votes
1answer
303 views

Tannenbaum paper on constants in ISAs?

I see many references to a paper by Andrew Tanenbaum that demonstrated the vast majority of constants would fit into 13-bits, and I seem to recall it being in my university text on CPU design. However,...
2
votes
2answers
188 views

How exactly do all control signals in 6502 work?

I'm trying to make a 6502 replica in Logisim. I want to know what exactly each control signal in 6502, how the clock cycles work and additionally I would like to see an example of these control ...
3
votes
2answers
366 views

Total number of 6502s or 8051s ever manufactured or sold?

What's a good way to estimate the total number of 6502 or 8051 chips (or workalikes, pin-compatible or not, but not including software or FPGA emulators) ever manufactured or sold? Added: (To ...
12
votes
3answers
2k views

What was the first microprocessor to support full virtualization?

Virtual memory, which allows an operating system to run several machine code programs isolated from each other, came to the desktop during the eighties. But full virtualization, which lets the ...
15
votes
5answers
3k views

Why are different emulators needed to run platforms that use 6502 assembly code?

To my knowledge, an emulator turns machine code for a console into something that your computer can understand. For example, assembly code from a Gamecube game is not the same as from a .exe file. ...
1
vote
1answer
435 views

What is the difference between an 8080 and an 8051? [closed]

What are the features of the Intel 8051 architecture that allow it to successfully act as a microcontroller? Hypothetically can the general-purpose 8-bit architecture like Intel 8080 do everything the ...
16
votes
2answers
1k views

6502 branch offset calculation

This question expands on How does the 6502 implement its branch instructions? I'm working on a cycle accurate VHDL implementation on an FPGA. I have much of the program logic already written, but I ...
13
votes
8answers
2k views

Uses for the halt instruction?

What was the halt instruction in early CPUs such as the Z80 and 8080 used for? Here's a description of the Z80 instruction: The HALT instruction suspends CPU operation until a interrupt or reset ...
25
votes
5answers
5k views

How was microcode implemented in retro processors?

How was microcode implemented in retro processors such as the Z80 or 8080? Was the microcode standard (for example a manual for the processor outlining all possible micro-instructions and the ...
9
votes
1answer
347 views

Can we express the instructions to the Analytical Engine in terms of assembler or machine code?

On a recent trip to the London Science Museum I saw Babbage’s Analytical Engine. Apparently this had an ALU (or equivalent). I can build an ALU out of logic gates but I can’t conceptualise how to do ...
42
votes
5answers
15k views

Why did CPU designers in the 70s prioritize reducing pin count?

A lot of 70s era microprocessors were packaged in DIP packages with 40 pins. This was a reasonably good fit for 8-bit processors: 16 address lines, 8 data lines, 2 power and clock are all absolutely ...