| T O P I C R E V I E W |
| Gnomesruletheearth |
Posted - 02/21/2012 : 11:31:40
I recently received gq4x programmer and am writing on 27c256 and 27256 chips. From what I understand they can hold a max of 8 megabytes. I write successfully which writes rather quickly. I even tried writing a 15 megabyte file out of curiosity and it wrote successfully. I thought it could only hold 8 megabytes though. I do not understand what's happening. I'm trying to burn nintendo nes games onto these chips and everything is soldered correctly on all my circuit boards. Ran volt meter through every trace and they are all good. If someone has had this happen I would very much appreciate any help. Thank you |
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| Gnomesruletheearth |
Posted - 02/23/2012 : 07:48:56
Thanks! My chips weren't big enough. Was able to program smaller game. I will be getting some of those chips you suggested for larger games. Appreciate your help. |
| chykn |
Posted - 02/22/2012 : 09:32:43
The chip model number usually reflects the number of BITS. So a 27c256 is 256Kb (bits is lowercase b) which translates to 32KB (bytes is uppercase B). You would need to use four 27c256 chips to hold a total of 128KB. Larger chips such as as the 39SF010 reflect the number of Megabits. A 1Mb chip holds 128KB, 2Mb holds 256KB, 4Mb hold 512KB and so on. |
| Gnomesruletheearth |
Posted - 02/22/2012 : 08:30:27
Ok, how many times do I need to copy my rom if it's 128 kb and I'm using 27c256 and 27256 chips? I thought it was once, the chips are 256 kb right? |
| Bad_Ad84 |
Posted - 02/22/2012 : 00:10:29
Nothing wrong with 27x - just that if you do not already own a UV eraser, it is something else you need to buy. |
| Gnomesruletheearth |
Posted - 02/21/2012 : 20:05:50
Ok, so my chips aren't big enough is what you're saying? I do have a uv eraser which I bought with programmer but you're saying the 27X chips cause problems? I appreciate your help and will look into those other chips. |
| chykn |
Posted - 02/21/2012 : 16:30:56
You'll have two problems with this setup.
1. That specific cart uses a 128KB mask ROM. You need to use a 1Mb (not 1MB) chip such as a 29F010 or 39SF010. Try not to use a 27xxx series since they're usually either OTP or require a UV eraser. Look up SST39SF010A on Digikey. You can get a larger one (39SF020 or 39SF040) as long as you duplicate the code to fill the chip.
2. The 28-pin 128KB mask ROM does not have a 28-pin flash equivalent, so you have to use a 32-pin flash chip. This means you have to either run wires from the 28-pin socket to a 32-pin flash chip or etch a custom PCB adapter.
Here are the common NES ROM pinouts...
h**p://nesdev.parodius.com/NES%20ROM%20Pinouts.txt
Regarding the CHR-RAM chip, you are correct. You should not need to replace it. This is assuming that the donor board is in fact an AMROM-01 board. |
| Gnomesruletheearth |
Posted - 02/21/2012 : 15:33:45
Oh to add, am I correct of the fact I only need prg chip in this board? From what I understand chr ram does not need to be removed. Thanks |
| Gnomesruletheearth |
Posted - 02/21/2012 : 15:30:10
I'm using an amrom-01 board right now trying to copy beetlejuice (I believe of the same pcb class and mirroring as my donor.) I'm curious as to why the programmer reads, blank checks and writes the chips successfully even with more information than it should hold. There is never an error such as "too much information to write" I find that odd. |
| chykn |
Posted - 02/21/2012 : 14:56:52
The 27c256 chips are only 32KB. Even some of largest retail NES games (Dragon Warrior 3 & 4) only top out at 512KB. Just out of curiosity, what donor cart are you using? Assuming it takes a 28-pin DIP, you should be able to just drop in a 28-pin flash chip. Larger chips usually require cutting traces and rewiring the cart (like SNROM) since the 32-pin NES mask ROM chips have different pin assignments for the address lines. |
