nesdev.org

I have been making FF3 repros for a while and have had trouble with finding a good chr ram chip to work. i usually have to swap 2 or 3 out to get one that doesn't produce scrambled graphics.

i have tried all different kinds and can't find a brand that will work consistently. sometimes they work, sometimes not (eg, mosel, sony, sanyo, sharp).

does it have it have anything to do with the ts-rom board # or wram chip?

any help would be great!

coinheaven wrote:I have been making FF3 repros for a while and have had trouble with finding a good chr ram chip to work. i usually have to swap 2 or 3 out to get one that doesn't produce scrambled graphics.

i have tried all different kinds and can't find a brand that will work consistently. sometimes they work, sometimes not (eg, mosel, sony, sanyo, sharp).

does it have it have anything to do with the ts-rom board # or wram chip?

any help would be great!

It's more than likely the timing (speed) of the ram. 10 to 15ns I find works about every time.

nintendo2600 wrote:

coinheaven wrote:I have been making FF3 repros for a while and have had trouble with finding a good chr ram chip to work. i usually have to swap 2 or 3 out to get one that doesn't produce scrambled graphics.

i have tried all different kinds and can't find a brand that will work consistently. sometimes they work, sometimes not (eg, mosel, sony, sanyo, sharp).

does it have it have anything to do with the ts-rom board # or wram chip?

any help would be great!

It's more than likely the timing (speed) of the ram. 10 to 15ns I find works about every time.

ive been switching them out and still have messed up graphics. not really bad, sometimes only a little bit. i would like to know if there is a chip that works everytime, i am going through so many chips.

The PPU is faster than the CPU so no, don't use 150ns chips as CHR RAM. You will be surely frustrated ... lol

I'd suggest you go around "computer graveyards" and look for old 386s and 486s as their cache memory is VERY FAST SRAM memory (15ns/20ns, not 150ns) is usually socketed and can be bought for pennies most times. I have a box with like 60 62256 chips ranging from 30ns to 15ns.

Nintendo used 100ns chips, so just buy some online. Maybe even look at the 32KB chips as they might be cheaper.

http://bootgod.dyndns.org:7777/profile.php?id=1019

(To show what they used, thanks so much bootgod!)

3gengames wrote:Nintendo used 100ns chips, so just buy some online. Maybe even look at the 32KB chips as they might be cheaper.

http://bootgod.dyndns.org:7777/profile.php?id=1019

(To show what they used, thanks so much bootgod!)

yea i was checking his board scans, they used all different speeds, 100,150,200. any idea where i can buy new ram chips?

I've not once had a problem with 6264 hitashi chips for use as CHR-RAM including FF3j (that I can recall). I'll check the speed on the ones I'm currently using and report back but I'm more than sure they are 15ns.

As for where to buy them I kill 2 birds with one stone alot of the time and strip the static ram out of NOS atari 7800 cartridges. That way I got the SRAM for other carts and a viable donor for 7800 games. You can buy NOS atari 7800 titles that include a 6264 and a 74139 for between 1 to 4 dollars per unit and they are avalible in bulk.

Is any ram chip out of a nes cart suitable for this? For example can I take the chr-ram out of a Pro Wrestling cart and use that? What about the ram chip on a TSROM board? I see various labels like WRAM, SRAM, etc but I've never seen it explained if there is a difference.

FrankWDoom wrote:Is any ram chip out of a nes cart suitable for this? For example can I take the chr-ram out of a Pro Wrestling cart and use that? What about the ram chip on a TSROM board? I see various labels like WRAM, SRAM, etc but I've never seen it explained if there is a difference.

The only requirement is that it's faster than 100ns.

If it's a 6264, you just "drop it in" and should work. Again, the speed has to be 100ns or faster.

l_oliveira wrote:The only requirement is that it's faster than 100ns.

Where did this come from? Nintendo used plenty of CHRRAM that was slower than 100ns. The PPU runs at ~5.4MHz, so you should be able to use any CHRRAM that's faster than 180ns.

Searching Bootgod's db found ~440 games with CHRRAM and no PRGRAM. Of those games, their SRAMs are: ~40 are unknown speed, ~10 use 70ns, ~90 use 100ns, ~170 use 150ns, and ~130 use 200ns. (I suppose the slowest one works because all memory accesses have the address bus stable for a whole cycle before /RD is asserted).

l_oliveira wrote:

FrankWDoom wrote:Is any ram chip out of a nes cart suitable for this? For example can I take the chr-ram out of a Pro Wrestling cart and use that? What about the ram chip on a TSROM board? I see various labels like WRAM, SRAM, etc but I've never seen it explained if there is a difference.

The only requirement is that it's faster than 100ns.

If it's a 6264, you just "drop it in" and should work. Again, the speed has to be 100ns or faster.

most of the ram chips on nes boards are more than 100 ns, some are 80 but i have not used them. not sure why some work and some don't.

coinheaven wrote: most of the ram chips on nes boards are more than 100 ns, some are 80 but i have not used them. not sure why some work and some don't.

Like I said, CACHE RAM for 486s is the perfect chip because not only it's a hundred times faster than what you need on a NES, it's also free or very cheap and more than often comes in bunches of eight or nine.

I know this is going to come back to bite me .. but oh well.

NO .. it doesn't matter what chip you use for SRAM. I've never ran into an SRAM that didn't work as CHR-RAM for FF3j.

You have a different problem (which I discovered back in 2001 when I started selling reproductions) I have fixed dozens of "other" reproductions (customers sending me reproductions to fix that have pre-maturely failed) and they all have the exact same problem.

THE WIRE YOU USE IS SH*T.

You can't use 26, 28, 30, whatever gauge solid core wire in making reproductions! I know it's cheap, but it's wrong. You have to use multi-strand wire. Years ago, I was using old IDE cable, but I now have a supplier which sells me spools of the wire. It resists cross talk better, and you can run it for longer lengths.

The problem with the CHR-RAM chip is the CHR enable wire. It's the longest wire in any reproduction (pin 56 on connector) and picks up a lot of noise, and feeds it into the CHR-RAM chip.

Sorry for the rant.. tired of fixing bad eBay reproductions.

At 1.75Mhz crosstalk is the lest of your concerns, honestly. My FUGLY C163 cartridge would not even boot a game if it was a issue. 8)

leonk wrote: You can't use 26, 28, 30, whatever gauge solid core wire in making reproductions! I know it's cheap, but it's wrong. You have to use multi-strand wire. Years ago, I was using old IDE cable, but I now have a supplier which sells me spools of the wire. It resists cross talk better, and you can run it for longer lengths.

This is 100% untrue. I suspect the problem you've been seeing is repros made by people who don't know how to strip and solder wires, so rewiring them fixes the problem, because the actual problem was an open circuit, or a rosin joint.

stranded wire is no different from solid wire at NES speeds, especially because the strands are not insulated from each other- this negates any AC benefit. For there to be a benefit at AC (and this benefit is mainly lower resistance due to skin effect which isn't too useful here) is to individually insulate the strands from each other.

I prefer to use solid wire when making most things, because it stays in place better and doesn't flop around. It's easier to solder without having to tin the end of each wire to prevent loose strands flying around.

If solid wire didn't conduct logic signals as well as stranded, I'd be sunk. None of my projects would've worked.