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Home » RBC Forums » General Discussion » CB030, A 68030 SBC for hobbyists
CB030, A 68030 SBC for hobbyists [message #6931] Sat, 18 January 2020 09:44 Go to previous message
plasmo is currently offline  plasmo
Messages: 916
Registered: March 2017
Location: New Mexico, USA
Senior Member
Having spent 2 years in the Z80 world, I'm returning to the 68K. Currently I'm working on a 68030 SBC, CB030, named after Cecil B. who is really enthusiastic about Tiny030 and want one even with all the jumpers. Unfortunately Tiny030 design is marginal and not producible so I redesigned it and added additional features specifically for Cecil.

I want CB030 to be simple, economical and build-able by hobbyists. For 68030 these are difficult requirements because 68030 is inherently not economical, simple nor easily assembled by hobbyists. However, it may be possible to meet these challenging requirements with a couple design compromises. The compromises are using a modest surface mount CPLD as the glue logic and using inexpensive commercial SIMM 72 as memory. Great deal of expensive and complex logic can be reduced with an economical CPLD; with vertical SIMM memory stick, the pc board shrink to the economical 100mm x 100mm size; the rest of components are all thru-hole technology so assembly become manageable. The one difficult-to-assemble CPLD is designed to be assembled and programmed first and the partially assembled pc board sold for about $15-20 so the end users can source their own components and finish assembling the board.

Here are features of CB030:
* Low cost 25MHz 68030
* 72-pin SIMM 16/64/128 meg DRAM
* CPLD glue logic
* 8-bit 512K boot EPROM
* 68681 DUART
* 44-pin IDE interface
* 8-bit I/O expansion connector
* 100mm X 100mm pc board
* CP/M68K ready


The 512K EPROM contains a simple monitor and CP/M68K BIOS/CCP/BDOS as well as few basic CP/M68K system files, enough to format new CF disk and transfer files from PC to CF using KERMIT. CP/M68K is a place holder operating system, what I hope for is a modern OS for CB030, but that's beyond my ability right now. Perhaps the low cost, hobbyist-friendly 68030 SBC can attract the software talents for more suitable operating systems.

CB030 is currently in rev0 prototype. It is functional, but there are several mistakes that'll require a new board revision. Of particular note is the DiskOnModule shown in the attached picture. The design calls for a CF disk, but because the connector layout was inadvertently mirrored which happens to match the mirrored pin assignment of DOM, the rev0 board uses DOM instead of CF disk for mass storage. Preliminary information:
https://www.retrobrewcomputers.org/doku.php?id=builderpages: plasmo:cb030spec

Bill
 
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