General QuestionsWhat kind of computer is this?
A very simple one. It may recall the DEC PDP-11 or some other mini from the early 1970's but Heritage/1 will be a lot simpler than that and it won't use ferrite core memory!
Basically it will be a sequential 16-bits digital minicomputer with two's complement arithmetic, a "decent" probation of RAM (about 32 KB) and for storage it will employ some sort of magnetic tapes. Lamps and switches, of course, and RS232 ports to communicate with "Terminals", that is PCs running Terminal emulation software such as Kermit or Hyper Terminal.
It will lack ROM memory. You will be able to turn the computer on without having to wait for the "boot up"; software will be entered from storage after had "typed" a little loader program by the mean of switches. I will really enjoy that part!
What is the point of building an old computer?
My personal motivations -I guess other people had had their own- are basically these two: For one part, I wanted to traverse that frontier that microprocessors represent when we see them as "black boxes": I wanted to write software for a hardware that I truly know up to the wire level. For the other part, I wanted to honor the 1970's computer technology by designing a computer similar to those, build it and -what is more important- to use it for solving problems in the same fashion they did in the past... That will be like time-traveling to the 70s, I guess!
So this project has a lot of cultural as well as technical, hence the severe historical constraints that I have imposed to my self when designing the minicomputer.
Source of Inspiration?
What ignited my desire for getting into this was the Harry Porter's Relay Computer project. That was in May 2009. I spent four days researching and sketching my own solution until I saw that, as fascinate as the project might be, there is no too much room for software in a relay computer.
I turned then to TTL and started to be very influenced by Bill Buzbee's Magic-1. This effort last for one months until I realized that what Bill Buzbee did is far beyond my experience and knowledge on the matter.
Nevertheless these two attempts had exposed me already to a lot of readings and a better understanding on how computers (in general) really work. It also allowed me to approach the matter from the cultural angle which is important.
It was then when I turned to John Doran's D16/M which I recognize as the definite influence for the Heritage/1 project.
What do you plan to use the Heritage/1 for?
I plan, indeed, to use the Heritage/1 minicomputer for doing tangible work. Actually that is an important design principle that I imposed to my self: usefulness. It is important because it sets the difference between a toy and a product... well, she is not exactly a "product", but the fantasy of been so pushes the design toward very interesting directions.
Working in Batch Processing, Heritage/1 could possibly resolve Math problems such as Interpolation, Linear Equations Systems, Fourier Transform and things like that... if I get to write the software correctly, of course...
Time-Sharing? Not necesssarily... I'm not aimed for the nowadays familiar interactive multi-user environments but chances are for that to happen in the deep future, why not? It's all about software. If I get to write the software (including the Operating System), Heritage/1 will be able to run it.
Could I? not sure... time will tell.
What Operating System are you targeting?
I started the current hardware design without any operating system in mind. There was a first attempt last year very influenced by Bill Buzbee's Magic-1 project. I got to dream with porting Minix to my machine as Bill did with his but soon I realized that I don't have the knowledge nor the experience required for such a venture.
So I focused on hardware design for many months until recently that I started to sketch a simple operating system for the computer that I designed. This would be a proprietary multiprogramming single-user operating system oriented to batch processing and magnetic tapes. The simpler the better but (as I've seen so far) no operating system is truly simple...
Have you set any deadline for completion?
I started moving this project by personal motivation instead of dead lines; some days I were so motivated that I spend the whole night working on it; at some other times I were disappointed or lacy so I went to sleep early.
I realized that the project were moving too slowly so I started to set dates for completions, a sort of Project Plan divided into managable phases. According to this plan, a functional Heritage/1 computer (hardware only) would be ready by May 2010. But May came, went away and the machine is still unfinished.
Hence I learned that a project that can only be worked out at free times (which is not too abundant in my life) simply can not be planned in time. What I used to do now is to make "estimates". According to the lastest one, Heritage/1 cannot be finished by this year (2010).
| 
