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Old 16 August 2012, 20:20   #133
Join Date: Jun 2010
Location: out in the wild
Posts: 1,133
Thanks for those values. I have optimized chipmem access further, and I have found that I'm flushing the caches too often. The mass-produced board has a slightly different wiring for the logic chips, so I can precisely identify if I need to flush caches or not (to experts: Function code lines were pre-decoded in the other CPLD, and are now wired directly to the memory controller). This has already helped performance on the ACA620, and it'll bring the ACA1220 higher as well.

Further, I have decided to not use a canned oscillator, but a PLL to generate the main frequency. The PLL is kind-of programmable with SMD resistors (bridges). This will make overclocking easier, but I won't get tired to emphasize that overclocking is done at your own risk. Memory design is overclocking-friendly, but the CPU is rated 16MHz by Motorola, so that's the highest frequency I will guarantee

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