Brendan wrote:
Hi,
davidv1992 wrote:
@Brendan: I redid the calculations for those, and still arrive at the same numbers. However, do note that I am planning only 8 RAM boards (so 64 bytes) at the most, precisely because they take so many transistors. That reduces the part count for those to about 2700 transistors. That still is more than half of the total number of transistors used, but given the minimalist nature of the rest of the processor, that is not unreasonable.
The 16 boards you are most likely referring to are ROM boards, which only need a single diode per bit, and then only if that bit is actually on (or off, depending on which set of datalines I decide on using to perform reads). Those boards need a lot fewer transistors as a result of that.
Considering that something like "x << 4" is going to consume 4 instructions (and I assume at least 4 bytes) your RAM and ROM sizes are going to be very limiting - so limiting that (from an economics perspective) it'd probably be more viable to not have any CPU and just have "program boards" containing special purpose logic (e.g. maybe a little like
Magnavox Odyssey).
I'm also wondering why discrete transistors (and why not something like
7400 series logic gates). Creating one logic gate from transistors sounds like fun the first time, but after that it'd quickly become a tedious chore.
Cheers,
Brendan
To be quite honest, from an economics perspective, this entire project (even with special purpose logic program boards) can be called not-viable. I have started to look into the Odyssey, and that kind of design, I am not sure it is something i'm interested in, but it looks intriguing. Thanks for mentioning/suggesting that.
Taking inspiration from special purpose logic boards, I could (in the future) potentially build special purpose memory boards that carry out such operations. Using that, something like x << 4 could be done in 2 instructions, and if such a special purpose board used one of the two low memory slots those instructions would take only 2 bytes.
On the why discrete transistors, for one I am one of those persons that likes the sort of tedious chore of repeatedly soldering the same thing. Also, I just like the idea of having designed almost everything myself (with the exception of the transistors and resistors that is), and being able to reduce the number of active components to an absolute minimum.