Heathkit H8 Part 4: 16 Megabytes of RAM in a Heathkit H8 Vintage Computer

Here I make a 16 megabyte RAM board for my Heathkit H8 8-bit computer. The H8 typically shipped with 4K or 8K of RAM, and 64K was a popular upgrade, sometimes requiring multiple boards. There were a few 64K boards back in the day, but to my knowledge nobody has ever made an 8 Megabyte board! Whatever would you even use that much memory for. In this case, I build and used two 8MB boards to add a total of 16MB of memory and used this to create 8 Ramdisks of approximate size 2MB each. The board allows either AS6C4008 512KB RAM chips or 39SF040 Flash chips to be used. The RAM contents are lost at power off (unless battery backup is used). The flash chips are persistent, but much more inconvenient to write. With these boards I also demonstrate the SEBHC Z80 board, and even try the Ramdisks on the original Heathkit 2 MHz 8080 board. You can boot from the Ramdisks. You can image copy one Ramdisk to another. Schematics, gerbers, drivers, etc., are available on my github repo. For more electronics and vintage computer videos, please see www.smbaker.com/

[@edgeeffect]

In this era 16 KILObytes was "massive" ... 16 Meg is simply absurd!!! I Love it.
What a gorgeous machine... I know nothing of this... I'll have to find out more.

[@wa4aos]

Really enjoying your H8 work. That was my first system in the 70's and I still use one of my H8's for various jobs, mainly for fun. Have you played with CPM and a Z80 on your H8? HDOS worked fairly decent but CPM was great; shame gates had IBM shelve it.

[@DAVIDGREGORYKERR]

A ZILOG Z800 and 4x8MB boards would have made for a 16 megabyte PC

[@TooMuchMiddle]

Another fantastic video, Scott. I have to ask, when you were starting out in electronics, that you'd be able to do such rapid prototyping?

[@smbakeryt]

Never in a million years. My first (non-protoboard) PCB was made by laying down tape on a copper board, etching it in a tank, and drilling each and every hole. Every trace was routed by hand. It was single-sided, with no solder mask, and difficult to solder as it was not plated. There were occasional dropouts in the traces that had to be bridged. It was probably a couple of DIP ICs and a handful of components, with a few dozen traces. Then again, I was able to make it in an evening without having to wait half a week for it to be flown in by jet aircraft from the other side of the planet.

[@vanhetgoor]

Interesting, but a Heathkit H8 Computer with 16 Megabytes of memory is a bit overkill, if you would gather all programmes ever made for the Heathkit Computer and store those in the Flash memory. I think you end up with space left vacant. Wouldn't it be a nice idea to add button cel batteries, so that all programmes ever made will be stored in the computer till the end of times or till all batteries fail. (whatever comes first)