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Interested in USB for TURBOchannel (slhci at tc)?


tinkering with a Lattice CPLD break-out board and a Waveshape SL811HS USB board showed success: I was able to interface the SL811HS and TURBOchannel of my DEC 3000/400. Code for "slhci at tc" was easy, as the slhci driver seems mature (and portable) already. The CPLD features a TC interface up to 25 MHz, is capable of I/O transactions and interrupts, and even contains a basic option ROM as required by TC systems' firmware. It is a horribly "flying" lab setup with single wires between all the connectors at the moment (hardly stable of course, but sometimes :)), but I plan to design a "real" TC option module with custom PCB and even bulkhead for myself (and others if interested) which will solve all stability problems I hope.

Do not expect it to be fast, SL811HS is a USB 1.1 controller (12 Mbit/s) and its 8-bit interface is sub-optimal (and errata-prone). I calculated SL811HS peak data rate over an optimal (back-to-back) TURBOchannel to be ~1.25 MB/s for 12.5 MHz TC systems, and ~2.08 MB/s for 25 MHz systems. Actual devices on the bus will show slower results of course.

Is anyone else interested in such a TC-USB option? I could kick-off a hobbyist maker project of professionally made modules (you would get the assembled thing with parts soldered to a PCB, CPLD programmed and bulkhead mounted) then. Costs depend on amount ordered of course, but even for prototype/smallest volume I see it far below USD $100. I will not earn a single cent. Otherwise I will build manually for myself only. So please excuse cross-posting to the three TC-capable platforms (pmax, alpha, vax). It's a NetBSD special right now :)

More info is and will be available here (doc, pics, code, ...):

And the alpha port seems to have really broken bus functions for widths <= 4 (dense vs. sparse TC space etc.). I will also come up with a patch for that soon.

Comments and suggestions welcome!


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