HP 21MX/F and OS choices (was Lookee what I just got!)

Thanks for the HP-IPL/OS plugs Jay, Here is the fastest known method to bootstrap something useful on any HP1000 series CPU, be that a 2114 with 4K of core up to a 2117F with maximum memory: First off you need to identify your loader ROM's, there are up to 4 of them on a 21MX processor. Core memory machines of course do not use loader roms, you toggle the loader code directly into memory. Hopefully you will have either the 264x terminal loader, or (better, but less common) the paper tape loader. Some documentation claims that the paper tape loader was standard on all E-series machines. Not true, that was written by Engineering before Marketroids started talking with customers. If you don't have the loader rom's you want, no big problem they are available from list members. Ok, next look at what I/O boards you have. The paper tape reader can be used with: Microcircuit I/F GND TRUE I/O + TRUE I/O +8 bit duplex register +16 bit duplex register And several other less common interface boards as well. The 264x 'terminal' boot rom can be used with the super-common BACI board, but it cannot be used with any 12521-series serial interface boards. Now you should have some combination of loader rom and interface board that will talk to each other. Maybe you have no peripherals for your box, frankly that's not a problem. How the machine boots, the EASY way... The simplest bootable software is stored in HP's "ABS" format. This is a series of 8-bit bytes that holds an absolute binary program with memory address, block length, and checksum data. If your booting through the paper tape loader the HP will request a byte with a hardware strobe and wait for an 'ack' signal, read and process the byte, and either request another byte or halt with an error or success code in the S-register. Bytes will be read until the end of the ABS file is reached, or there is an address or checksum error. So the paper tape loader wants a string of 8-bit bytes, using a simple request-acknowledge protocol. The hardware signal DEVICE_COMMAND asserted requests a byte, setting the DEVICE_FLAG signal on the I/O board acknowledges the request, clearing the device command signal until another byte is requested. A simple hack could tie a TTL-level parallel I/O board to a PC's printer port, or a simple microcontroller can emulate a paper tape reader using an EPROM, flash, EEPROM, etc. Booting ABS files from an 8-bit parallel data source is exceedingly fast. It is in fact the single fastest way to load large ABS images, and you can stuff an O/S into memory faster than HP's own disk drives (given a fast source of bytes to read). If you happen to have the 264x loader and BACI interface combo you have a much simpler hardware job, but the loading process is a little more complex. Your still going to need to send a series of 8-bit bytes, but this time over a RS-232 interface. The 264x loader rom sets up the BACI board, then transmits an escape, then a lower case 'e'. This escape sequence tells an HP terminal to begin an 8-bit read of an ABS image stored on those little micro-cassette tapes. But the BACI board is a bit of a beast, there are lots of wires that need to be jumpered correctly in the I/O hood, and the board even has the ability to stall the CPU based on an external signal line. Exactly how this is all configured in an actual HP installation is slightly unclear to me at this time, however it is possible to send RS-232 data into the board slowly without any hardware handshaking. Normally 264x terminals use the handshaking lines, and the loader rom does set some control bits that suggest the booting process expects this to take place. But if the BACI board has been 'strapped' for a basic 3-line RS-232 interface without any handshaking you can listen for the escape-e and then start sending data in the serial format that's set by the I/O board jumpers (in the I/O hood, not on the board!). Pace the serial data so you don't overrun the CPU, and you will eventually halt at the end of the ABS file. This serial method is slow, and at some point someone needs to really poke around inside the code and the BACI interface manuals and figure out exactly what interface strapping and handshaking was used by HP when the loaded field diags and other software using this cute little tape drives (that almost never work anymore, until you fix the rollers and find that good media is unobtainium). With that work done, it may be practical to boot your HP over a serial port at a reasonable speed, but loading a large ABS file this way can take a very long time (as things are). I generally don't recommend the serial boot method due to its poor performance. Then again, I think its nothing to throw together a PIC and some I2C eeprom and build little paper tape reader and punch emulators, and I can burn copies of any loader rom you wish. All that aside, one of my HP's boots from a custom loader rom and an 8-gig IDE drive using a custom controller (so I clearly prefer the hardware solution, build your own peripheral devices). All the others have the ability to boot from an emulated tape reader. One can also boot from CS/80 disks, another has a 7960E. Ok, that's ~how~ to get these things up and running, now the hard part. What to run? If you have less than 8K words of memory: I recommend OCTAPUS-C. Stripped down IPL kernels exist for 4K machines, but its not very practical with less than 8K. IF you have 8K words only: I recommend HPBASIC. This is the 1968 stand-alone interpreter. Has very simple I/O requirements, and its possible to rebuild HP BASIC for non-standard I/O configurations. It supports a 'TTY' console, as well as a high speed paper tape reader, punch, and a printer. Requires a 12521-series console interface (HS TERM), does not support a BACI (well, yes, it will, when patched and run from virtual memory under IPL on a 21MX machine). If you have a 21MX machine. I recommend IPL (HP-IPL/OS). It was designed to bootstrap HP's lacking original peripherals, and its quite powerful. Its a (threaded) interpreter, a compiler, and has an assembler as well. Ideal for blinking lights and reverse engineering device drivers and undocumented I/O boards, etc. It supports all HP1000 CPU's up to, but not including the A-series. Modular and extensible, its even got file systems for disk and mag tape, even F-series floating point extensions, 12555 point-plot graphics via DCPC transfers, etc, etc. Or, you can run RTE, etc. Personally, I've never had the chance to run RTE, TSB, or any of the multi-user time share systems. The only reason I don't recommend these is due to my own lack of knowledge and experience. I 'cut my teeth' on HP's by pulling them out of scrap heaps and bootstrapping them with switches and lights. I've usually found HP1000's in automated test setups, and virtually never is 'data center' applications, so I tend to see these machines as being computers for Engineers. But clearly a lot of people had very different exposures to these machines, and see them through very different eyes. My high school had a PDP-8E that ran a 4-user stand-alone BASIC booted from paper tape, not some dual CPU HP rig!