matters the size of the sav file
the size of the sav file may matter
whatever. haha
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matt's mind
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Germany
well there are other types of sram chips with more memory. so basically, if you could find one with lots of space that fits for an ems cart, you could make multiple lsdj saves!
but idk about the sram of the drag n derp cart, so it may not be rentable as youll spend about the same money on the mod.
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matt's mind
no, i'm saying (if people are thinking LSDJ with this), that IC is 32k, lsdj save file is 128k (unless there is a bit/byte difference going on here, i just skimmed over the specs, and didn't particularly note the 'b' or 'B')
will work for some ROMs, but not all of them. the reason the IC is drop-in compatible is because ramtron designed them for precisely that purpose (i would imagine the datasheet mentions something about drop-in compatibility with SRAM in the intro). ramtron has put out a lot of fram chips with the same pinouts as common sram equivalents. so on 32k RAM carts/games its not an issue. which doesn't mean lsdj unfortunately, or else it'd be a simple scramble to get a rom ic replaced with an eeprom or something, and voila... polish student/smartboy/bleepbloop/mbc5 -esque fram flashcart courtesy of a nintendo pcb!
i'm very aware of this sort of thing because i laid out a PCB (which worked fine otherwise, incidentally) and due to an idiotic misreading it's ram size was not large enough. same scenario this thread is touching on really. but, that's corrected and *soon* but its still a big face palm every time i think about it... pretty embarrassing to say the least. but it taught me a good lesson in paying attention to capitalization with zeal (which i've obviously not learned yet 
).
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Germany
well, the FM18W08 has 8x32k, so 256k 
shouldnt be a problem, unless the gameboy cart only can address one of the banks. if thats the case, well have to look for a 1x128k or more.
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Jelly Stone park, MD USA
Bamboori wrote:
well, the FM18W08 has 8x32k, so 256k
I think you are confusing bits and Bytes. Without researching this chip in particular, the common convention is to list the bit size of a device - 256Kbit or 256Kb, this can also expressed as 8x32K. as in a 32KByte, 32KB device. This can be very confusing, but manufactures use the bit size because some devices can be used in 8bit or 16bit data bus systems. I think Kitsch mentioned the pitfall of this mistake ( I feel your pain Kitsch, have done the same!!).
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Germany
whoops ._.
but maybe theres a chip with enough space... if not, then its at least useful for other music programs i hope
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matt's mind
32,768 words x 8 bits (or whatever the exact # is)
that sort of thing
its not really a straight multiplier like you'd think (32x8), its telling you how the data is grouped. just written that way to identify its architecture, so to say
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Jelly Stone park, MD USA
OT, sort of:
http://en.wikipedia.org/wiki/Ferroelectric_RAM
wow, I so misunderstood the tech with a FRAM, thought it was a form of Flash. A new take on the old woven ferro core memories!
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Huntsville, AL
yogi wrote:
Generally, RAM chips hold their data down to around 2V, but check your data sheet for specifics.
I would suggest that you approach the charging problem with a automatic circuit, charging the battery when the cart is docked. Dallas Semi, and I'm sure others did also, used to make a RAM supervisor chip to control switching from mains to batt.
There is never going to be a 100% fail-safe design; the batts will drain if the cart is left in a box for years, or the batts will fail over time with reg use. Battery backed RAM is not a permanent media, could be why we don't see too many RAM based devcarts.
For truly 'safe' you need to back it up. A batt will buy you some time, but only diamonds are forever.There are some newer chips out that operate as RAM and save to Flash on power fail, but speed and density may be an issue ATM.
So you're saying to put a game that uses a battery save, into a flash cart, and then backup the save onto whoever's computer, to keep from the battery dying, and losing the save.
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Huntsville, AL
thebitman wrote:
I've looked into the possibility of throwing FRAM into non-FRAM flashcarts. Still on the fence about whether or not to do it, but technically there are drop-in replacements for chips I have isolated in some of my cartridges. Just want to let you know that option also exists though it has mostly gone unrealized.
What does FRAM do?
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FRAM is Ferromagnetic RAM (google it!), basically allows RAM to retain data even without a power source (like traditional RAM).
By the way, welcome fellow Alabamian. In Tuscaloosa, here.
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Huntsville, AL
katsumbhong wrote:
Getting a job usually helps your situation.
It's a joke. 
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Huntsville, AL
kitsch wrote:
matters the size of the sav file
the size of the sav file may matterwhatever. haha
Usually they're always 32KB, for the data that most all GameBoy cartridges save. I think LSDJ saves a MUCH bigger size.
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Jelly Stone park, MD USA
@ chowdit1: Short answer: back up your data, batteries fail. If your saves are important to you, have a copy on another media, whether it's flash or a floppy.
I'm not a GB user but the issue of saves is common to almost all embedded systems. I'm sure others can answer to the specifics of the GB,with ways to transfer saves from it. I know somewhere in one of these replies someone mentioned how they transferred their saves.
Yogi 
Last edited by yogi (Aug 6, 2013 6:29 pm)