🇺🇦 haxadecimal 🚫👑2d ago

Does the world need a new single-board computer design with an MC68060 CPU?
I'm thinking about 4GB of DDR3 DRAM, one serial port, one M.2 slot for an NVMe SSD, and one Ethernet port (probably 1Gbps). Not intended to be software-compatible with any existing board or system.

Same question, but various 32-bit RISC processors? MC88110? Am29000/Am29050 (pin compatible)? Intel 80960KA/KB/MC/XA? TI TMS34020?
#retrocomputing

Show threadI love this, so I1d ago
@brouhaha I’m still seriously thinking about building a FPGA ‘040 Classic Mac board that takes “modern” DDR3 RAM, USB keyboard, NVMe SSD, etc. and hopefully can be clocked well above what a 68k could ever achieve.
Show threadI love this, so I1d ago
@brouhaha but maybe I need a different approach for a V1 board - BYO real ‘040 and use a much smaller FPGA that pretends to be the memory (backed by DDR3 RAM) and emulates all the IO
Show thread🇺🇦 haxadecimal 🚫👑1d ago
@jpm
That's what I'm doing. The actual CPUs, just new mem and I/O. Still takes a not-emtotely-trivally-sized FPGA for interfacing to large-ish DDR3 (I really want 4 GiB) and PCIe. An Artix-7 comes close, but my limit the DDR3 size to 1 or 2 GiB.
Show threadI love this, so I1d ago
@brouhaha the bigger pin-count A7 parts can definitely support a single standard DIMM. 434-pin can just but not leave much else. 676 definitely more comfortable.
Show thread🇺🇦 haxadecimal 🚫👑1d ago
@jpm
I only want 32-bit wide (or 40-bit incl. ECC), so I was thinking four or five soldered-down x8 parts, though that is much more expensive than a DIMM or SO-DIMM. Maybe a 64-bit DIMM or SO-DIMM is OK, and just terminate the excess data lines?
For 4Gibytes, it looks like rank of 2 is required, because 8Gibit DDR3 parts (1Gi *8) are dual-die.
I'm nervous because I don't have signal integrity tools to check my layout.
Show thread🇺🇦 haxadecimal 🚫👑
@jpm
I think an XC7A100 or 200 in a 484 BGA with 32-bit DDR3 would leave me over 200 GPIO, which is in the range I want. There's a big price jump for the 676 package from Chinese suppliers (e.g. LCSC).
I'm considering doing a test board first with 2MiB of async SRAM (four 512Ki*8) instead of the DDR3.
Mar 27 at 10:24pmWeb
Show threadI love this, so I1d ago
@brouhaha yeah if you go for 32 bits of hard-wired DDR3 you can get away with a 484, but BYO DDR3 stick definitely has an appeal. The DDR3 clock domain is like an order of magnitude faster than a 32-bit ‘040, so you can probably get away with physical reads and writes being 64-bit from translated 32-bit logical reads and writes.