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Glenn’s Computer Museum

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Figure 1: Label of the K4 Bombing Computer
Figure 3: Top of the K4 Bombing Computer4
Figure 5: Side of the K4 Bombing Computer
Figure 7: Side of the K4 Bombing Computer Closeup
Figure 9: Side of the K4 Bombing Computer Closeup
Figure 11: Side of the K4 Bombing Computer Closeup
Figure 13: Early version of K4
Figure 2: Front of the K4 Bombing Computer
Figure 4: Bottom of the K4 Bombing Computer
Figure 6: Side of the K4 Bombing Computer Closeup
Figure 8: Side of the K4 Bombing Computer Closeup
Figure 10: Side of the K4 Bombing Computer Closeup
Figure 12: Early version of K4

K4 Bombing Computer

Here is one of my favorite devices: a “K-4” bombing computer. It’s a favorite because:

--It is old (current device has 1954 markings)

--It computes using electric-mechanical analog mechanisms

--It is very complicated, likely impossible to us to reverse engineer

--It is for the military

--It is very unknown!

About the unknown... I can find almost nothing about this device. The closest are two pictures of an earlier device shown in Pictures 12 and 13, as referenced in https://usautoindustryworldwartwo.com/harris-seybold-potter.htm. These pictures show something much more primative than our device, but abviously there is some resemblence. Maybe this is a prototpe and never used, but its high serial number

Figure 1: Boeing 707 PB-20 Autopilot Top
Figure 3: Boeing 707 PB-20 Autopilot Sample Cards Top
Figure 5: Boeing 707 PB-20 Autopilot Bottom
Figure 2: Boeing 707 PB-20 Autopilot Panel
Figure 4: Boeing 707 PB-20 Autopilot Sample Cards Bottom
Figure 6: Boeing 707 PB-20 Autopilot Back

Bendix PB-20 (Boeing 707 Autopilot)

This is the autopilot used on the first major commercial jet aircraft: the Boeing 707. It was also used on the many models and derivatives of the 707 (such as the Boeing 720) and the many derivative military versions: the Boeing E-3, C-137, KC-135, the Northrup Grumman E-6 and E-8, and others. A derivative of the PB-20 was also used in the first major English-developed jet passenger plane, the Vicors VC-10.

As is generally true with most aviation electronics, once qualified, they live a long time. Our unit, as shown in Figure 2, was last repaired in 10/1990, almost 32 years since the design first flew commercially. Its serial number of 9101 also hints at long life.

Due to the high altitude, the fast speed, and the sweepback wings of the 707 vs. earlier piston-driven planes, the 707 autopilot had to deal with new challenges vs. eatlier types of autopilots. However, since the first commercial flight of the 707 was in late 1958 so this device features primitive 1950's technology including no tubes and very few transistors.

Figure 1 is the looking down at the PB-20. The tube-like shapes near the bottome are not tubes but rather are relays. Otherwise, the logic is contained on about 30 sepeparate plug-in cards. Both sides of selected card examples are shown in Figures 3 and 4.

The bottom view (Figure 5) is a rats-nest of wiring, with the external I/O attached to three 58-pin ports, as also show in Figure 6.

I have flown on a 707 and if I could have seen the ad-hoc physical structure and wiring of its PB-20, I might have had second thoughts. It's hard to imagine that the primitive technology and assembly style shown in Figures 3, 4, and 5 could be "life-critical."

This document discusses some details of the PB-20 design (called "PB20" in this doc).

Figure 1: Ford Mark I Dummy Director Label
Figure 3: Ford Mark I Dummy Director Open Box
Figure 5: Ford Mark I Dummy Director Closeup
Figure 7: Ford Mark I Dummy Director Closeup
Figure 9: Ford Mark I Dummy Director Closeup
Figure 11: Ford Mark I Dummy Direct Closeupr
Figure 13: Ford Mark I Dummy Direct Open Box
Figure 2: Ford Mark I Dummy Director Box
Figure 4: Ford Mark I Dummy Director Panel
Figure 6: Ford Mark I Dummy Director Top
Figure 8: Ford Mark I Dummy Director Closeup
Figure 10: Ford Mark I Dummy Director Top
Figure 12: Ford Mark I Dummy Direct

Ford Mark 1 Dummy Director

Figure 1:
Figure 3:
Figure 5:
Figure 7:
Figure 2:
Figure 4:
Figure 6:

EAI 180 Analog Computer

I truly love analog computers! And, my site has lots of them including the specialized military devices. If you want to know more about analog computers (including their history), how they work, or why they are still useful, I highly recommend the book sitting on the slide-out tray of connectors: "Analog Computing: 2nd edition" Bernd Ulmann. See this reference manual.

Figure 1: B-29 Fire Control Computer Front
Figure 3: B-29 Fire Control Computer Label
Figure 2: B-29 Fire Control Computer Back
Figure 4: B-29 Fire Control Computer Case

B-29 Fire Control computer #2

OK, I know, I know! I already have one of these wonderful fire-control computers! But, since a B-29 had five of these (one for each sighting location, all tuned slightly different), it seems only right that the my museum has several. And, I just can't resist this great 1940-ish technology.

Figure 1: CDC 5601 Front Panel
Figure 3: CDC 5601 Back Panel
Figure 5: CDC 5601 Card
Figure 7: CDC 5601 Power
Figure 2: CDC 5601
Figure 4: CDC 5601 Top
Figure 6: CDC 5601 Power

CDC 5601 Minicomputer

Here’s a “modern” (last maintenance on our device is dated 1977’s, that’s late for our collection) mini-computer from CDC (Control Data Corporation), one of the early leaders in computers.

In particular, ours is labelled as an “input/output controller”, released by the “Aerospace Division” of CDC. Bitsavers has pictures that look just like ours as well as the hardware reference manual, which identifies the 5601 as a “16-bit processor.”

These devices were used in military-type control applications such as identified in this description of an Army “Tactical Fire Direction System” that used several the 5601 instances as well as other members of the 5601 family.

It turns out that the internal design is very similar to some computers I worked on at IBM in the 1970's! It uses a microprogramming control approach which “executes” very simple microinstructions that typically could be used to “emulate” a more normal instruction set. This microprogramming approach was very common on processors of that era, including, of course, the IBM System/360 family and other IBM processors of the 1970s. According to the reference manual, loading a register takes 2.0 us (microsecond) and an register-register add takes 1.3 us. This about 6,000 times slower than the tiny embedded controller that I am working on at this moment.

The 32-bit microinstructions (“nanocode”) were stored in a writable “control-store” memory (I’m using terms more familiar to IBM) that had a 80-ns access time. Each microinstruction could perform up to four operations: ALU, memory, I/O, and choose the next microinstruction location. Again, this is very similar to how many computers of the 1960’s and 1970’s were designed.

We seem to have only the processor itself, not the memory cards.

The two power supplies (on the underside of the processor card area) each produce 56 amps of 5V. That is a lot!

Figure 1: Front of the Sperry Ballast Computer
Figure 3: Card from Sperry Ballast Computer
Figure 2: Top of the Sperry Ballast Computer
Figure 4: Label of the Sperry Ballast Computer

Sperry Ballast Computer

Here is a "ballast computer" from a submarine.

Figure 1: IBM Harvest Tape Cartridge Front
Figure 3: IBM Harvest Tape
Figure 2: IBM Harvest TapeCartridge Back
Figure 4: Picture from NSA Site

IBM Harvest Tape Cartridge

Figure 1: IBM 3890 Control Panel

IBM 3890 Control Panel

Figure 1: B-52 Rear Turret control
Figure 3: Special Weapon Relay
Figure 5: Bomb Relase Mechanism
Figure 7: AWB2 nuckear Weapone Controller
Figure 9: IBM 1403 Printer Chain
Figure 11: Unknown Analog Computer Component
Figure 2: IBM 1800 Computer Banner
Figure 4: Special Weapon Relay
Figure 6: Bomb Relase Mechanism
Figure 8: IBM 1403 Printer Chain
Figure 10: Unknown Analog Computer Component

Various New Items