Skip to main content

New answers tagged

1 vote

Why didn't CPUs multiplex address pins like DRAM?

As others noted, the 1802 (which I used to wire wrap my first computer) multiplexed the high and low address bytes. But it was slow, even compared to CPUs of its day, using eight clocks per machine ...
hawk's user avatar
  • 161
2 votes

Why didn't CPUs multiplex address pins like DRAM?

By way of an aside, IIRC, all of Digital's single chip VAX processors multiplexed the 32 bit address and data busses onto one set of 32 pins (the Data and Address Lines, or DAL).
Shaheed Haque's user avatar
5 votes

Why didn't CPUs multiplex address pins like DRAM?

Most modern CPUs do indeed do this -- they have memory interfaces that connect directly to DDR SDRAM, and can be configured to match the specific memory chips in use. The transistors required to do ...
Dave Tweed's user avatar
  • 1,804
17 votes
Accepted

Why didn't CPUs multiplex address pins like DRAM?

TL;DR: It's all about when which information is needed DRAM uses addresses differently to other components, due to the way it's organized. To access a memory cell, DRAM needs to address first a row ...
Raffzahn's user avatar
  • 225k
10 votes

Why didn't CPUs multiplex address pins like DRAM?

This is for the 6502 and 68000 days you're asking about... For a microprocessor (MPU), using multiplexed address lines slows memory access down. MPU performance was a/the major selling point for the ...
TonyM's user avatar
  • 4,268
10 votes

Why didn't CPUs multiplex address pins like DRAM?

Many CPUs did have a multiplexed bus, but not in a way compatible with DRAMs that mux the address bus. CPUs that had multiplexed bus usually multiplexed half of the 16-bit address bus bits with 8 data ...
Justme's user avatar
  • 33.7k
17 votes

Why didn't CPUs multiplex address pins like DRAM?

Many CPUs did multiplex address pins in a variety of ways. Multiplexing address pins with each other, as was done on e.g. the CDP1802, means that unless the CPU multiplexes things in the exact same ...
supercat's user avatar
  • 37.1k

Top 50 recent answers are included