30

I believe that your presumption is incorrect: The vendor, having no way of knowing whose fault this is, has to take the machine back and try to debug it. The vendors did not have to take the machine back and if they did offer a repair service it was not free. I don't recall that MITS (vendor for Altair) offered a repair service but I know that Heathkit ...


29

Back in the 80s, it was an industry and market very different from today's PC world. The audience were mainly do-it-yourself people who wanted to create things, and to understand how they worked. So, of your suggestions, "Tradition" best captures that aspect. You'll also find that, in line with that mindset, writing individual programs was a main ...


26

It didn't move anything. There is no ROM at the beginning of memory. As the system did not include any code in ROM at all by default, ROMs were optional and usually placed at the end of memory. ROM is not needed, because the front panel can be used to halt the CPU, enter a program into RAM without CPU intervention, and command the CPU to execute the code ...


26

Did anyone ever put that much memory in an Altair, IMSAI or other 8080/Z80 S-100 bus machine? Has been done a lot of times. Remember, S100 has been used all the way thru the 1980s into the 1990s. RAM sizes did pass the basic 64 Ki already before 1980 and went way beyond 2 MiB soon after. Boards were available by all major S100 supporters, including Cromemco,...


21

Just about a week ago, I encountered the same question as I was thinking about the idea of building a front panel for my homebrew computer, but I didn't understand how could one "move" the CPU to execute code at an user-specified address without affecting other components such as the content inside the RAM, I even searched at RC.SE! And so, I decided to take ...


19

I'm actually not aware of any major 8080 test suites; everything I've ever found has been for the Z80 rather than its parent. That aside, I'd heavily suggest you don't discard the CP/M solutions you've found as they're usually pretty trivial to set up as test cases without any of the main substance of a CP/M environment. For example, to run the CP/M version ...


18

if every machine will be sold preassembled, the vendor can invest in things like wave soldering equipment that can do the job much more efficiently than a user doing it once on the kitchen table I think this is a key point. Back in the 1970s, you did not have the super-cheap build-it-in-China and ship extremely inexpensively that you have today. Container ...


16

If you count Altair clones, yes. For the original Altair 8080, quite possibly (if the PSU was capable of powering eight of the IMSAI memory boards along with the CPU and I/O boards) and for the Altair 8080b, almost certainly (it had a more powerful PSU). IMSAI did pretty much exactly what you suggested in your question, but a year earlier than the date you ...


15

Many early computers were sold as self-assembly kits Not really. There is a visibility bias. Kits were simply more visible than ready made machines. Kits were simply the best way to fill pages of magazines - and that's what most people saw and still find on the net - thus they got more 'screen time' than ready units. Especially early on, when there were no (...


15

The standard (IEEE 696) is available here Section 1.1 defines the scope of the standard as Data exchanged among the devices is digital. A maximum of 22 devices are interconnected. The total transmission path length does not exceed 25 inches The maximum switching rate is 6 MHz.


12

As Wikipedia says (S-100 bus): "(Author) then looked for an inexpensive source of connectors, and he came across a supply of military surplus 100-pin edge connectors. The 100-pin bus was created by an anonymous draftsman, who selected the connector from a parts catalog and arbitrarily assigned signal names to groups of connector pins." So the ...


11

Simply put, for most of the PC's history, either the components were roughly uniform in their power consumption (with the major offenders typically being the 12V motors in disk drives, rather than anything solid-state), or the CPU was the major power consumer and thus source of heat. Only fairly recently has one particular type of expansion card, namely the ...


11

Lately I found myself wondering what hardware was required for the Altair to get BASIC up and running. Basically Cage CPU-Card with 1 KiB RAM 4 KiB RAM Card Serial Interface To have some space for any user program second 4 Ki card would come handy. And in fact, this is as well the configuration for which BASIC was offered at a lower price: 75 USD ...


9

Never used nor saw an Altair so I might be completely wrong in here. However this doc for some Altair 8800 contains the circuits (at the end)... The power supply is divided to 2 zones. one with transformers and rectifiers and second with voltage regulators. My EE skills are telling me the start race of -16V wins due to input RC filtration filter has smallest ...


7

TL;DR: SWTPC and their 6800 system did sell quite well and over a longer time than all of its competition. The question is rather why do most people only know MITS/Altair, which I'd say is rather a hype in hindsight - plus the same effect that made the PC ubiquitous: Cloning. The Long Run When considering 'success' of a single machine or manufacturer it is ...


7

How exactly does it load the program counter, given that there's no obvious way to tell the CPU to do this without excecuting instructions to do so? Seams like you know it already :)) Does it actually put instructions on the bus and get the CPU to execute them? That's exactly what is done: Let the CPU jump to that address. In case of 'EXAMINE' the ...


6

It has a button on the front panel to single-step the CPU one instruction at a time... Except that, on closer inspection, that's not actually what it does. Exactly, and it's not what the button is intended to do. The purpose is not to single step an instruction, but to single step a cycle. That's a slightly strange way of doing things. No, it's exactly ...


6

The main means of thermal dissipation are convection and radiation (and flow). Convection is used always and independent of orientation. Board setup of the era have been made in any direction. Putting boards close and in parallel is, independent of orientation, not a great idea at first, as they heat each other (by radiation). This means for thermal ...


5

I strongly suspect CP/M was the key. Plenty of 8080 (and by extension, Z80) machines ran other operating systems, particularly the Radio Shack TRS-80 line. But the basics of Altair, Imsai, Osborne, Kaypro, NorthStar and so many others promoted the Intel 8080/compatible market in a huge way. CP/M led to mass-market business software like WordStar, dBase II, ...


5

[...] So I need to find an emulator of the MIT Altair 8800 with Intel 8080 processor inside. Then where can I find and download its emulator for Windows. I have tried to search over the net [...] Not sure where you searched. If I just start entering MITS ALT... Google already offers to autocomplete with "mits altair 8800 emulator", resulting in a reasonable ...


5

The difference is the 2 years from 1975 to 1977 (when the Apple and TRS-80 came out). A 1975 Altair was programmed in opcodes using toggle-switches, and the output was flashing lights. Whee. By 1977 we had video, BASIC, keyboards and the ability to save programs on tape. The only reason to get an early 1975 Altair was to mess around with it as a technical ...


5

It looks like the Altair 8800 didn’t have any provisions to ensure -5V was available first (but see @Spektre’s answer and the note below). I found a schematic of the Altair 8800 CPU board power supply in this document, page 20. This shows a very primitive -5V supply (just a resistor going to the unregulated -16V supply, a 5.1V Zener and a some capacitors for ...


4

At the time the numbers of unit made were was smaller than today, and technology for assembly electronics was way less advanced than today. Was a labour-intensive process so shifting the work to the end user made sense, especially if the end user was an amateur without a lot of money, but some spare time and a love for electronics. Add to this that was a ...


4

A single example, but a neat one: Josh's 12-byte Microsoft 4K BASIC bootloader. Kind of needs a paper tape reader and 4K BASIC, but does save your fingers from those fiddly wee switches!


3

Predictable volume was an unknown. This stuff was so new, nobody knew how many would sell. And for many who dared make them, market estimates were way off. Mass manufacturing requires knowing the volume so that the tooling investments can be amortized. Tooling for manufacturing also adds lead time, by which time you might be "scooped" by some ...


3

The Altair is the first of a category of machines that gave rise to CP/M — you'd need to add more RAM, a disk drive, a serial port and a terminal but adding to the box was standard usage; the Altair is the originator of the S-100 bus. With CP/M you have word processors like WordStar, spreadsheets like Super Calc, databases like dBase, programming ...


3

From the Altair 8800 Theory of Operation Manual & Schematics 1975: The Single Step circuit consists of a dual single shot (IC M) for debounce and the SGL STP flip-flop (R-S type). When the machine is in a stopped mode, depressing the SS switch will set the SGL STP flip-flop. (The machine must be stopped for any of the front panel switches except ...


3

We put a half-meg of memory into an STD bus Z-80 on CP/M 2.0 in the early eighties. It was (IIRC) a hardware + software solution from a company in Ottawa, Canada. The core of the program fit into 32k, and the other 32k was switched in and out. Sorry I don't remember more. I do remember that the system also had a proprietary file system built over the top ...


2

You can find some Intel 8080 CPU tests on this website. These can be run with no OS, just a minimal support framework described below: These binaries should be loaded to memory starting at 0x0100, and at startup, your CPU should jump to 0x0100. You should also put two handlers at addresses 0x0000 and 0x0005: The handler at 0x0000 signals the end of the ...


2

In many cases, you can maximise profit by having one price for many people, and another price for a few - you just have to somehow achieve this. If you have one price, then the number of customers gets less as you increase the price, but the profit per item grows, and there is an optimal point. If you manage to offer a different price point at less ...


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