Dr. Scott M. Baker Builds a New Storage Card for the Heathkit H8 — Utilizing Seventies Bubble Reminiscence



Engineer Dr. Scott M. Baker is as soon as once more upgrading his traditional Heathkit H8 microcomputer, however this time it is actually extra of a side-grade — including classic bubble reminiscence for non-volatile storage, rather than a contemporary CompactFlash card interface.

“Bubble reminiscence was a expertise of the Seventies, maybe enduring a barely longer life cycle within the industrial equipment area, the place equipment vibration was notably problematic for storage gadgets like floppy disks or onerous disks,” Baker explains.

“Bubble reminiscence makes use of particular magnetic patterns deposited on a substrate resembling garnet, to have the ability to migrate magnetic “bubbles” in a loop configuration. You’ll be able to rotate the bubble you’re across the loop and the duplicate it for studying, or you’ll be able to swap in a unique bubble for writing. Magnetic bubble reminiscence is a non-volatile reminiscence and can protect its contents on power-off.”

A classic Heathkit H8 microcomputer now boasts period-appropriate bubble reminiscence — with slightly marble-run demo of the expertise’s performance. (📹: Dr. Scott M. Baker)

To utilize bubble reminiscence expertise, Baker designed a brand new add-on card for his kit-form Heathkit H8 microcomputer — a tool launched again in 1977 and designed to run Digital’s CP/M working system on an Intel 8080A processor with a static RAM (SRAM) card providing a meager by trendy requirements 4kB of reminiscence. Baker’s newly-designed bubble reminiscence board, although, is not designed to exchange the system’s RAM however as a substitute provide non-volatile storage so applications and knowledge aren’t misplaced on energy off — changing the paper tape or cassette storage an unique H8 was seemingly to make use of.

“Craig’s SBC-85 design offered me with virtually the whole lot I wanted to start out with,” Baker explains, referring to an earlier deep-dive bubble reminiscence venture by Craig Andrews which served as inspiration for Baker’s personal design. “There’s the schematic of his SBC-85 board itself, in addition to 8085 meeting code for studying and writing sectors and exercising different instructions on the bubble reminiscence controller. My duties had been the next: interface the bubble reminiscence controller to the H8 Bus; write a storage driver for HDOS, so the bubble reminiscence might be used as a disk; add help to Douglas Miller’s Newmon monitor for the H8, in order that bubble reminiscence might be booted instantly. That is a few weekend’s value of tinkering…”

Baker’s Heathkit has been having fun with one thing of an overhaul over the previous 12 months, beginning with the creation of a customized add-on board granting the microcomputer the facility of speech. This was adopted by a way of interfacing a contemporary Raspberry Pi with the machine, then a customized reminiscence board design — which crammed 16MB, and doubtlessly as much as 32MB, of RAM right into a design constructed for a 4kB board. And now, it boasts 1Mb (128kB) of bubble reminiscence storage — utilizing period-appropriate {hardware}, not like trendy CompactFlash-based different storage boards.

Extra info on the venture is obtainable on Baker’s web site, although the schematics, {hardware} design recordsdata, and software program haven’t been made obtainable publicly whereas the newest board revision undergoes ultimate verification.

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