I decided to build a nine-bit computer

Re:I decided to build a nine-bit computer by mad_ned on Wednesday February 09, 2022 @09:19AM (#30272871)

haha yes, excellent suggestions! I did think about ternary logic actually but I don't know of an FPGA that supports it. I considered creating like a primitive that burns 2 register bits to approximate it even, and just throw away the 4th state and pretend I have 3-state logic on all the layers above. but i have enough on my hands just trying to get the stupid timing working on a simple CPU. Im not actually a CPU designer so I dont really know what I'm doing lol.

[ Parent | on HN ]

Re:I decided to build a nine-bit computer by enriquto on Wednesday February 09, 2022 @09:44AM (#30273156)

Throwing away 25% of your bits sound wasteful... what you need is a moderately large power of 2 that is very close to a power of 3. These can be found by computing the continued fraction of log(3)/log(2). The sequence of convergents starts thus 2/1, 3/2, 5/3, 8/5, 11/7, 19/12, 46/29, 65/41, 84/53. Some good choices seem to be 2^8-3^5=13 (loses 5%) or 2^46≈3^29 (loses 2.5%).

[ Parent | on HN ]

Re:I decided to build a nine-bit computer by amelius on Wednesday February 09, 2022 @10:21AM (#30273609)

You can also detect Z state by driving the input high, reading, then driving the input low, reading. If both reads are different, then you have a Z state. Otherwise, the input is the read state.

Of course, drive the input through a resistor.

[ Parent | on HN ]

Re:I decided to build a nine-bit computer by buescher on Wednesday February 09, 2022 @01:34PM (#30276407)

This is a fantastic hobby project. Have you thought about doing something with the "extra" bit along the lines of tagging bytes for type or garbage collection or whatever like the lisp machines?

[ Parent | on HN ]