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MZ DA Starter Kit
http://retrobsd.org/viewtopic.php?f=12&t=39868
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Author:  BenLaskowski [ Sun Jul 15, 2018 11:54 pm ]
Post subject:  MZ DA Starter Kit

Hello everyone!

I purchased an MZ DA started kit with stacked DRAM a couple weeks ago to get familiar with some of Microchip's higher-end parts and because I thought it would be educational to try to get LiteBSD to use its internal DRAM and SDHC peripheral.

So far, I've added an SD breakout board to an SPI port (just to get things running) and have gotten the system to boot with a few minimal code changes. My working code is here: https://github.com/BenLaskowski/LiteBSD/tree/mzda-starter-kit

My rough plan is to use the onboard DRAM for something, then work with the SDHC. I'm torn with how to use the DRAM. Should I edit the linker script and initialization code to use exclusively the DRAM - thus reducing the need for swap - OR should I create a new driver (called dram, perhaps) that can be the block device that LiteBSD wants for swap?

I notice that the default config uses a 32 MB swap partition, and the onboard DRAM is 32 MB, so it seems like the second option is a natural fit. Something like cc would still swap a bunch, but copies between internal memories would be a lot faster than accessing the SD card, and there would be no SD lifing concerns. I presume this way is also preferable since we'd still get zero wait state execution from SRAM.

Thoughts?

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