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Naomi Cartridge Buffer Chips

Papalati

Papalati

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I've got a few Naomi carts that are not booting and I read somewhere it is usually the small buffer chips. I'm assuming it is the small Fairchild buffer chips but all I can find are variants of the chip probably cause they are obsolete.

Does anyone know which variants of the Fairchild 74F245 can be used as alternates? Or is it a different chip?
 
no, it's the gamecode.
the roms/flash is usually just gfx/sound.
so if they find a bug it's simpler to issue a new eprom.
and for us it's simpler to install hacks like character enable's :D
 
stj said:
no, it's the gamecode.
the roms/flash is usually just gfx/sound.
so if they find a bug it's simpler to issue a new eprom.
and for us it's simpler to install hacks like character enable's :D
Click to expand...
That's what I thought. I checked the voltages on the pins and they definitely aren't hitting what they should be. A working eprom I have is around 4.45v on half the pins. The "bad" eprom reads differently. On the same pins that are 4.45v on the good one, half of those pins are 4.45 and half are 1.15. Basically it is every other one that is 1.15. So for example, pin 13 is 4.45 and then 14 is 1.15 then back to 4.45 on 15 and then 1.15 on 16. Where as each of those pins are 4.45v on the working one.

But like a noob I accidentally bridged 2 pins on the Xilinx chip next to the eprom while testing voltages. And a little burn smell later and I think the chip is dead. Replacement chip is like 20, so I'll probably order a replacement.
 
the xilinx are programable, so unless you have the code - wont work
also, the voltage readings dont mean much - the pins should be pulsing.
although if any arent then it could be a bad buffer chip
 
stj said:
the xilinx are programable, so unless you have the code - wont work
also, the voltage readings dont mean much - the pins should be pulsing.
although if any arent then it could be a bad buffer chip
Click to expand...
The pins definitely pulse on the working one, but do not pulse on the non-working one. I'm assuming you wanted me to put it in a eprom programmer and see if it reads it correctly? So, I have an adapter to read 42 pin eprom, but for some reason it says that the 2 pins on each end, of ANY 42 pin eprom, are invalid. Not sure what that's about and for some reason the chips aren't in the library of ICs for some reason. I think I'm gonna have to manually add the profile to get it to read the chips correctly.

As for the Xilinx, is it programmed to the individual game, or individual pcb? So, for example if I got another 18 Wheeler cart that worked and took the Xilinx off of that board and put it on the one not working would it work? And therefore if I got blank Xilinx chip and then programmed it from the working Xilinx from the good cart could I then use that to replace the bad one?

Thanks for all your help stj :)
 
stj said:
if it's 315-6213 then it's the same for all games on that pcb type
if you have a programmer that can read them then let people know!
Click to expand...
Yeah, its the 315-6213. So, I'll pick up a blank one online and program it when it gets here.

I did check the eprom finally and yeah there's no data on it. Any tricks to burning a new one or is it typical ic burning? Cause I still can't figure out how to burn a naomi bios. I'll try a chip or two while waiting your answer.
 
it's just a regular eprom - what programmer and adapter are you using?
 
Yeah, I went ahead and burned one and the data looks fine on the read. And now I don't have some funny business with voltages either. All the weird 1.15 pins are gone and are all now 4.45, like the good eprom shows, but no pulsing. Gonna switch to the buffer chips now. I'm using a TL866II Plus programmer.
 
866II+ can do 27c160 / 322 easy, i'v done them on one with a home-built adapter.
latest software is now 12.01 btw!
 
stj said:
866II+ can do 27c160 / 322 easy, i'v done them on one with a home-built adapter.
latest software is now 12.01 btw!
Click to expand...
Yeah I saw it flashing Upgrade Available but after downloading “the latest software” from the site it said I already had the latest. Which I don’t. I’ll figure it out.

I went ahead and ordered some buffer chips and I’ll go there next.
 
Well, after replacing several chips from a working cart I finally am able to boot the Naomi consistently to the test screen. But it still cannot identify the game. When I run a rom board test I get the attached result.

Any ideas what to try next?
 

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interesting
how does it handle rom select lines?
pld or something like a 74hc138?

it's a good console right?
the other thing to fear is the connector - try pressing down on it or using the screws - it's a real problem on dimm units
 
Plays other game carts fine.

Each line does a 5-10 sec “checking” and then spits out the data. So it definitely seems like it’s checking each ic.

I’m wondering if my eprom still isn’t burned correctly or if the selected ic profile I’m using is messing things up
 
dump the eprom and compare it to the original then.
and dump a working one - just to validate your method - i assume your bankswitching with an adapter
 
Original isn’t reading. I don’t have a working original eprom from the game for it because that would cost $180. All I have is a bin file I got off archive.org for the game.

I thought all I had to do was open the bin file into the buffer in xgpro set the chip settings and program. You saying I’m gonna have to do bank switching? Never found a good tutorial on how to do that properly for the 322. My knowledge for EPROM programming is like 3 out of 10.
 
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