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Thread: Honeywell 200 resurrection

  1. #131

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    Great to see this progress! I'll bet you can almost hear the system running now!

    Do you think it will be ready for a cameo spot in the remake of "Billion Dollar Brain"?

  2. #132
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    I can hear it running already actually, but that's just the fans cooling the vintage PSU's.

    The problem with "Billion Dollar Brain" is that the key scene portrays cards being read into a model 223 card reader. Okay, so maybe building a 223 from scratch may be within someone's capabilities, but finding a supply of punched cards could prove more difficult. Anyway, there seems to be a misconception that the H200 was the billion dollar brain in the title, but it clearly wasn't. Apart from being a free-standing small mainframe in its own right the H200 was also used as a satellite machine for far larger ones, which is why it was designed with such versatile peripheral capabilities. The scenes in that film evidently portray such a set-up.

    At least in that film the H200 shown was a real complete machine actually being operated normally. H200 control panels were very photogenic and therefore appeared in other films where there was no evidence of there actually being an H200 computer as well. In the title sequences of that film they did put a lot of bogus stickers on the control panel and even when the real machine was shown it had a prominent HONEYWELL sticker on the control panel where there shouldn't have been one to provide a little extra point of action product placement.

    I'm currently putting together a test circuit to determine the precise operating characteristics of the Honeywell flip-flop ICs that I will be using in the control memory so that I can design the PCBs for it. Sixteen identical PCBs with gold-plated edge connectors will cost a fair bit for my supplier to manufacture, so I need to get the design right. I know the basic logic functions of the ICs but also need to assess the fan-out and line driving capabilities as well as the effect of the feedback capacitors that Honeywell included in their designs. I noticed that in older designs they were included but in later versions of the same boards some were omitted, so there seems to have been some lack of clarity about when they were really needed. Modern digital ICs don't have analogue feedback pins to permit wave-shaping adjustments, so design with them is much simpler, but these ICs were used in circuits on wire-wrapped backplanes with long interconnecting wires and plenty of scope for induced noise.

    So far I have discovered that with an 18MHz clock pulse into a flip-flop switching at 9MHz a 33pf feedback capacitor changes the (sort of) square output pulse into a triangular one because the rise and fall times are slowed down so much. Interesting. No doubt at slower switching speeds that might be useful. I can see why the standard logic boards were described as containing "slow gated buffer amplifiers". Oh well, I'd better get back to the workbench to add the next frequency divider stage. The basic cycle clock rate of the H200 was 4MHz, so I should be using a 16MHz crystal anyway but don't have one handy, not that it matters for now.
    Rob - http://www.honeypi.org.uk
    The Internet is a winch to get your project off the ground ... but always have a parachute handy.

  3. #133

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    Quote Originally Posted by RobS View Post
    The problem with "Billion Dollar Brain" is that the key scene portrays cards being read into a model 223 card reader. Okay, so maybe building a 223 from scratch may be within someone's capabilities, but finding a supply of punched cards could prove more difficult. Anyway, there seems to be a misconception that the H200 was the billion dollar brain in the title, but it clearly wasn't. Apart from being a free-standing small mainframe in its own right the H200 was also used as a satellite machine for far larger ones, which is why it was designed with such versatile peripheral capabilities. The scenes in that film evidently portray such a set-up.
    Yeah, I got that impression watching the scene with Karl Malden. From what I could follow, he was doing little more than printing out a message from a mag tape, possibly after decrypting it - which was probably all local to the H200... not that there was actually a "billion dollar brain" attached to the H200...

  4. #134
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    Quote Originally Posted by durgadas311 View Post
    Yeah, I got that impression watching the scene with Karl Malden. From what I could follow, he was doing little more than printing out a message from a mag tape, possibly after decrypting it - which was probably all local to the H200... not that there was actually a "billion dollar brain" attached to the H200...
    No, I doubt that there was. The film was made with the cooperation of Honeywell and that set was quite possibly a Honeywell data centre with many computers in it.

    I've now added the next flip-flop to halve the frequency again, so I'm now getting nine pulses in two microseconds. It should be eight if I use the correct crystal, but who's counting? Oh yes, I am. I must add a 16MHz crystal to my shopping list. Two microseconds was the cycle time of the main memory and there were eight distinct time slots within each such cycle. Control memory cycled four times faster, so executed a read-write cycle every half microsecond, which is my design target. The logic gates appear to have around a 25 nanosecond propagation delay, so with just 250 nanoseconds per time slot I have to bear that in mind. Those feedback capacitors really slow response times down though. Perhaps I don't need to provide for them in my PCB design at all.
    Rob - http://www.honeypi.org.uk
    The Internet is a winch to get your project off the ground ... but always have a parachute handy.

  5. #135

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    Quote Originally Posted by RobS View Post
    I'm currently putting together a test circuit to determine the precise operating characteristics of the Honeywell flip-flop ICs that I will be using in the control memory so that I can design the PCBs for it. Sixteen identical PCBs with gold-plated edge connectors will cost a fair bit for my supplier to manufacture, so I need to get the design right. I know the basic logic functions of the ICs but also need to assess the fan-out and line driving capabilities as well as the effect of the feedback capacitors that Honeywell included in their designs. I noticed that in older designs they were included but in later versions of the same boards some were omitted, so there seems to have been some lack of clarity about when they were really needed. Modern digital ICs don't have analogue feedback pins to permit wave-shaping adjustments, so design with them is much simpler, but these ICs were used in circuits on wire-wrapped backplanes with long interconnecting wires and plenty of scope for induced noise.
    I'm guessing the parts are RTL/DTL ICs then? I never worked with that technology, but saw some in the Wang 600/700 programmable calculators. I didn't realize you could still get those parts, or is this recycled chips? Anyway, kudos to having the courage to work in that space! I saw some wire-wrap backplanes (newer tech) that used twisted-pair wiring... did Honeywell use any of that to reduce noise?

  6. #136
    Join Date
    Sep 2012
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    Quote Originally Posted by durgadas311 View Post
    I'm guessing the parts are RTL/DTL ICs then? I never worked with that technology, but saw some in the Wang 600/700 programmable calculators. I didn't realize you could still get those parts, or is this recycled chips? Anyway, kudos to having the courage to work in that space! I saw some wire-wrap backplanes (newer tech) that used twisted-pair wiring... did Honeywell use any of that to reduce noise?
    I am using original ICs manufactured around 1971 althought the designs for many of the boards that they are on date from 1969 or earlier, so they were certainly in use in the 1960s. The original transistorised H200 used discrete diode and transistor logic, as is evident from the schematics. The earlier circuits had single ended outputs with pull-up resistors but the later circuits used push-pull transistor output stages. From my tests on the ICs they also appear to have push-pull output stages. I think that they are more advanced than RTL (I have some old RTL ICs which are much more primitive.) but I have no reason to believe that they are TTL, so DTL is the most likely. I suspect that they are basically integrated circuit equivalents of the technology used in the previous discrete diode transistor boards. Those had feedback capacitors and Honeywell appear to have included them in their DTL design as well as external components, all the rest being within the ICs. The flip-flops are relatively sophisticated, being master-slave devices with three pairs of anded input gates and a "recirculate" pin which causes the current state to stay latched during clock pulses although the inputs can still set the flip-flop. This style of flip-flop logic may be the reason why on the H200 control panel you could turn individual bits on but could only turn them off by clearing an entire display line. Hitting the "Clear" button on the left hand side presumably killed the recirculation of the data in the flip-flops. One might assume that the buttons worked in press-on-press-off fashion, but the majority of them didn't. The H200 was designed to be as cheap and easy to build as possible, for which I am grateful.

    The boards in my collection from the 1970's contain in total around 5000 ICs, which should be enough to build the machine. There are only seven main types of IC on them, so I have about a thousand of each of the common types. They each contain two logic gated buffers or one flip-flop, so I actually have around 9000 to 10,000 gated buffers to play with. If I really get short I may be able to add extra diodes to extend the fan-in of some of the gates. I can also add transistors as output boosters to increase fan-out where necessary. I am likely to spend as much time experimenting with the ICs as actually building the machine, but it's all part of the fun for me.

    My test circuit is still sitting here clocking up cycles while I'm typing, so I ought to get back to it. My oscilloscope must be getting bored with tracing it by now.
    Rob - http://www.honeypi.org.uk
    The Internet is a winch to get your project off the ground ... but always have a parachute handy.

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