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Thread: Silly Address/Data LED front panels on 80s machines.. or are they?

  1. #1
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    Default Silly Address/Data LED front panels on 80s machines.. or are they?

    I have a few examples of machines that included the Address/Data LEDs on the front panel that indicated the status of the CPU bus. Most infamously the Altair 8800 included one out of necessity. It was initially the only display device in the system. They led to 'Kill the Bit' and other novel uses. But mostly later non-practical versions were an ode to the large computer displays depicted in movies like War Games. Big-Iron had to have Big-Incandescent indicators.

    But oddly, they were sometimes 'a thing' in the 80s. I supposed it made computers look more expensive than they actually were if they have lots of 'blink'n lights'. I have a PCjr add-on upper-deck module that has address and data lines for the ISA bus. No amount of clarity a good engineer posses will cause him or her to 'see the code' Matrix-style in the noise..... or so I thought!

    I've been working on a FPGA project I plan on announcing at VCF-MW. The FPGA is sitting on the ISA bus and is a bit pin constrained. I didn't have enough extra pins to add taps for a logic analyzer and the two on-board LEDs were getting a bit limiting. So I added a neopixel strip to add another 88 RGB LEDs to my debug display! The obvious first choice was to add the address LEDs (lower 10 in blue/green) and the ISA data lines (red).

    What I didn't count on was how mesmerizing the 'dancing LEDs' were when playing wave-table music through a GUS. Here is a short video of the Descent menu music playing while filming my bus monitor!

    https://youtu.be/39o-VkpNY4o
    "Good engineers keep thick authoritative books on their shelf. Not for their own reference, but to throw at people who ask stupid questions; hoping a small fragment of knowledge will osmotically transfer with each cranial impact." - Me

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    That's pretty slick. It also kind of reminds me of how you used to be able to set an AM radio next to a TRS-80 and get a pretty good idea of what it was up to based on the noises you'd get out of it.

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    I went from an MITS 8800 to a LED-less Integrand chassis. Didn't make any difference in utility.

    Blinkenlights were out of fashion in the 70s. Consider, for example, the CDC 6600 (1964):



    Not so much as a power LED. The only operator-accessible switches was the deadstart panel--a short program loaded into PP0:



    Just below the two displays on the operator's console, there was a concealed button that would best be described as a reset button.

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    Quote Originally Posted by Chuck(G) View Post
    Blinkenlights were out of fashion in the 70s.
    While I love your insight on a great many things, the post was more about finding a specific example of blinkin bus lights actually being visually useful; eg. dancing to wave table music. But thanks for the CDC pics!
    "Good engineers keep thick authoritative books on their shelf. Not for their own reference, but to throw at people who ask stupid questions; hoping a small fragment of knowledge will osmotically transfer with each cranial impact." - Me

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    I made a cartridge for the Commodore 64 that has LEDs on each of the address and data lines (as well as some other status lines). After building it all, I was quite disappointed that mostly all it does is show most of the lights half dimmed. They go off or bright once in a while, but it's really disappointingly uninteresting (I assume) because even at 1MHz, it's too fast to see anything.

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    I can at least imagine some circumstances where it might be vaguely useful if you had one in a machine that had a well-defined memory map, IE, you might be able to get a feeling of how much time the machine is spending in ROM verses RAM based on the relative brightness of the LEDs... But, yeah, without a facility for single-stepping it doesn't seem like you could get much more than a "vibe" out of it.

  7. #7

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    Nö mention of the CM-2?

    I hope nobody is in favour of omitting the indicators from PLC racks. That's a major pain in the backside.
    https://www.machinedesign.com/sites/...PLC%20Rack.jpg

  8. #8

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    The Poly 88 was claimed to be one of the first S-100 computers with only two switches, a power and reset, on the case. It had a boot ROM that included a monitor to load programs and debug.
    Dwight

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    The Sphere-1 is the first micro I can think of that made a big selling point of not having a front panel, but it and the SWTPC 6800 went on sale (for all practical purposes) at almost the same time as the Poly-88. Beat it by two or three months, maybe? Was there something about the 6800 that made it less amenable to front panels?

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    Surely, the MCM/70 had to precede all of those other LED-less micros:



    And then, how about those MPU boards that used 7-segment or numeric displays, like the KIM-1? No dancing LEDs there.



    IBM made a big deal of lotsa lamps on their operator's consoles. Look up the System 360/195 for yourself.

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