Mac128, thanks for the insightful article. The for lazy among us (no doubt there are many), here is the relevant paragraph from that article:

Levco has made their system completely compatible with the new Apple file system. Stas Lewak (who was giving the demo) tested the robustness of the new Apple hierarchical file system by copying a folder which had a copy of itself recurusively. He was able to have over 200 levels of folders! ...any changes to the Apple file system would not affect their drive because the system uses the Apple file system. They only wrote drivers to talk to their disk. He said it would be senseless to write a new file system from scratch when the existing one is supported and compatible with the rest of the Macintosh software.

Click to expand...

I agree that it is interesting about the part of about drive-specific drivers. And again, that means that even if we were to follow that Dr. Dobb's article and build MacSCSI, how could we expect to find a "compatible" hard drive that would work with the driver they include?

Next, I am assuming their use of "new Apple file system" actually means "Hierarchical File System" (HFS). If so, that would imply compliance with the 128k ROMs, rather than the 64k ROMs. :-/ It is also interesting to note that Apple introduced HFS in September 1985, and this visit to Levco was made on October 6th, 1985.

But again, this is talking about a LEVCO product I've never seen. I see a memory upgrade board on EBAY right now, made by LEVCO. But through the years, I've not seen the LEVCO 20MB internal hard drive spoken of in that article.