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PostPosted: Sat Jul 02, 2016 10:15 pm 
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CF has the advantage that it's already parallel and operates at 5V, which might (maybe) be enough to offset its cost premium.

(SD/eMMC will at least require voltage generation, translation, and benefits from external parallel-to-serial conversion)


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PostPosted: Sun Jul 03, 2016 11:36 am 
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lidnariq wrote:
CF has the advantage that it's already parallel and operates at 5V, which might (maybe) be enough to offset its cost premium.

And the disadvantage that it's not really used anymore.


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PostPosted: Sun Jul 03, 2016 11:52 am 
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That only matters if you expect the end user to need to add a CF card, not for manufacture. I'm pretty certain we're not talking about flashcarts.


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PostPosted: Sun Jul 03, 2016 12:09 pm 
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Is there a surface-mount flash memory with a parallel ATA interface that you had in mind? Because if surface-mount mass storage is all eMMC nowadays, you'd need to buy a CF card and mount it in the cartridge. Though I imagine eMMC could be made to work as a DSP source with a CPLD acting as a buffer, with the actual chip clocked by master clock.

But either way, loading most code and data from storage would take up a lot of WRAM in the $7E2000-$7FFFFF area, unless the cart has extra RAM (as on the FDS or SNES CD system cart). And you'd still need either a ROM or an MCU to boot the thing.


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PostPosted: Sun Jul 03, 2016 12:34 pm 
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tepples wrote:
Is there a surface-mount flash memory with a parallel ATA interface that you had in mind?
Disassemble CF card, desolder connector, solder resulting two-sided board in. Needs a funny footprint, but whatever.

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Because if surface-mount mass storage is all eMMC nowadays, you'd need to buy a CF card and mount it in the cartridge. Though I imagine eMMC could be made to work as a DSP source with a CPLD acting as a buffer, with the actual chip clocked by master clock.
eMMC only comes in fine pitch BGA, which is about as hostile to DIY as possible while still technically being doable.

You're going to have a connector of some sort to use bulk commodity memory, or else you're going to be using a known-good-die NAND flash, and as I said, you're going to need voltage translation unless you're using CF.

You can still buy new CF. The prices are not higher enough than SD to make it the wrong choice unless you already have to add voltage translation and programmable logic. Instances where the end user has to buy CF is explicitly out of scope.


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PostPosted: Sun Jul 03, 2016 2:07 pm 
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tepples wrote:
But either way, loading most code and data from storage would take up a lot of WRAM in the $7E2000-$7FFFFF area, unless the cart has extra RAM (as on the FDS or SNES CD system cart). And you'd still need either a ROM or an MCU to boot the thing.

Why are you talking about using flash instead of ROM? I just assumed you were all discussing MSU1. I see no reason to have code or random-access data behind a bulk storage interface when you can have as much as 95 Mbits directly accessible to the CPU without even getting creative...


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PostPosted: Sun Jul 03, 2016 2:34 pm 
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For the same reason some NES homebrew games have switched from battery-backed SRAM to a flash memory that can be programmed in circuit: one memory is cheaper than two.


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PostPosted: Sun Jul 03, 2016 3:31 pm 
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Yeah, but as you pointed out it's a giant pain to have to load everything into WRAM before using it, and you need something to boot from anyway. Personally I'd eat the cost and go with the more flexible option of putting bulk data behind the MSU1 and code and random-access data in a ROM.

If you can come up with an interface that maps part of the flash chip to the A bus as ROM (and possibly RAM), while preserving the streaming functionality for the rest of it (or allowing software-controlled mapping), without spending more on glue logic than you would have on memory, that's cool too...


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PostPosted: Sun Jul 03, 2016 8:26 pm 
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tepples wrote:
For the same reason some NES homebrew games have switched from battery-backed SRAM to a flash memory that can be programmed in circuit: one memory is cheaper than two.

Wasn't it because nobody likes the risk of the battery dying? =x

And yeah, my suggestion was to use the SD card for streaming the heavy stuff (in this case voice acting, but you could add FMV or other stuff like too) and the ROM for the usual game stuff (all code, the graphics you use regularly, etc.) And yes I know it's more expensive. Doing something that doesn't fit in the ROM is already expensive anyway =P


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