I was a Zenith computer technician. Nice Heathkit H8, it was fun programing in offset octal keypad than hex. This brings back so many memories. Thanks for the nostalgic video.
I have all of the source code for HDOS, the assembler H8ASM, the BASIC H8BASIC and all of the ancillary modules including the boot ROMs and device drivers for the printer, general serial port, 8 and 5 inch floppies (H-17, H-47) as well as the 10m hard drive, the H-67. Coolest feature of HDOS was a clever file format that added *.REL and *.OVL files to the usual *.COM (aka *.ABS) file extensions for code. This was a way of creating relocatable code that could be located anywhere in RAM no matter the amount of memory. The file header pointed to a table of addresses within the code that would need to be corrected if the program was loaded 2nd or fifth. Like loading the BASIC and the ASSEMBLER at the same time. As you added RAM you could go from 16k to 64k and did not need to reassemble the programs. The overlays allowed normally unused OS apps to be loaded to top of memory only when needed. Far ahead of it's time and the dev is almost unknown. Far smarter than Gates but not as ruthless. Thanks, J.G. Letwin.
I bought one of these at a San Diego swap meet around 1982. It had a minimalist ram card. Was never upgraded. Came with an H19 terminal as well. Bought the combination for a grand total of $30. It was in mint condition. Bought a 300 baud modem from radio shack, it was my first venture into online computer communications with bulletin board systems (BBS). Funny, I didn't need the H8 to use the modem, just the H19 terminal. After a while I wanted to create a better memory card that would accommodate the 8080's full capabilities. So I designed one, used radio shack sourced circuit board decals. It was a lot of work, but I wanted to do as close to 64k as I could using a newer static ram chip (I think 4k each?). (details are foggy from those days). Every payday I would got to the local electronics supplier and buy another ram chip or two. Static ram was not cheap! Dynamic ram was super cheap but was too complex! Got the board etched, drilled, and filled. It was simply a proof of concept for me. I think I ended up with about 16k of memory on it. When I initially tried the thing, it was wonky as hell. Half the data would store, but the other half wouldn't. I'm like wtf... Was in the Navy at the time and on a waiting list for air controllers in training to go live. There were a lot of people ahead of me that had to deploy, so I had a lot of time on my hands. Went into an empty classroom every day and used the whiteboard, along with Intel data books (the really thick ones back then) to understand what I had done wrong. In the end, I had missed a timing issue, of issuing a hardware write to the chip. You just cant send a write command to a chip and expect it to respond immediately. Doesn't work that way. It takes a milli or micro second or two for it to be ready to accept the data. Fixed it by putting two inverters in series with that line to introduce a fake delay. It worked. The stuff we throw out yesterday. Who knew what their value would be today. We never learn.
The serial card available from Heath for the h8 could operate reliably up to 19, 200 baud. It was not unstable when connected to compatible rs232 devices. The instability that you spoke of is based on your setup not the fact that he's card could not handle those speeds correctly.
Thank you for this trip down memory lane. I never owned one but I spent my childhood reading Heathkit and Edmund Scientific catalogs because we were too poor to actually subscribe to paid magazines haha..
No need to turn the system off then back on to do a reset. You simply need to press the RST and 0 keys simultaneously on the front panel. I heard you mention the paper tape reader as an optional peripheral but most people started out with either a single or dual cassette tape recorder system to store and load programs. Ah, the good old days. I still have my H8, my H19 and my dual 100k disk drives - many, many hours spend with those systems back in the day.
The H11 paper tape reader was NOT the most common external storage device. FAR more common was the cassette interface that was integrated on a card that also contained a single serial port designated for the original H9 (upper case only) terminal. The cassette interface ran at 1200 baud, 4 times as fast as the cassette interface for the Altair/Imsai machines. The interface could be operated with a single cassette machine (R/W) or dual machines which greatly simplified operations. The cassette machines sold by Heathkit were General Electric branded. They served the H8 community well until the advent of the floppy drive interface later on. It's also worth noting that the BASIC originally supplied by Heathkit (named "Benton Harbor BASIC" after the headquarters city of the company) was a custom 'dialect' of the language unique to the H8. You had to carefully comb through any source code written for a different machine to eliminate invalid commands or syntax. This problem was eliminated by the eventual adoption of a custom version of the original Microsoft Basic interpreter. This program allowed source code written in the Microsoft dialect to run on any machine that had a version of the interpreter written for it.
The H10 was the paper tape reader while the H11 was a separate computer based on the DEC PDP-11. The H10 is actually quite rare. My electronics class in the early 70's had a PDP-8 computer with a Teletype terminal which did have a paper tape reader attached to it which we would use to load Dartmouth Basic from folded paper tape. I remember that a local university had a PDP-11 with a high speed paper tape reader.
I remember the 2k low loader monitor ROM in the H-17 floppy drive that was copied in hardware into the first 2k of RAM. it came with a 4k SRAM or 8k SRAM board out of the box. If you had at least 16k of SRAM you could load rhe ahead of it's time HDOS operating system.
Nice Heathkit H8, I am considering picking one of these up myself, to learn more about them. Your system seems to have a very bright and clear display. I was wondering when you might be producing another video???
Actually, Heathkit did offer the H8 in fully assembled form for more money - I have a sales brochure for it as well as one of the machines and tons of documentation and software for it. I would be interested to know what the Adrino is doing... is it just acting as a terminal emulator for downloading the files because your Mac terminal mode doesn't have that function or is there more to it? Could I just use a full fledged terminal emulator like Kermit instead?
Hello. I still have my H8 that I built when I was 16. Would you be willing to share your Arduino interface information? I'd love to get my computer operating again. I did restore it and had to replace a few bad caps. Unfortunately I no longer have the H19 terminal.
Exvellent video.Thanks!!
Thank you for this fascinating look into computer history
I was a Zenith computer technician.
Nice Heathkit H8, it was fun programing in offset octal keypad than hex.
This brings back so many memories.
Thanks for the nostalgic video.
I have all of the source code for HDOS, the assembler H8ASM, the BASIC H8BASIC and all of the ancillary modules including the boot ROMs and device drivers for the printer, general serial port, 8 and 5 inch floppies (H-17, H-47) as well as the 10m hard drive, the H-67. Coolest feature of HDOS was a clever file format that added *.REL and *.OVL files to the usual *.COM (aka *.ABS) file extensions for code. This was a way of creating relocatable code that could be located anywhere in RAM no matter the amount of memory. The file header pointed to a table of addresses within the code that would need to be corrected if the program was loaded 2nd or fifth. Like loading the BASIC and the ASSEMBLER at the same time. As you added RAM you could go from 16k to 64k and did not need to reassemble the programs. The overlays allowed normally unused OS apps to be loaded to top of memory only when needed. Far ahead of it's time and the dev is almost unknown. Far smarter than Gates but not as ruthless. Thanks, J.G. Letwin.
I bought one of these at a San Diego swap meet around 1982. It had a minimalist ram card. Was never upgraded. Came with an H19 terminal as well. Bought the combination for a grand total of $30. It was in mint condition. Bought a 300 baud modem from radio shack, it was my first venture into online computer communications with bulletin board systems (BBS). Funny, I didn't need the H8 to use the modem, just the H19 terminal.
After a while I wanted to create a better memory card that would accommodate the 8080's full capabilities. So I designed one, used radio shack sourced circuit board decals. It was a lot of work, but I wanted to do as close to 64k as I could using a newer static ram chip (I think 4k each?). (details are foggy from those days). Every payday I would got to the local electronics supplier and buy another ram chip or two. Static ram was not cheap! Dynamic ram was super cheap but was too complex!
Got the board etched, drilled, and filled. It was simply a proof of concept for me. I think I ended up with about 16k of memory on it. When I initially tried the thing, it was wonky as hell. Half the data would store, but the other half wouldn't. I'm like wtf... Was in the Navy at the time and on a waiting list for air controllers in training to go live. There were a lot of people ahead of me that had to deploy, so I had a lot of time on my hands. Went into an empty classroom every day and used the whiteboard, along with Intel data books (the really thick ones back then) to understand what I had done wrong.
In the end, I had missed a timing issue, of issuing a hardware write to the chip. You just cant send a write command to a chip and expect it to respond immediately. Doesn't work that way. It takes a milli or micro second or two for it to be ready to accept the data. Fixed it by putting two inverters in series with that line to introduce a fake delay. It worked.
The stuff we throw out yesterday. Who knew what their value would be today. We never learn.
The serial card available from Heath for the h8 could operate reliably up to 19, 200 baud. It was not unstable when connected to compatible rs232 devices. The instability that you spoke of is based on your setup not the fact that he's card could not handle those speeds correctly.
Thank you for this trip down memory lane. I never owned one but I spent my childhood reading Heathkit and Edmund Scientific catalogs because we were too poor to actually subscribe to paid magazines haha..
No need to turn the system off then back on to do a reset. You simply need to press the RST and 0 keys simultaneously on the front panel. I heard you mention the paper tape reader as an optional peripheral but most people started out with either a single or dual cassette tape recorder system to store and load programs. Ah, the good old days. I still have my H8, my H19 and my dual 100k disk drives - many, many hours spend with those systems back in the day.
The H11 paper tape reader was NOT the most common external storage device. FAR more common was the cassette interface that was integrated on a card that also contained a single serial port designated for the original H9 (upper case only) terminal. The cassette interface ran at 1200 baud, 4 times as fast as the cassette interface for the Altair/Imsai machines. The interface could be operated with a single cassette machine (R/W) or dual machines which greatly simplified operations. The cassette machines sold by Heathkit were General Electric branded. They served the H8 community well until the advent of the floppy drive interface later on. It's also worth noting that the BASIC originally supplied by Heathkit (named "Benton Harbor BASIC" after the headquarters city of the company) was a custom 'dialect' of the language unique to the H8. You had to carefully comb through any source code written for a different machine to eliminate invalid commands or syntax. This problem was eliminated by the eventual adoption of a custom version of the original Microsoft Basic interpreter. This program allowed source code written in the Microsoft dialect to run on any machine that had a version of the interpreter written for it.
The H10 was the paper tape reader while the H11 was a separate computer based on the DEC PDP-11. The H10 is actually quite rare. My electronics class in the early 70's had a PDP-8 computer with a Teletype terminal which did have a paper tape reader attached to it which we would use to load Dartmouth Basic from folded paper tape. I remember that a local university had a PDP-11 with a high speed paper tape reader.
So clever using the Arduino.
I remember the 2k low loader monitor ROM in the H-17 floppy drive that was copied in hardware into the first 2k of RAM. it came with a 4k SRAM or 8k SRAM board out of the box. If you had at least 16k of SRAM you could load rhe ahead of it's time HDOS operating system.
Very cool. Thanks for showing it to us!
I also would be very interested in details about the Arduino interface.
HDOS from HealthKit was a far better os than MSDOS… source code was available and modifications to the overlays was easy
Would very much tech data on your ARDUINO interface and software.
I had modified the rom os to using hex instead …
Nice Heathkit H8, I am considering picking one of these up myself, to learn more about them. Your system seems to have a very bright and clear display.
I was wondering when you might be producing another video???
We should have a few new videos coming to you within the next few weeks!
@@intergalacticmuseumofcompu6880 Looking forward to it !!!
Still looking forward to seeing a few more videos.. What have you been up to? What is the status of getting an actual museum, up and running?
Actually, Heathkit did offer the H8 in fully assembled form for more money - I have a sales brochure for it as well as one of the machines and tons of documentation and software for it. I would be interested to know what the Adrino is doing... is it just acting as a terminal emulator for downloading the files because your Mac terminal mode doesn't have that function or is there more to it? Could I just use a full fledged terminal emulator like Kermit instead?
Hello. I still have my H8 that I built when I was 16. Would you be willing to share your Arduino interface information? I'd love to get my computer operating again. I did restore it and had to replace a few bad caps. Unfortunately I no longer have the H19 terminal.