Seems like there's different, perhaps competing, objectives.
One objective is to faithfully recreate legacy designs to build and experience legacy systems that might not be easily done any other way (such as finding a particular real legacy card on eBay). My own interest is in legacy systems, but for example, finding a real legacy 6502-only board has been impossible for me, so the n8vem 6502 board is the next thing.. at least it uses a legacy design and parts. Really, what parts cannot actually be found in some way, unless they were custom like PALs?
Another objective is that of evolving S-100 into more modern designs and operating systems beyond, say, 1986, to beyond where it had gone during non-obsolescence eg. PC compatibility with MSDOS (aside from the CompuPro effort), or Linux. If the intent is to produce a set of whole new designs to delve into these later systems, then these designs could easily have consistent standards across the board. This objective is of no interest to me, but I'm sure many would get a kick of out running newer systemologies on the old S-100 standard.
Though these objectives clash if not clearly defined and left confused, they can in fact be pursued simultaneously... with a clear distinction made between a legacy offering and a new offering.
- John Singleton
Hi Dave, Thanks! I like the idea of consistent design guides however most of our S-100 boards are legacy designs. Most are wholly or partially legacy designs from a multitude of sources. For instance the S-100 6502 CPU board is a PCB implementation of Rich Leary's home brew board used with permission. I tried to be as close to his original design as possible to improve the chances of a working PCB. Similar for the S-100 68K CPU board, I got permission from Alan Wilcox to reuse his design. John has a variety of home brew S-100 boards and design elements from a mixed bag of sources. With so many different designers it is no wonder we are seeing so much variation. Every board has its own story! We do try to have some consistency across boards and reuse design elements when possible but there is still a lot of variation. Many of the boards come with their own unique legacy and are particular to their original designers. As the designs mature, I think we can make them more consistent through respins and tweaks but it will take experimentation and just plain field experience to find out what changes we can make without breaking the board. My personal approach is to be conservative and faithfully replicate the original design as closely as possible. I generally don't stray away from the original drawings especially on the initial version. There are just so many variables in conversion from a home brew wire wrap design to a PCB that broader design consistency tends to take lower priority over basic functionality and reliability. That being said, I think there is a lot of room for improvement as the board designs mature. Consistency is something we can "grow into" or at least reduce the wild variations to something more manageable. Thanks and have a nice day! Andrew Lynch On Jan 11, 10:12 pm, yoda <...@r2d2.org> wrote:Hi Andrew Would it be possible to have some design rules in general. I have seen a lot of these boards use parts that are not easily obtainable which suggests these are copies of old boards without thought. If they are supposed to be pull-up resistors then in general I would expect 1K or 4.7K be specified as they are pretty standard. I checked Jameco, Digikey and Mouser and they don't have 1.3 K. I know experienced people can interpret schematics but it tends to discourage new people into the hobby that don't have that experience. Also it would be nice to do some standardization of buss interface. I see this board uses ls541's where most other boards use ls373's so one has to "stock" many more parts to participate. Just a thought Dave