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I want to fit a TF536 accelerator card into Commodore CDTV case, which is a challenge from the perspective of available space.

MC68000 CPU

TF

I know there is a relocator board project available, but it still doesn't fit the case. The only way I could possibly make it work is by mounting the accelerator card underneath the motherboard. This would however require an extension wires from 68000 socket of around 3-4 inches (7.5-10cm). Is it even possible to create such extension, and does it make sense? Will I mess up the timings or other parameters of the CPU due to delay (wire length vs traces)?

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  • \$\begingroup\$ My guess: these old computers run at quite slow (for today) speeds and don't need very much attention paid to timing. 3-4 inches will be fine. \$\endgroup\$ – user253751 Jun 25 '20 at 17:19
  • \$\begingroup\$ Would it have a low enough profile if you removed the 68000 socket and wired the TF536 directly to the motherboard? \$\endgroup\$ – Bruce Abbott Jun 25 '20 at 20:33
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As the designer of the TF536... most of the 68030 signals are buffered at the 68000 slot so a relocator isnt going to cause an issue... unless the delays are > 5ns or cause voltages to drop significantly

To fit in the CDTV the CPU needs to be soldered directly to the TF536

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You are talking about adding 0.5 nanosecond of delay. With the slow edges, that should be still fine.

You also are talking about adding 100+ nanoHenries of inductance; I use 25nanoHenry/inch as rule of thumb.

To survie that, add 0.1uF across VDD/GND pairs that power the 68030. You must install these capacitors right at the DIP pins

And clock lines could use 220 ohms in series, to dampen overshoots, in either direction.

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The ground pin has to handle all the fast IN/OUT currents. So make the Ground extension be a wide piece of braid, or a dozen stranded wires all in parallel.

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