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I was curious about this passage from the FAQ: >"Is it truly a "discrete 6502?" Not in the strictest sense. However, it really depends upon how picky you would
by bogomipz 6y ago
I was curious about this passage from the FAQ:
>"Is it truly a "discrete 6502?"
Not in the strictest sense. However, it really depends upon how picky you would like to be.
The MOnSter 6502 uses the original dynamic NMOS logic design, implemented at the individual transistor level.
Dynamic NMOS requires a large number of "transmission gate" transistors that are used to switch currents. For various technical reasons, only a 4-terminal MOSFET can make an effective NMOS transmission gate. Unfortunately, individually packaged 4-terminal MOSFETs are no longer commercially available. However, they do still make arrays of 2 or 4 MOSFETs on a single chip with a separate substrate pin. We used the 4-pack version — These are the quad transistor array chips that we mentioned earlier.
Because these transistors do share a pin, there are (strictly speaking) integrated circuits in the MOnSter 6502. However, one might credibly argue that it is a discrete transistor design since there are not (for example) any logic gate chips in the circuit."
Is a shared pin really the big distinction? On a discreet circuit surely multiple components still share the metal traces on a PCB no? Perhaps I'm misunderstanding the meaning of discreet CPU?
- compiler-guy 6y agoA discrete cpu means "no integrated circuits". So the question answer on "does a piece of silicon where the transistors share a pin count as an integrated circuit?" By the most strict definitions, it does count as an integrated circuit. But really, not _that_ integrated.
- bronson 6y agoDiscrete parts have one electrical component per package. A surprisingly good description at pcmag: https://www.pcmag.com/encyclopedia/term/discrete-component https://www.pcmag.com/encyclopedia/term/discrete-component Because the Monster 6502 uses 4-transistor packages, they can't claim their design is 100% discretes. However, these are separate transistors with a shared substrate. It's not easy to call them integrated circuits either! It's a gray area.
- jacquesm 6y agoTo muddy the waters further: early 'integrated circuits' were actually thin film circuit boards with discrete components on them wired together for common functional blocks. They either had all their pins on one side allowing for vertical mounting or the now much more common dual row of pins.
- dmitrygr 6y agoLooking for 4-terminal MOSFETs in a deep rabbit hole, so let me safe everyone else the trouble: MIC94031, SST215, MIC94051, SST213, MIC94030, SST211. $3+ ea