> Is it difficult for hobbyists to design the PCB, etc for a 50MHz machine?
My understanding is that, from 1MHz or so (like a 6502) through to about 10MHz (like an 8086), it's pretty easy to prototype a complete computer — CPU wired to memory, IO, etc, and everything in tolerance to speak to one-another within the CPU's half-clock sample rate — with just discrete logic components (e.g. NOR DIPs to combine address lines to make chip-select pins, etc) on a breadboard.
Get much faster than that, though, and those discrete logic chips start to add too much delay; so you start having to prototype directly for a PCB with surface-mount components, rather than ever having a breadboarding phase. Which sucks, because now you're having to send your design out to be printed and picked, and so your iteration speed is now 1/100th of what it would have been before.
This is, I believe, why many designs back in the day used wire-wrap. A cleanly done wire wrap can apparently get quite clean signal and achieve high frequencies. The Atari ST and Amiga generation machines were prototyped this way, for e.g.. For the ST, 8mhz memory bus but faster for the video shifter portions where the RAM was multiplexed between the CPU and the Shifter.
Unfortunately wire wrap sockets are very difficult and $$ to source these days. Which is too bad because it seems like a good halfway point between breadboarding and PCB.
FWIW I've managed to managed to get clean DVI/HDMI output off FPGA on a breadboard, and I'm by no means talented in electronics.
A lot of modern chips are in the $0.50 to $3 region. So $1 or $5 sockets kinda feels expensive, but I don't think its really cost prohibitive if you're into wire wrapping.
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I think the real issue is that DIP parts / Through Hole parts are completely inferior to their SMT cousins today in 2023. If I want a MOSFET jellybean, I gotta use the 2N7000, which is specified as "on" at 5V (and really prefers to be at 10V Vgs).
Meanwhile, the BSS123 jellybean MOSFET is SMT only, smaller, more efficient, easier to use and easily covers the 3V Vgs common level with today's uCs (STM32, etc. etc.).
Higher performance parts (lower Rds(on), etc. etc.) are similarly SMT only.
When I was last looking 7 or 8 years ago I wasn't able to find a reliable source in those price ranges I'm seeing there. But more than that, I wasn't able to find anything in 40-pin-ish DIP ranges. Just smaller. But especially nothing DIP-64 to fit a 68000 for example.
You can mount SMT parts on breakout boards - although they're designed for breadboarding, in theory you can make those breakout boards compatible with through-hole sockets, so that bridges you to those wire-wrap if that's where you want to go.
If you do use those breakout boards, try to put on these extra-long (.31" + or longer) pins on them. The extra length allows you to wirewrap a bit easier.
All square-posts wire-wrap excellently. The standard pin length is 0.23", barely fitting two wirewraps per pin. Typical wirewrap is 3x per pin, so .31" really helps (and you probably have the extra depth since you're wirewrapping anyway. Its not like these taller pins are much more expensive than the standard pin).
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I think what bothers me about soldering + wire-wrap is that I end up needing to buy Wirewrap tools _AND_ soldering tools. Wirewrap isn't too expensive, but fewer people do it (even fewer than normal through-hole prototypes). There just seems to be far more tools / boards / etc. etc. available that assume soldering.
I think I prefer wirewrap over breadboards or breadboard-like prototypes though. Having the extra height and 3x wire ties per pin "vertically" saves space (at least, board-space), since you're building vertically. Things are definitely more compact than breadboards / breadboard-like protoboards.
But you'll absolutely have to whip out the soldering iron and even use a few specialty tools for a good wirewrapping experience.
T46 pins from Vector Electronics (https://www.vectorelect.com/terminals-wire-wrap.html) and T68 forked-pins pressfit in a "standard hole" (0.042") and also provide more opportunity to wirewrap. You also want the insertion tool btw (one for the T46 pin and another for the T68 pin).
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I guess I've been thinking about my lab recently. I think I've decided (for now) that "wirewrap / DIP" prototyping is for simple one-off projects where 5V uC (aka: Arduino Uno or AVR / PIC chips in general) is fine.
Really, through hole is more than usable at 5V, very pleasant to do even. Yeah, you use up a lot more power than the 3V or lower power parts, but its not that big of a deal.
IMO, prototype at 5V, switch to 3.3V or lower if you need a "better 2nd pass" or something. MCP6002 OpAmps (LM358 if you're going higher voltage), AVR DD is a modern uC still in DIP-28 format, jellybeans like 2N2222 and 2N7000 are boring but they absolutely work. Besides, 5V is USB power and absurdly common in practice.
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If I'm trying to make some project fit inside of 5mW or 0.5mW envelope with a CR2032 battery for power? Okay, sure, I'll build a custom PCB and order those nice and fancy, superior, SMT parts.
If I'm trying to make a microamp meter, and a 1.000mA +/- 0.001mA constant current source one-off project to help me measure the above CR2032 project? Yeah, that's wirewrapping a few MCP6002 OpAmps together + ATTiny.
My damn Fluke 107 has 4.000 Amp +/- 0.001mA measurement. It can't read this other thing I'm doing, lol.
My understanding is that, from 1MHz or so (like a 6502) through to about 10MHz (like an 8086), it's pretty easy to prototype a complete computer — CPU wired to memory, IO, etc, and everything in tolerance to speak to one-another within the CPU's half-clock sample rate — with just discrete logic components (e.g. NOR DIPs to combine address lines to make chip-select pins, etc) on a breadboard.
Get much faster than that, though, and those discrete logic chips start to add too much delay; so you start having to prototype directly for a PCB with surface-mount components, rather than ever having a breadboarding phase. Which sucks, because now you're having to send your design out to be printed and picked, and so your iteration speed is now 1/100th of what it would have been before.