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2

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 ...


7

(There is a rather complete Wiki-article about) While it is not used as much nowadays, Still widely in use, just not so much with fine electronics. then passing the board over a standing wave of solder. It's rather the edge of a 'solder-fall', but there were various designs over time. How does the stuff know it is supposed to only stick to the ...


3

The PCB is coated with a solder mask. That's usually the green shiny layer on the surface of the PCB. There are openings in the solder mask on places that need solder. So the solder only sticks to exposed copper pads and component legs.


1

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 ...


2

It is my understanding that many microprocessors used dynamic logic. The likes of the 6800,6809 and the 6502 used this. This reference discusses one such technique: https://en.m.wikipedia.org/wiki/Four-phase_logic


2

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 ...


1

There are three ways an attempt to load a tape can fail: The loader reports success, but the data is incorrect. The loader reports failure and does not read correct data. The loader reports failure, but in fact loads the data correctly anyhow. Commodore's tape system does a very good job of preventing failure #1. Unfortunately, it writes two complete ...


11

Many early computers were sold as self-assembly kits Not really. They were only more visible than the 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 (semi-) professional ...


3

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 ...


3

The datassette doesn't have the bias circuit on recording, because on digital data wasn't necessary, and also has sensors that informed if the motor was engaged. Also the power supply was from the computer so no batteries or extra plugs were involved. On the reproducing part a circuit designed to process a digital signal doesn't introduces unnecessary stages ...


23

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 ...


13

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 ...


24

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 ...


18

The Datassette has a digital interface, and since it is not meant to process audio signals at all, it allows directly writing sharp digital magnetic transitions to the tape, using a single monophonic read/write head. The written pulses are always written at same amplitude, so there is no variation between equipment. Also when reading the transitions off the ...


3

I believe the datasette had the ADC built in, so it could then transmit digital signals to the computer. By optimising for digital output, the unit should have been more reliable, compared to a conventional tape player which would have bias settings for a more accurate output of analogue sound data.


3

Although the CDP1802 was implemented as a single chip, a preceding version was implemented as two chips. I don't know exactly how functionality was split, but the architecture would have been very amenable to subdivision into two chips--one of which would hold the 4-bit P and X registers along with the sixteen numbered 16-bit registers and the logic to ...


1

Even without three-state drivers, one could have fairly easily built a computer with an Altair-style front panel by using three-position switches that included a contact for the middle position which would connect the CPU. For the machine to run, the address and data switches would need to be in the middle position to let the CPU drive them. Such a design ...


2

But in any case, doesn't the Altair front panel depend on the ability to do exactly what is described, tri-state the CPU in order to take over as a DMA device? Would that be a significant obstacle to building such a system around the 6502 (at least without having to provide extra logic which would tend to negate the cost advantage of the CPU itself)? ...


8

One thing to note – the 8088 registers are made from dynamic memory cells – they have to be refreshed. This was unexpected (at least to me), Same to me. And I guess to anyone else as well. Ken Shirriff's analysis of the 8086 registers clearly shows that they are not dynamic, but static, using the same inverter loop as the 8080 already did (and essentially ...


-4

How i managed to do it on a "modern" 486 board with integrated IDE: first i needed to disable IDE controller in bios IMPORTANT: for whatever reason this drive only works as secondary slave drive, the other drives are selected on the BIOS as "None" and the actual disk is selected as drive type 2 the drive is a tandon 20mb mfm drive


34

Classic IBM 224 Dictating Unit using a magnabelt, often called a Dictaphone, although that wasa trademark of a different company. Introduced in 1966 and sold in high volume and worldwide, way into the 1970s. Seen here in action. So while being from IBM, it's in no way computer related. They are still a common find. Only complete setups, including the ...


3

[While having a twist in its own, I got a feeling this had be answered already some time ago, in context about the ways to mark bus cycles on 8 bit CPU, but can't find it right now] To start with, the page mentioned compared kind of Apples and Oranges, as it's about Intel 8080 vs. Motorola 68000 (*1). These were complete different CPUs designed at different ...


14

Yes, because it did not provide the necessary connections for wider use AGP had asymmetric bandwidths. It was very much faster in transferring data from the CPU to the graphics card. For transferring data back from the graphics card to the CPU though, it was no faster than a PCI slot. For graphics cards, this is exactly what you need. You typically do not ...


1

It turns out that the price difference was not as large as I thought it was. According to http://www.oocities.org/peterochocki/computers/1980comp/swtp6800.htm the $395 for the SWTPC was in kit form, which means it compares to $430 for the Altair, a rather small price difference. Raffzahn is probably right that the $35 difference is accounted for by the ...


42

I researched this question online fairly thoroughly a while back. I could not find any reference to an AGP device that wasn't a graphics card. It wasn't exhaustive, and absence of proof is not proof of absence, but I strongly suspect no such cards were made. I also think there are technical and economic reasons that make it unlikely. It would have been a ...


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 ...


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 ...


3

The particular printer is an IBM Printer Model 4, aka IBM 4693 / 4694 / 93F0463. It's an impact receipt printer introduced in 1991. The printer has distinctive up-down arrow control buttons on its left front side. Apart from the very distinctive dot-matrix impact sound, these are journal printers that print the same lines on two different rolls. So instead ...


5

The cash register is an IBM 4693 or 4694 and in 1995 it had just been moved from IBM's General Sales Application to Walmart's own internal point of sale system. If it was still running GSA the display would have said "AMT/TEND" or "ENTER AMT/TEND" when the cashier entered the $20.00 tendered instead of whatever it said. Walmart receipts ...


2

To give you a sense of the inter-board spacing in these types of systems, it is useful to consider the main constraints. These include airflow for cooling, the physical space between the connectors on the backplane and component height. The gap for airflow purposes was such that most folk could slide their fingertips between boards, but only at the expense ...


7

It is said to be rack mountable, though the width has been given at 59.5 cm, which is 23.4 inches; I thought a standard equipment rack was 19 inches wide? Not really. It's a bit wider than 49 cm or 19 inches (*1) as shown here: So it's safe to assume that the 59,5 you found might have been a typo. One thing I have not been able to find is a figure for the ...


6

In answering this question, I found that there were multiple generations of 11/780 memory board, and so sizes, capacity, etc., are quite hard to pin down. I still have not found a board larger than 4MB. I did get an answer for physical board size, though not for slot width (board separation). One MS780 memory controller can take 16 memory array boards. ...


2

Not all desiccant bags are create equal. Silica Sand Beads only adsorb moisture and stick to surface. Expanding Polymer bags absorb and can pull moisture into bag in enclosed spaces. check it out. https://www.youtube.com/watch?v=0U6kIsGj9X8&t=5s&ab_channel=SteelCamel


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