11–20 of 35 posts
For those who don't know, the name is taken from https://en.wikipedia.org/wiki/Nibble
but also https://futurama.fandom.com/wiki/Lord_Nibbler
Well, he uses a '181 ALU chip -- which is very nice but you have to scour the universe to find vintage logic parts like that any more. Amusingly, it is easier to find vintage vacuum tubes than vintage TTL logic. For that matter... you can find Youtubers building vacuum tubes from scratch using crude home shop tools, which don't quite cut it for TTL logic. For something you could build with today's part catalog, witho…
The system was slower than others in the line, but was also the cheapest.
An intellectually interesting exercise would be to replace all of the logic by a 64bx16b EPROM which loops back onto itself through 2 8b latches. This is possible as the architecture has only 16 bits of state (4b accumulator + 12b PC). This simplifies the hardware, which is nice, but it also makes it a software defined MCU, hence the student could go on to define his own instructionset. Now that would be instructive.
All the logic remaining are bus arbiters and IO access. You can replace 74-181 with one more rom though, but it will not decrease chip count...
EDIT: actually if you replace 74*181 with rom, you can get rid of NZERO flag detection gates (minus 1 chip)...
Has anyone ever written a BASIC for a 4-bit CPU?
I think if you want to get a BASIC running on that 4-bit CPU in the article, the easiest is probably to create a 6502 or Z80 emulator, then run the emulator on the 4-bit CPU.
After all, someone made an ARM (32 bit CPU) emulator for an 8 bit CPU and booted Linux on that.
Also GameBoy first CPU was 4bit based if I recall correctly
So 4bit CPU has something to say.
This is my view on the SSD crashing family of events. Lessons learnt to always be alert and have backups handy.
By the way HP calculators (like 48S was based on a 4bit access-RAM. They was 32bit CPU but first model used 4bit buses. Also GameBoy first CPU was 4bit based if I recall correctly So 4bit CPU has something to say. https://gioorgi.com/2020/hp-42s/
Well, he uses a '181 ALU chip -- which is very nice but you have to scour the universe to find vintage logic parts like that any more. Amusingly, it is easier to find vintage vacuum tubes than vintage TTL logic. For that matter... you can find Youtubers building vacuum tubes from scratch using crude home shop tools, which don't quite cut it for TTL logic. For something you could build with today's part catalog, witho…