[FRAM71] Pre-Production Batch

[rprosperi]

(02-07-2015 06:55 PM)Hans Brueggemann Wrote:  In a recent e-mail, Dave Frederickson pointed out to me that it would be nice to be able to access all 512kB of FRAM, by using some sort of bank switching scheme. i find this idea quite intriguing and FRAM71's FPGA still has ample amount of free logic available (as per V.421) to handle such a task. alas... i'm short on ideas of how to implement that to gain maximum use from such a feature. when looking at the used FRAM address space (nibble addresses),
00000-1FFFF is reserved for diagnostic/alternate O/S,
20000-2BFFF is unused,
2C000-2C01F is reserved for Memory Configuration,
2C020-2FFFF is unused,
30000-FFFFF is reserved for the 0..12 configurable Memory Chips.
that gives basically the range 20000-2BFFFF as a possible candidate for bankswitching.
so, what can we do with that? is it worth a try in the light of the amount of FRAM already available?
what's your take on this, valued users?

hans

Dave and I have been discussing this for a while... and it grew out of wondering why the full 512KB wasn't accessible. Clearly FRAM71 has the means to do it, so why doesn't it do so? There had to be a reason, we reasoned. And I guess that lead to your discussion.

I have yet to find anything serious that exceeds FRAM71's current abilities, but also haven't tried yet. Still, I would say that yes, it's worth it. I've never owned any calculator* with which I haven't run into a memory limit, whether doing "serious" work, or just experimenting/playing. Before Clonix/NOV and the CL were made, who would have ever guessed that a 41 could ever need more that 4 modules? Now, 4, 5, or 6 are just the basic OS/system build, before adding-in app roms.

From your notes above, it appears one could create a bank-switched scheme with a 16KB window in the available address space, and while a 32KB window would be more convenient to, for example, swap-in/out ROM images or IRAMs, this is still useful.

Just some feedback to stimulate discussion.

* Notable exception - I've never filled my 50g 2 GB SD card