Skip to main content
Share Your Experience: Take the 2024 Developer Survey
32 votes

How could the Intel 4004 address 640 bytes if it was only 4-bit?

There may only be four pins coming out from the chip but it allowed for more than sixteen values because it multiplexed 4n-bit values onto those four pins based on timing. The instructions for ...
paxdiablo's user avatar
  • 4,857
21 votes

Where can I find more information on the internal architecture of the Intel 4004?

Two IEEE papers written by Federico Faggin, the chief designer of the 4004: The History of the 4004, written by Faggin and three other members of the 4004 design team, for IEEE Micro, Dec. 1996. ...
DrSheldon's user avatar
  • 16k
21 votes

Where can I find more information on the internal architecture of the Intel 4004?

The following references contain more detailed information than can be found in the Intel 4004 datasheets. The MCS-4 Assembly Language Programming Manual (Intel, 1973) has information about the stack,...
JRN's user avatar
  • 1,265
18 votes

How could the Intel 4004 address 640 bytes if it was only 4-bit?

The 4004 used the data bus for both addresses and data. The memory control outputs were used for bank selection. Here's how it works: At the beginning of the instruction, the CPU raises SYNC to let ...
JeremyP's user avatar
  • 11.7k
15 votes
Accepted

Which endian was the Intel 4004?

You can find here the Intel 4004 datasheet. You can see from the 4004 Instruction Set table on page 4 that the 3 nibbles of a jump target address (in ROM) are stored with the highest order nibble in ...
davidbak's user avatar
  • 6,289
11 votes

Pulling my hair out over a 4-bit architecture, there ought to be some law here somewhere, is there?

I would tend to favour "conceptual simplicity" rather than trying to strictly minimise any physical parameter. Observe that some low-cost computers managed to get away with a 1-bit ALU ...
Chromatix's user avatar
  • 16.8k
6 votes

How could the Intel 4004 address 640 bytes if it was only 4-bit?

Both answers of paxdiablo and JeremyP are fine, but if you want a more practical view - though it uses the successor 4040 chip - the British magazine Practical Electronics had a 10 part constructional ...
Tasos Kipriotis's user avatar
4 votes

Pulling my hair out over a 4-bit architecture, there ought to be some law here somewhere, is there?

[preface: This question would need a heave rewrite to really qualify as RC.SE compatible, as so far it may mention some historic architectures, but its core questions are about generic system/CPU ...
Raffzahn's user avatar
  • 224k
4 votes

Pulling my hair out over a 4-bit architecture, there ought to be some law here somewhere, is there?

Amusingly, I posted about my design for a processor that's as simple as possible while still being useful over on the anycpu forums just this morning... Summarising: My design uses 14 standard chips (...
occipita's user avatar
  • 2,367
4 votes

Pulling my hair out over a 4-bit architecture, there ought to be some law here somewhere, is there?

You could theoretically create a system with 3-bit words for the Brainfuck programming language. That language is technically Turing-complete, although quite tedious to program. It is a popular ...
DrSheldon's user avatar
  • 16k
3 votes
Accepted

What is a 4002's "RAM Status Character"?

[...] RAM. It had something called "Status Chars". There were 4 of them per memory line and all were 4-bit numbers which could be set from 0-F. [...] They appeared on every single RAM chip ...
Raffzahn's user avatar
  • 224k
3 votes

What is a 4002's "RAM Status Character"?

Per Wikipedia 4002: 40-byte RAM (80 4-bit data words), and one built-in 4-bit output port; the RAM portion of the chip is organized into four "registers" of 20 4-bit words: 16 data words (...
dave's user avatar
  • 35.7k
2 votes

Pulling my hair out over a 4-bit architecture, there ought to be some law here somewhere, is there?

Answer to update on top: While my angle is to create my own computer using TTL chips I am looking at 6502 block diagrams, at PDP-8 ISA and schematics, as the 4004 and TMS-1000. Then you are looking ...
dirkt's user avatar
  • 27.8k

Only top scored, non community-wiki answers of a minimum length are eligible