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24

The 8051 is a Harvard-based microcontroller, Not really. It's a modified Von-Neumann design with non overlapping address spaces for program, data and I/O. There is no simultaneous access to program and data at the same time, which is the basic feature for any Harvard design (*1). A modified Von-Neumann architecture combines the (software) advantage of ...


23

So I've read all the answers written before my own and they all IMHO are more or less missing the main point. 8051 can have a single monolithic external 64kb address space, that is both written, read and where the instructions are also fetched from. Having peripheral devices somewhere in that space is also nothing new, known from pdp-11, continued in 68xx ...


9

Even if wired into a system that allows programs to be run from external RAM, the 8051 architecture is designed to allow quick operations with up to 256 bytes of internal RAM and internal I/O. Accesses to anything outside that range are much slower. This is great for applications which spend most of their time dealing with internal I/O, but not so great ...


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I'll keep this answer relevant to retrocomputing. The remaining aspects of your question belong in Electronics.SE. Without getting into those particulars, you ought to know that these chips are not at all related. One is not the ancestor of the other. They are entirely different architectures. The 8080 was the CPU for the Altair, the first popular ...


4

While internally the 8051 is actually a stored program CPU, to the programmer and hardware designer, it behaves as a Harvard machine which separate program and data memories. Because of this, programs can only execute from program memory. Critically, there's no built-in way to modify program memory. Even if you stored the program in RAM, there are no ...


2

No DMA to do video A video controller chip needs immediate access to video RAM when it is outputting a row. To this end, microprocessors provide a pin that holds the processor and releases the buses. The process is called "Direct Memory Access". The 8051 has no provision for DMA. It's not intended for systems which are that complicated. The ...


2

i8051 used shared buses which mean for simple connection of a memory you would need latches and some logic to select between RAM/ROM chips etc. That means more complicated circuitry and more ICs for design. Also the i8051 architecture is more suited for static programs in EPROM/EEPROM instead of in RAM. So a native bus driven CPU was the usual choice over ...


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