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Hello, I am working on a homebrew TTL stack computer design using 74LS series chips. I recently created a single board version of the computer with an integral 50 channel bus. My computer is clocked at 1 MHZ. I have made provision for a bus-out connector, anticipating that I might want to...

Here is a programming language checklist for people writing a new computer language. It's both funny and true... https://www.mcmillen.dev/language_checklist.html Here is an excerpt from the header: You appear to be advocating a new: [ ] functional [ ] imperative [ ] object-oriented [ ]...

Hi, I have been reading about, and playing with a C Language Interpreter called "RUN/C Professional" as was offered by Lifeboat Associates in the 1980's, and as reviewed here: https://www.softwarepreservation.org/projects/interactive_c/bib/Unger-1987.pdf I was able to find a disk image of the...

Hi, I am watching for an "ACER" badged Keyboard that has the 5 Pin large DIN connector with PC/XT output (Not AT). This would be before a "Windows" key was on the layout. Some of these keyboards have a slide switch on the underside to select PC/XT or AT. This is for an ACER 710, an IBM PC clone...

This is an IBM 5155 PC Luggable that is for sale and available for pickup only at the Monroe County Hamfest on Sunday, June 18th beginning at 7:30 AM. I have had this machine for over 20 years and don't remember where I got it. First attempt at boot showed a memory check that stalled, and 2nd...

Hi, I have been building and testing a homebrew 8 bit machine running at 1 MHZ called LALU (Lookup Arithmetic Logic Unit). One of my goals was to benchmark the machine using a method to calculate prime numbers up to 1000. Sometimes you will see this referred to as the Sieve of Eratosthenes...

Hi, I am hoping someone can help with this... I seem to recall that there are some coding shortcuts for converting the ASCII character representation of a number to the actual number. For example the ASCII character Hx39 "Character for 9" represents the number decimal 9, and the ASCII...

Can anyone suggest a good reference which explains the operation of the ALU component of the 8088 CPU? Is that design out there somewhere? Thanks! Michael

Hi, I am in the process of building and improving a homebrew computer design that uses programmed ROMS for the Controller and ALU. The computer is called LALU, for "Lookup Arithmetic Logic Unit". The computer architecture has an 8 bit data bus, and a 16 bit address bus. The basic architecture...

Hi, I am doing some coding in GW-Basic for an XT compatible running DOS 3.3. I have a program that parses latitude and longitude from a GPS module connected to the COM port. I would like store the location information in the DOS system enviroment such that the location is available to other...

If you enjoy vintage computers you might want to consider getting into the homebrew building hobby. For about the past 2 years I have been building and coding a homebrew TTL Stack Computer called the TTL-Retro. I built the computer from scratch using TTL Integrated Circuits, and the computer...

Hi, During the past year I built a TTL computer from scratch and now I am in the process of writing a custom programming language for it. My machine has dual hardware stacks: Return and Data. I was having a hard time understanding how Forth works 'under the hood'. I recently found a terrific...

Hi, I am building a TTL computer using the 74F181 ALU. I am fairly far along in the project and I am coding now in machine code. One of the things that has come up as an issue pretty quickly is that there is no right hand bit shift available. The ALU has the usual ADD, Subtract, Increment...

Hi, I am in the process of writing an assembler on a custom homebuilt TTL computer. The computer does not have a CPU. The control logic is hardwired and uses the 74F181 ALUs for math and logic computations. The I/O consists of an APPLE II keyboard keyboard capable of direct ASCII output...

Hi, I have built a homebrew computer using TTL IC's according to the architecture described by Eckert in his paper "Microprogrammed Versus Hardwired Control Units: How Computers Really Work". The architecture is shown in the attached diagram. It is a fairly basic machine with a 12 bit bus...

Hi, I am building a simple computer for fun that uses the 74181 Arithmetic Logic Units. These ALUs were the basis of some of the older vintage computer designs. I am trying to identify a Register part number to use for the Accumulator (ACC). A unique feature of the ACC is that it stores the ALU...

Hi, I recently was able to obtain 3 pieces of the Harris RTX-2000 CPU. This CPU has been used on numerous spacecraft by NASA, and in various embedded or development cards for computers in the early 1990's. (For example by Silicon Composers.) I would like to create a PCB to do some development...

Hi, Lately I have been toying with the idea of building a stack machine computer. This would require a CPU that has more than the rudimentary stack operations of Push, Pop, etc. My research has led to the RTX2000 and RTX2010 CPU's that have been used for spacecraft and other specialized uses...

Hello, I have searched extensively for a copy of the IBM manual(s) for the UCSD P-System. (This was an alternative operating system to DOS and CP/M for the original 5150 PC). Does anyone have a copy, either electronic or physical that could be shared, sold, etc? Thanks! Michael

Hi, I have a 3C503-16-TP ISA Network Card (Etherlink II/16TP) and I am trying to find and use the shared memory space on the card in a 5150 PC. The card has a 16K boot ROM socket with selectable addresses (C8000, CC000, D8000 and DC000). The ROM socket is empty. I've read that this card has 8K...