sburrow wrote:
You do like wire-wrap it seems! What advantages have you found using that, vs breadboards or soldering? I have never wire-wrapped, but I figure it is a good in-between, having the durability of soldering but the ease of breadboards. Am I right?
Hi Chad! That is a multilayered question! I think, first of all, there's a kind of aesthetic component: I enjoy doing the wire wraps. The best analogy I can think of is tool sharpening. I really like sharpening my hand tools with old-fashioned oilstones. I like the stones, the oil, the sound and feel, the smell. Some people really hate sharpening and look at it as a chore they want to get over with as quickly as possible. Other people see it as a kind of meditative activity to be done at the end of the day in the shop and looked forward to as a nice way to finish up. Wire-wrap for me is more like that second group; I'm perfectly happy to sit in silence in my workshop for hours making wraps. It's very satisfying when you get good ones!
That being said, there are some frustrations with wire-wrap, primarily related to the wire. Kynar wire is really hard to strip compared to other wire, and quality control seems to be hit or miss. My first spool (50 feet of blue wire) required a bit of effort to strip, and I would occasionally mess up a wire. But my second spool (1000 feet of white wire I got on sale) is like a totally different thing. Often it WILL NOT strip, and just snaps off in the stripper. Or sometimes the bare wrapping part of the wire refuses to turn and breaks off in the wrap tool. It seems like the insulation thickness, wire thickness, and "adhesion" between them is really inconsistent along the length of the spool. It's not uncommon for me to waste 3 or 4 wires before I get a good one. This is annoying, because this wire is expensive! Faults can also be hard to spot. Yesterday I was doing some initial testing with my scope, and the R/W\ line appeared to be grounded. I couldn't see anything wrong, but I replaced that wire and R/W\ suddenly started working, so I must have had a bad wrap.
When it comes to soldering, I have gotten a lot better at it since becoming an electronics hobbyist. I enjoy soldering if it means putting a pin through a hole, soldering it to that hole, and having it be instantly connected to the things it needs to be connected to by strips on the project board. I don't mind bending component leads around to make more distant connections if I have to, but I generally despise point-to-point soldering on pad-per-hole perfboard where you have to try and get two or three different things through the same hole and hold them steady while soldering. I especially loath plated through hole. I do make mistakes, and it's just nearly impossible to get the solder in the hole heated up enough to use the solder sucker without lifting the pads off the protoboard. I had this problem frequently with Blue April (my first foray into soldering hobby electronics) and it was really frustrating.
As far as durability goes, I think both methods are fine for hobby projects if you do them right. Wire-wrap took us to the moon and gave our high end fighter jets RADAR, so it's probably fine for my hobby computers!
As far as breadboards go, I love my breadboards, and have learned how to get good results with them. However, I don't look at a project on breadboards as finished. For me, breadboards are a kind of sandbox. I wouldn't build a thing on a breadboard if I already knew exactly how it worked. (You know, those projects that are like following a recipe: you buy the components, solder them together in order, and boom, you have a computer.) Breadboards are so I can do hands on experimentation... how does my VGA circuit behave if I reset the line counter on HBLANK rather than HSYNC? What does my clock signal look like with AHC logic vs. HC logic? My breadboard VGA "card" is about twice the size of the project box I have to hold Blue August, so if I want Blue August to have VGA I will have to make a wire-wrap version of that too.
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What software have you been thinking of running on it? I personally have found that an important question early on, as it decides: how much RAM vs ROM you will have available, what your I/O will look like, etc. I know you are capable of 80-column text, so will this be used for programming or text games? Will all of the software be on ROM, or will you have some other storage device (like an external hard drive or SD card)?
This will be like an expanded version of Peanutbutter-1. It has the same 128-byte movable I/O window, so that it can be configured for I/O in Zero Page if you want that. It also has 64K of SRAM and 128K of Flash ROM (in four 32K banks) using the scheme discussed in the "Period Appropriate" thread. The ROM bank will be selected by front-panel switches, but RAM can be banked in and out by software writing to a register, so it can boot from ROM, copy ROM to RAM, then run from RAM. I should be able to run PAGIMON on it with minimal effort. I haven't done a serial port yet, so I plan for the first I/O board to have an ACIA on it. I might see if I can get it to run Ben Eater's port of WozMon over that. In the long run there will, of course, be VGA text. A long-term plan I have had for a while is to eventually study Doug Comer's XINU book and port it to the 6502. I also have Loeliger's "Threaded Interperative Languages" that I would like to study and create a FORTH-like environment. It can live in a different ROM bank from the XINU boot loader so you can choose your execution environment with the flip of a front panel switch!
As far as mass storage goes, I'd like to give it a filesystem on Compact Flash. I already have a leftover IDE / CF adapter that has the right kind of pin header for interfacing to breadboards and IDC connectors. That's a bit in the future though; I don't know much about filesystems, so I'm not sure how challenging that project will be.