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Re: 6502 board resistor networks
I agree with your statements - I think there can be some relaxation of
some things. Some parts
are difficult to come by now and I would hate to discourage new people
from participating because of
that - so there has to be a balance. Not all participants are
electrical engineer types so it can be
frustrating to them not knowing where they can substitute.
On Jan 12, 10:59 am, "j....@cimmeri.com" <j....@cimmeri.com> wrote:
> 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
> lynchaj wrote:
> > 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 <y....@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