Intel MCS 4/40

This Web page last updated Nov 6 2024. It's part of a number of repair and restoration Web pages I have which are linked from this linked Web page My Intel Multibus Web pages have a home at this Web link.- Herb Johnson

Introduction: the Intel MCS 4/40 and UPP, 4040 computers

I acquired at a hamfest in the 2000's, an Intel MCS Intellec 4/40 system; also an Intel Universal PROM Programmer or UPP. In late 2012 I acquired an empty UPP chassis. These are Intel 4040 processor based systems for development from the early 1970's. Intel intially developed the 4004 processor, followed by the 8008, and then later the 4040 and the 8080 became available about the same time. This page shows the Intellec 4/40 I have. In the course of March 2014, I got the Intellec 4/40 to run under its ROM serial monitor.

In Oct 2023 I acquired another intellec 4/40, from the estate of the original owner Lawrence Hale. It's incomplete but largely intact.

Another Web page shows the Intel UPP's I have, formerly they were on this Web page.. The UPP includes an Intel 4040 based controller, but (I believe) does not have ANY board plug-compatible with the intellec 4/40.

Here's a bit of discussion I wrote about Intel's time before the 8080. Also, here's a chapter from Intel's MCS-40 User's Manual on the Intellec 4/40.

Additional Intel 4040-based items were acquired by me in 2006. It included a set of 4040 Prolog-brand cards and Prolog brand docs for the 4004 and 4040. Prolog developed the STDbus, an industrial standard for decades used for microcomputer based control and data systems.

The Intellec 4/40 and Prolog model 900 PROM programmer were exhibited in 2014 at Vintage Computer Festival - East 9.1.

PS: Closely related to the MCS 4/40 and UPP, was the later Intel Intellec 8 and 8 mod 80 or 8/80 systems. I have fragments of those products, which I detail on other Web pages.

- Herb Johnson

Intel mcs intellec 4/40

Here's the mcs intellec 4/40, viewed from the front panel.
Here's a description of the front panel exerpted from a MSC-4 Development System document
Kyle Owen provided a description of the ROM monitor commands
In Dec 2022 I received images of the MCS-40 Reference Card which I processed and PDF'ed.

Images of the cards and chassis:

The 4/40, showing off the cards. These are not Multibus cards, not S-100 cards, but an unnamed connection scheme of 100-pin cards.

Photo of the 4/40 chassis from above. The three cards on the left are CPU (leftmost), mem control, RAM. The card alone on the right is the PROM programmer card.
the rear of the chassis, various conectors
the bottom of the chassis, note the foldout stand
For details of the hinged top and front panel, look over here

Photo of the 4/40 CPU card with local RAM and ROM M000276.chips dated 1975
Closeup of the 4/40 ROMs and CPU.
Photo of the 4/40 memory control card 0000073. date 1973-74
Photo of the 4/40 RAM card 05-0042.Board date 1972, chips date 1975. 4K bytes of 2102A-4's.
Photo of the 4/40 PROM programmer card 0000090. board dated 1973, chips 1975

Serial number: My intellec 4/40 is serial number 147. In Jan 2023 I scooted around the Web to look for other serial numbers. They were all below mine! Even serial numbers for intellect 8 and 80 were below 500; the largest was an intellec 8 number 417 in Australia.

In 2023, Sid and I speculated on how many 4/40 systems were built, and if they were mass produced. Sid suggested that some of the assembly was not professional-looking, so he speculated they were built by hand. Web search in Jan 2023 did not find a serial number higher than mine (147) and that suggests a small number. the general chassis is likely OEM (small run or stock product from a cabinet company). The 8/80 in a similar cabinet, is likely small-run too, serial numbers in the few hundreds. Intel's systems took off when (or as) Multibus was created.- Herb Feb 2023

chassis color: "Did some research on the paint color of the MDS888 and figured out it was almost exactly the same as Sherwin Williams Polane-T Nitro Blue. This just happened to be the same blue that I had my paint vendor use on a product in the 90s. Got a few oz from him along with catalyst and did some touch up work. Perfect match." - Roger Arrick, from rogerarrick.com. Web search shows this was used by tektronix: "Blue, Nitro; Polyurethane, low sheen; Sherwin Williams Polane T F63L17; tek # 252-0266-00" . Other products of the era referenced this color and paint.

Comparison of intellec 4 card's connector pinouts

Here's a pinout of the CPU card; and here's a pinout of the Memory Control card. and here's a pinout of the RAM memory card. The "memory control module" shares control with the CPU board of the memory; it also ties to the "control and display" front panel, and to the rest of the "bus" to the memory and I/O boards. The Control Module provides access to both program and data memory, which is otherwise separate in the 4040 architecture. I don't pretend to know the 4040 architecture; remember that it and the 4004 preceeded the 8008 and 8080 architectures.

A "PROM Programmer" for 4702A PROMS is also part of the standard system. Other modules as documented are optional and include "data storage", "input/output", and a few others. A rough check of these modules - RAM memory, PROM memory, Data Storage, I/O - suggests they have some common "bus" lines, drawn from the CPU module, Control module, and the panel.

Follow this link, for a comparison of the intellec 4/40 and intellec 8/80 bus signals.

intellec 4/40 ROM dump

Aug 2013: Kyle Owen contacted me to show me the ROM dumps from his 4/40 system. But 1) the data was inverted from proper 4040 object code; and 2) one of his four 1702A's was all FF's - blank or dead!. He encouraged me to read off my EPROMS. Check out my Web page on Kyle's work and mine on the 4/40 EPROMs. - Herb

Aug 2013:My colleague Dwight Elvey came across Kyle's discussion of his work and mine with our 4 Mod 40 systems, as Dwight calls them. Here's some notes from Dwight about his Intel Corp. experiences with the 4 mod 40.

Feb- Mar 2014: Paul Robson contacts me and offers to disassemble my ROMs and Kyle's. See his results on my 4/40 ROM page. With further discussion with Kyle about his 4/40 work, Kyle encourages me to get my 4/40 running.

Intellec 4/40 runs!

In March 2014, I had discussions with Kyle Owen about the operation of his 4/40 system, and he encouraged me to power it up and see what it can do. The power supplies are simple linear supplies, he reminds me, and not likely to fail. I open up the Intellec 4/40 and "float" the cards by pulling them out of the backplane but kept in the chassis. I run the power supply with a Variac at 30 volts AC (20% voltage) for half an hour -more than enough time to reform the electrolytics. I monitor the power supplies (5V, -12, +12, -10, +80!) and see they are all regulating at 100v with full voltage. And, the front panel (which gets 5V) is lit and displaying. So, I power down and wait tens of minutes to insert the cards. Meanwhile I do a quick ohms check on the card's 5-volt supply lines, to be sure there's no shorts. I see none, and plug the cards in, and slowing bring up the complete systems.

Sure enough, it starts to run! In the photo, I've single-stepped part of the ROM program. The next thing, is to hook up a current-loop terminal to the rear Cinch-Jones connector. That's the 8-pin rectangular connector to the left of the lable on the back. The D-connectors further to the left, are to the bus for I/O. The D-connectors to the right, hook up to the I/O ports on the internal boards.

Here's a document exerpt for the operation of the front panel. read the notes on the ROM disassembly for some idea of how to run the ROM monitor.

interface for serial monitor

After obtaining and wiring up a Cinch-Jones connector, I worked on an interface to a serial "terminal", that is a serial port on an old laptop running MS-DOS and a terminal program. The interface was modeled on Kyle Owen's work, plus work on a TTL-to-RS232 interface for another vintage project. Kyle used optoisolators to convert the current loops on the Intel side, to voltage levels on the terminal side. His interface was to an Arduino, so he could convert the "logic" and baud rates in software. I chose to use a laptop with RS-232 levels.

It took a few days to get the "logic" right. Fairly soon, I was able to recieve the "command prompt" from the Intellec, a [CRLF][.] string at 1200 baud. But the INtellec kept sending [CRLF][.*] continuously. Was there a problem with the ROM? or hardware on the Intellec? It eventually occurred to me, to check the serial input current loop to the Intellec. I found that when I shorted the loop, the monitor stopped sending; when I opened it, it sent continuously. Apparently it interpreted the open-loop as a character and sent the * to reject it.

I struggled with trying to design an optoisolator circuit that normally "closed" the loop, until a character was transmitted from the terminal. The inactive RS-232 line is negative several volts; active bits drive the line positive for several volts. I eventually determined I needed a PNP transistor to provide sufficient current drive to the opto's LED diode, to force the phototransistor to conduct and "close" the loop; opening the loop as the terminal sends bits in each character. Here's the interface circuit for both Intellec transmit and recieve. The 8-pin Cinch connnector pins are drawn on the upper left; pins 1 and 2 are the transmit current loop, 3 and 4 the receive current loop. The INtellec internal circuits are shown to the left. On the right are the two optoisolators, plus the PNP transistor which drives the receive opto-diode. Here's a fuzzy photo of the breadboarded circuit. The circuit on the terminal side was powered by three AA cells at about 4 volts, at full charge 4.5 volts. RDX, TDX and GND are the RS-232 terminal (laptop) connections on a DB-9.

here's a screen shot of a RAM dump, prompted by the D command from the terminal. The Intellec panel shows a "blink" when characters are sent or recieved; it's a software UART bit-banged to recieve or send each character from the CPU board. The front panel during monitor operation is shown on this linked photo.

4/40, mechanical details

Hinge of front panel.
Hinge of front panel.
Hinge of front panel.
Hinge of front panel.

Hinge of top cover.
Hinge of top cover.
Hinge of top cover.

In Oct 2023, I was asked about details of the plexiglass clips that secure either side of the chassis cover.
clip photo 1
clip photo 2
clip photo 3
clip photo 4 with dimensions

Intellec 4/40 software and support from Intel

In Feb 2023 I received some 4004 4040 intellec software documents from Sid Jones, a 4/40 owner. This sample of cover letters reveals and confirms that Intel distributed a two-pass paper tape assembler and a paper tape editor for the 4040 system. Details forthcoming as I recieve further documents. - Herb

SIM-04 ROM based assembler

In 2018 Dwight Elvey initiated an online discussion in this vintage computing Web forum, about a 4004 design he developed from a project overseen by Gary Kildall as a professor at the Naval College. The discussion progressed in 2020, to a discussion of a set of Intel intellec SIM-04 (4004 coded) ROMs he dumped and disassembled. Later he obtained similar ROM images to verify. These four 1702 ROMS, marked A0740 through A0743, contained an Intel 4004 native assembler. "It was written by Tom Pittman, in the early Intel days" on an Intel SIM-04, a 4004 development board, such as Dwight owns and still operates. (Other Intel native assemblers ran from RAM or ROM in the Intel intellect 4/40 systems.) Archives of Intel 4004 4040 documents include an assembler manual. Dwight added the ROM images to his Github site for his 4004 project.

At this Github link, Dwight describes the four ROMs as an assembler and archived the ROM binaries. "With some help from Dave Roberts, I fixed an error in my [SIM-04] simulator and was able to successfully run Tom's assembler. Instructions [for the assembler] can be had from bitsavers.org in the "MCS4 user Manual", in Appendix F. "Dwight also archived a set of PROMs for programming a 1702A with an additional card for the SIM-04. Read his notes there for some details, other details are below.

In Feb 2023, I had email conversations with Dwight Elvey, Sid Jones (an intellec 4/40 owner), Jon Hales (works with vintage intel at a UK museum), Al Kossow. Dwight brought up the 4004 assembler ROMs at Sid's request.

During 2023-24 I had discussions with Dwight Elvey about disassembly of the four ROMs. Contrary to his GitHub notes, he believes he has a good set of those ROMS and their code. But it's hard to interpret the code as Tom Pittman used a few tricks to jam the assembler into four 1702 ROMs for 1Kbyte of total 4004 code space. One trick from the era is using a JCN jump-never two-byte instruction, as a "SKIP" to hide a one byte instruction as the JCN address byte. This cannot be explained briefly. Other coding tricks by Pittman are harder to figure out. There's also some variance, in how Intel assemblers (and Dwight's disassembler) processed JCN condition code syntax. Additionally, as in any disassembly, it's hard to know what is code and what is data.

OK: for those impatient, here's some actual code results.

Dwight Elvey produced a disassembly; however he uses a FORTH-like syntax which is unfamilar to modern programmers. Here's Dwight's FORTH-syntax disassembly listing. Dwight's correspondents about the 4004 assembler, found those results unsatisfactory. As it happened, I could modify an 8085 disassembler into a 4004 disassembler. My disassembler (entirely derived from code for 8085 disassembly by Bill Beech) is table driven so it's a matter of changing tables and some decision logic. Also, my disassembler produces Intel-syntax 4004 source.

Here's my resulting Intel-compatible 4004 disassembly. Also, from Dwight's correspondence, here's a commented Intel-format disassembly of the first ROM image by Dave Roberts. The ROM images, are archived on Dwight Elvey's github page, and also at bitsavers.org's MCS4 components archive. The disassemblies are not archived at those locations.

In all three disassemblies I provide, the "SKIP" instruction is disassembled as such. It's very likely intended in the first two instances of the ROM code. In the third instance, it's unclear. If you wish to assemble the code without implementing the SKIP, change it to "DB 10H ;SKIP" for your 4004 assembler. (I'll refer you to my 4004 assembler later.)

In Nov 2024, Dwight Elvey described how the SIM-04 ROM-based assembler is to be used. He's run it on a simulated SIM-04.

"The assembler is [on 1702 ROMs marked by Intel as] A0740, A0741, A0742 and A0743. It is intended to be connected from the SIM4-01 (or -02,-03) to an ASR-33 Teletype, with paper tape punch and reader. It needs to have flow control [of the reader and punch] as described in the MCS-4 User's Manual Feb 1973, Appendix D, as found on bitsavers.org Intel components page.

"The assembler is a two pass assembler. The first pass result is put on the punch tape. The resulting tape is then run through the second pass, to punch the ROM image punch tape. The tape data format [later called "BNPF format] is what Intel was using for mask ROMs and such, as shown in the MCS-4 User's Manual [section XIII, "MCS-4 PROM Programming System"]. The result of the second pass can be used on the SIM4-01 with MP7-03 [board] to program 1702A, using the prom set A0450, A0451 and A0453. Note that for 1702 ( non-A ) programming, PROM A0542 is used in place of A0543 . The code listing for the 1702A programming prom set is in the User Manual, Appendix I ["MCS-4 Programming Example"]. I'm hoping to recover A0542 from a PROM I have. - Dwight Elvey"

Dwight added a description for use of the Pittman 4004 assembler ROMs followed by the 1702A programming ROMS:

"Changing the EPROMs for the assembler to the [ROMs for the 1702a} programmer code. The assembler runs on the SIM4-01 without the programmer card. Here are the steps.

Place the A074x EPROMs on the SIM4.
Connect it to power and the ASR33.
Feed the source tape into the ASR33.
When pass 1 is done, take the tape created above with the output of pass 1 to the reader.
When the pass 2 tape is done remove the A074x EPROMs and replace them with the A045x EPROMs..
Add the Programmer and programmer power ( 60 volts dc ).
Then use the pass 2 tape as the source for the programming.. - Dwight

I'll update this information as time permits. Possibly I'll move it to its own Web page. - Herb, Nov 6 2024

Intel Universal PROM Programmer (UPP)

Details of my Intel UPP's are now on this linked Web page.

According to the Intel Data Catalog for 1977, the Universal PROM Programmer is an Intellec system peripheral capable of programming and verifying a number of Intel PROMS, the Intel 8748 Microcomputer (processor chip) and the Intel 8755 PROM and I/O chip. It can hold two "personality cards" to program chips in the two PROM sockets on the front panel. The UPP-101 model has a 16 pin and 24-pin pair of PROM sockets; the UPP-102 has two 24-pin PROM sockets on the front panel. The Intel document describing the hardware is the "Intel Universal PROM Programmer Reference Manual" #9800122 or #9800133; I read the 9800133 version.

Data and control for the UPP, is performed over a 25-line "interconnection cable". The cable runs from the control board in the UPP, to an Intel Development System, running either ISIS-II or a paper-tape based Intellec System Monitor to run the "Universal PROM Mapper" program.

My cursory read of both the UPP Reference Manual and the 4/MOD-40 manual, tells me that boards between the two systems are incompatible, even though they both use a 100-pin connector and similar board dimensions.

my Intel UPP #1 and #2

Here's a complete UPP or Universal PROM Programmer. It uses a 4040 processor, and was designed to be used with a terminal or with the intellec systems. There's apparently a control card and two "personality modules" for different PROM families.

Details of my Intel UPP's are on this linked Web page.

Intel Intellec 8, 8/80 systems; comparison to 4-bit Intellec

the Intel Intellec 8 and Intellec 8/80 chassis, looks like the MCS 4 and 4/40 chassis. Of course they use different processors. From some inspection, these have a limited "bus" structure (see the pinouts for my MCS-4/40 cards). It's not likely most cards for the 4-bit system won't work with the 8-bit system; there may be exceptions. I don't have a complete 8-bit Intellec; it's useful to list what I have on this Web page in the meantime.

intellec 4/40 vs 8/80: pretty close

In March 2023, I've changed my opinion about the relationship between the Intellec 4/40 bus and the Intellec 8/80 bus. They are both busses, and they are similar to each other. There's some possibility of cards for one, running in the other. BUT check every board signal and check the bus-slot signals *carefully*. Slots on either system are dedicated in various ways to specific signals and of course, DC voltages.

In Jan 2013, my colleage Kyle Owen, who owned in 2013 both an intellec 4/40 and 8/80, gave me his opinions. this is a photo of Kyle's CPU board with ROMs. In Jan 2013, Kyle looked over his Intel docs and his systems and said: "I have gone through both systems and can confirm that there would be no compatibility between an 8/80 and 4/40. Yes, they use the same 100-pin card and dimensions, but no, the bus structure is completely different. The 4/40 opted for "universal" sockets with exceptions for several of the "stock" cards like CPU, memory controller, etc., whereas the 8/80 opted for duplicate single-purpose slots. I have the [Intel] information for this." He agrees that neither systems are Multibus, a visual inspection makes that obvious. He describes the motherboards as "passive cross-wired connecting assemblies".

Intel describes their 4-bit and 8-bit Intellec systems and boards, in their 1975 "Intel Data Catalog". Thanks to that reference and discussion from Craig Andrews in Dec 2021, I took time to transcribe the board-level descriptions from that manual. In 2021 I found a copy on the deramp.com Web site in their component/Intel/memory components archive. HOwever, apparently I did not study these hard enough.

By early 2023, Craig Andrews developed his versions of the intellec 8/80 boards and backplanes. In his accounts, he suggests some compatibity between intellec RAM and ROM cards for either system. Or at least, replica cards of his creation. So: I compared the intellec 8/80 RAM slot signals, with the intellec 4/40 RAM slot signals. Here's a document that lists each of the bus RAM-slot signals side by side.

What that and other documents suggest, is that many critical intellec signals, like address and data and some signaling, are the same for an Intel intellec RAM card for either the 4-bit 4/40 system or the 8-bit 8/80 systems. And an examination of the backplanes for the 8/80 system, show higher-order addresses are preset per RAM or ROM slot (4 of each are on the 8-bit backplane). There's other differences, notibly DC voltages, and other signals from various other parts of the bus.

I suggest, confusion on this matter of "bus structure", is a post-1980 bias for widespread use of "universal busses", where every slot is wired identically to every other slot. From that view, the per-slot differences on the intellec systems, bias a conclusion based on that non-uniformity. But in the 1970's and earlier era, many computers and digital controllers had a variety of backplanes with degrees of uniformity, or none.

my Intel Intellec protoboard

Here's an Intel protoboard for the Intellec bus chassis. I obtained this in Nov 2013. Here's the back of the board. It's a 100-pin card but not like a S-100 bus card. The Intellec "bus" (not really a parallel bus but a collection of sometimes common lines) uses the same S-100 bus 50-pin by two edge connector (.125 inch spaced pins). None of the "bus" pins are predefined on this board. Th intel board is 8 inches wide, not ten like S-100. The Intel board is almost 6 inches tall, not 5-1/2" like the S-100. But one could cut down a generic S-100 protoboard for use.

Intel 8080 ROM monitors, boards

Here's some results of dumping and disassembling some PROMS with early Intel 8080 monitor code.

Coming up: Intel 8080 CPU board for MCS-80. - Herb

Copyright © 2024 Herb Johnson