@16:15 The four 24-pin packages symbolized (upside down) 'NS8260N' are the Signetics 8260 bit-slice adders-that is the arithmetic heart of the CPU. Each one is a four-bit adder with carry look-ahead. Later revs of this board used a multi-function ALU like the Fairchild 9341 or the TI 74181. That reduced the part count considerably but, because the Nova's instruction set was designed around the early minimal hardware, the later revs of these models didn't use all the functions those bit-slice ALUs provided.
@ForgottenMachines
Жыл бұрын
David, thanks for this comment...this is VERY helpful, and I really appreciate it! Please, keep comments like this coming on this channel...your feedback is exactly why I share these videos. Thank you!!!
@jimbates6227
2 жыл бұрын
The board ejector levers can be forced and the result will be their breaking out of the corner of the board. The board covers serve two purposes. (1) They protect the components, and (2) they reduce electronic interference between boards. The nylon standoffs on bottom of the first CPU board may have been there to insure the board doesn't sag too close to the power supply below the board. If a boards are flexed or sag, there would risk breaking the traces on the board. The handle on the front end of the board also helps reduce sagging. I believe the two CPUs would reside on the bottom two slots in the chassis. Right above the power supply. The 800 series was updated when I joined DG in 1977. I didn't ever see too many. My DG time started with Nova 3, and the first Eclipse series S100/S200/C300. The 800 series was mostly 7400-series TTL. I had schematics of these systems on paper and then microfiche. Of course, that was 45 years ago. The Comm Basic I/O Board isn't fully populated so that means it's missing some functions. Maybe it's missing a parallel port, or a serial port, etc. The connections to peripherals are done through wiring attached to the backplane.
@ForgottenMachines
2 жыл бұрын
Wow...thank you for such a thorough and helpful reply! I'm certain you are correct on all accounts, except for one minor detail, that being the power supply is not underneath any of the boards. The power supplies are adjacent to the stack of boards, (or behind them, depending on your perspective). So no sagging of the boards could ever make them come closer to the power supplies. However, everything else you say about why things are designed and used the way they are clearly are absolutely correct! And of course you are, you worked at DG back in the day! VERY cool! How do we get in more direct contact with you? Could you please email me at entrex480.blogspot.com/p/contact.html ? I'd really love to hear from you there, thank you!!
@youreale
2 жыл бұрын
Man, this channel is a gem. I'm in.
@bruceguttman3516
2 жыл бұрын
YLI watermark on the board is Youngblood Laminates Inc. and they made the FR4 material that is the base of the board.
@ForgottenMachines
2 жыл бұрын
Wow, thanks for this knowledge. I LOVE it when viewers give me detailed knowledge like this!!! Did you work in this industry? I'd love to hear more about how you know these details so well...and thank you again!!!
@jaut-76
Жыл бұрын
The circuitry missing on the basic IO controller could be related to interfacing to a later tape reader.
@karlramberg
5 жыл бұрын
Date code on io board chips are (19)80 and 81 so much later than on the cpu board. Most date codes on cpu are 71 and 72
@ForgottenMachines
5 жыл бұрын
karl ramberg thank you so much for pointing that out. That makes me glad that I took the time to record all the chip close-ups, so others can notice things I miss, just like this!
@chucklengyel6882
2 ай бұрын
Another forgotten machine: Jacquard J100 computer,(AM Jacqurd systems) which used boards the same size as the DG Nova, same board ejector handles, 2 of the s100 style gold plated connectors, and it had these thin aluminum rails across the top and bottom of the boards to keep them straight, there was a CPU board with 4 bit slice processor, A memory board, an I'/o controller card for the 8" floppy drive (pertec), and also to connect to the Pertec hard drive. 12" monochrome screen. I believe it was a knock off of the DG Nova.
@ForgottenMachines
2 ай бұрын
Wow...how did you know that I have one of these to eventually reverse-engineer? Kinda spooky that you just "knew" that. I haven't told anyone! Thanks for the comment, we'll get to that for sure!
@chucklengyel6882
2 ай бұрын
@@ForgottenMachines Great! I have Schematics for all the boards, and a J100 manual, I can PDf if needed for you.
@ForgottenMachines
2 ай бұрын
@@chucklengyel6882 Chuck, thank you so much, yes, we would REALLY appreciate that! You can contact me directly at entrex480.blogspot.com/p/contact.html Thank you again!!!
@chucklengyel6882
Ай бұрын
@@ForgottenMachines Hi, Check your Email, I sent you bunch of PDF's
@dosgos
Жыл бұрын
You want to avoid touching any gold contacts in "general" as that can cause a not-insignificant possibility of failure. Regarding contact with the rest of the board, rubber gloves might not be great for ESD and I don't know what best practice would be for these older boards.
@ForgottenMachines
Жыл бұрын
I appreciate this insight, good thoughts. And I promise *not* to use rubber gloves with these.
@dosgos
Жыл бұрын
@@ForgottenMachines I just don't know best practices for gloves with older computer hardware. The pros on CuriousMarc that restore NASA Apollo electronics seem to go with and without various types of gloves on different videos; I'm not sure how they are grounding. Andreas Spiess uses some fancy white gloves which I have seen in Swiss (and maybe some Japanese factories but can't remember). But I think he said his hands were injured so I'm not sure if the gloves are just for visuals.
@ForgottenMachines
Жыл бұрын
@@dosgos Again, great suggestions. But for now, if nothing more than for my own comfort and convenience, I'll be going "gloveless". And we'll see what happens!
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