A little personal milestone
This is no big deal to most of you, but today I entered a simple front panel program solo for the first time (on the HP 1000 thanks to Mike L.'s excellent teaching last weekend). Hey you, David G.! This means I'll have more confidence the next time I try your similar program on the PDP-8.
On Sun, Jun 18, 2017 at 12:15:53AM -0400, Evan Koblentz via vcf-midatlantic wrote:
Hey you, David G.! This means I'll have more confidence the next time I try your similar program on the PDP-8.
Once you get comfortable with one the others are just variants on the theme, at least for the smaller machines. Never got to play with any of the machines with truly impressive panels. At VCF I checked the pdp-8 and the program was still in it and ran. If you need the instructions again or any of the other docents desire I can send the info again. Hopefully we can get it doing something more interesting in the fall.
Once you get comfortable with one the others are just variants on the theme, at least for the smaller machines.
I am starting to understand that. For some reason I found it easier on the HP than on the 8 when you showed me.
At VCF I checked the pdp-8 and the program was still in it and ran. If you need the instructions again
I have the instructions you made for entering the program (I will take a fresh look at them to see if they make more sense to me now) but I'm unclear about how to restart the program still in it from before.
Hopefully we can get it doing something more interesting in the fall.
Agreed! IIRC your advice was to run FOCAL through the teletype once we locate the misplaced connector card.
On Sun, Jun 18, 2017 at 04:35:05PM -0400, Evan Koblentz via vcf-midatlantic wrote:
I have the instructions you made for entering the program (I will take a fresh look at them to see if they make more sense to me now) but I'm unclear about how to restart the program still in it from before.
Set the address switches to 100 (octal) then hit load address switch then start switch. Halt and single step switches must be off. I had start address of 0 in the original write up. That will work for initial start up but 100 is better for restart. 100 will work for initial startup also, Before powering off the computer hit the halt switch to stop the program running. If you turn off pdp-8 with it running it will corrupt memory. I shouldn't do that but as the voltage falls the logic stops working correctly before the low voltage circuit halts the processor. FYI: There is one front panel light (memory bufffer 3) that is flaky. It may light when it shouldn't or flicker.
Hopefully we can get it doing something more interesting in the fall.
Agreed! IIRC your advice was to run FOCAL through the teletype once we locate the misplaced connector card.
I think we also have to fix the teltype. I don't think it was working. Focal is a resonable program to demo though there are other reasonable programs. Just the * prompt probably won't be that exciting so need to pick/write Focal program to run. We also have the plotter though I need to make an interface for it. The PDP-8 has an A/D converter though currently disabled. Probably we need to discuss at some point more on the trade space of demo closer to historical usage of that machine / period usage / of sufficient interest to visitors. Doesn't have to be one demo either though switching demos adds complications.
Set the address switches to 100 (octal)
It's like a light bulb has illuminated and is reflecting off my bald head! I've long been able to do the long-form math (on paper) for octal/hex, but now I suddenly "get" what someone means by "set the address switches to 100 (octal). Off/off/on -- off/off/off -- off/off/off. Better late than never, huh?
On Sun, 18 Jun 2017, Evan Koblentz via vcf-midatlantic wrote:
Set the address switches to 100 (octal)
It's like a light bulb has illuminated and is reflecting off my bald head! I've long been able to do the long-form math (on paper) for octal/hex, but now I suddenly "get" what someone means by "set the address switches to 100 (octal). Off/off/on -- off/off/off -- off/off/off. Better late than never, huh?
It's all just ones and zeroes. :-) All you really need to know is this: 8 4 2 1 Hex Dec Oct ------------------------------- 0 0 0 0 0 0 0 0 0 0 1 1 1 1 0 0 1 0 2 2 2 0 0 1 1 3 3 3 0 1 0 0 4 4 4 0 1 0 1 5 5 5 0 1 1 0 6 6 6 0 1 1 1 7 7 7 1 0 0 0 8 8 10 1 0 0 1 9 9 11 1 0 1 0 A 10 12 1 0 1 1 B 11 13 1 1 0 0 C 12 14 1 1 0 1 D 13 15 1 1 1 0 E 14 16 1 1 1 1 F 15 17 Want to convert a hex number to binary? Just decode each hex digit (I know, it's not really a digit) to its 4-bit binary equivalent, left to right: e.g. B5 hex => 10110101 binary Want to convert that to an octal number? Just group the bits by threes, starting with the Least Significant Bits (LSB), then insert the octal equivalent for each group of three: 10 110 101 => 265 octal I was going to go over this with you last weekend, but didn't get around to it. :-) Mike Loewen mloewen@cpumagic.scol.pa.us Old Technology http://q7.neurotica.com/Oldtech/
All you really need to know is this:
8 4 2 1 Hex Dec Oct ------------------------------- 0 0 0 0 0 0 0 0 0 0 1 1 1 1 0 0 1 0 2 2 2 0 0 1 1 3 3 3 0 1 0 0 4 4 4 0 1 0 1 5 5 5 0 1 1 0 6 6 6 0 1 1 1 7 7 7 1 0 0 0 8 8 10 1 0 0 1 9 9 11 1 0 1 0 A 10 12 1 0 1 1 B 11 13 1 1 0 0 C 12 14 1 1 0 1 D 13 15 1 1 1 0 E 14 16 1 1 1 1 F 15 17
Want to convert a hex number to binary? Just decode each hex digit (I know, it's not really a digit) to its 4-bit binary equivalent, left to right:
e.g. B5 hex => 10110101 binary
Want to convert that to an octal number? Just group the bits by threes, starting with the Least Significant Bits (LSB), then insert the octal equivalent for each group of three:
10 110 101 => 265 octal
That's the problem. These things are usually taught in big charts of numbers. It is a question of learning styles. I stare at these charts and my eyes glaze over! Can't do it. But when you put me in front of the panel and you showed me how there's a 4s place, 2s place, and 1s place, that made perfect sense. Just flip the switches that add up to the instruction for each set. I can do that.
On Sun, 18 Jun 2017, Evan Koblentz via vcf-midatlantic wrote:
That's the problem. These things are usually taught in big charts of numbers. It is a question of learning styles. I stare at these charts and my eyes glaze over! Can't do it. But when you put me in front of the panel and you showed me how there's a 4s place, 2s place, and 1s place, that made perfect sense. Just flip the switches that add up to the instruction for each set. I can do that.
Understood. As long as you know your powers of 2, you're golden. Mike Loewen mloewen@cpumagic.scol.pa.us Old Technology http://q7.neurotica.com/Oldtech/
participants (3)
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David Gesswein -
Evan Koblentz -
Mike Loewen