I'm trying to piggy back two region free bios chips on top of the retail bios. The intent is to have a single toggle with three positions. One position for the retail bios, second position for region free bios, and the third position for dreamshell boot loader bios. I'm installing this on a VA0 board. I piggy backed the first bios chip on top of the retail one and tested it. Everything worked great, but after I stacked the third chip, and left the power still connected to the second chip and I tested it, I'm getting a black screen. Does anyone know what I have to do in order to make this happen?
Maybe explain how you're trying to wire it up? Your picture isn't very clear. It probably would have been easier/cleaner to put the 2 new BIOSs on a single 4M chip.
I'm wiring it up the same way you would wire one of them up. Just another stacked on top of it. It's a VA0 board so wires going to 1 and 23 are swapped. Leg 1, 12, 23 raised. Leg 22 is down on both chips. After the first chip was installed I tested it and made sure it was working and then did the same for the chip above it. I had the other resistor in place but I started trouble shooting and this was the state I left it in and took a picture. If I power any of the chips, I get a black screen. I wasn't aware you could load two Bioses to a single chip. How would you select which one to boot?
Provided you have the CS/ pins on the unused chips tied high, it should work. Basically, you need 3 10K resistors, each of which pulls up the CS/ pin from one of the chips, and then connect the signal from D501 to the chip you want to enable. If you have two images in one chip, you just use the highest order address line to select them. So in this case, you need A0-A19 to address the 1M words of space, and the A20 pin would select between the two images.
If you just stacked the two new chips then they're both active at the same time and that won't work. Your /CE pins should be tied high, which it looks like you're trying to do through a resistor to VCC on the chip, but it looks like all the /CE pins are connected? And your switch needs to bring /CE low for the one chip (and only one chip) you want to use which I don't see any evidence of in the pic. To use a chip with 2 BIOSs you get one with twice the capacity and switch /CE to select the original/new chip and use the high A line to select which BIOS on the new chip to use. Note that /CE is active low and A is active high.
Only the retail chip has the CE pin with a 10k resistor to the VCC. The middle chip has the CE lifted with a resistor going to pin 1. The same will go for the top chip(If I'm not mistaken). I don't have the CE's connected to each other, each one is lifted. I didn't do anything with the top chip and it's lifted legs. I'm not sure I understand what to do when you say bring /CE low for chip I want to use. Can you explain how I could set that up?
High = voltage is high Low = voltage is low Basically it's high when there's a big resistor between the pin and ground (or none an open circuit, but that's not clean) and it's low when there's a small one (or none, a short). See http://en.wikipedia.org/wiki/Pull-up_resistor
OK, thanks for the input everyone. I think I understand the problem more now, but I'm still not sure how or where I should be wiring these resistors to make them work with a toggle switch? I plan on using a DP3T or ON/ON/ON toggle. I'm sort of a noob at this I guess, if anyone with a better understanding of electrical circuits could give me some advice, I would really appreciate it.
Pardon me. I am aware of dreamshell. But may I know what is a "dreamshell boot loader bios"? What does it do? What are the benefits? Thanks.
It loads up dreamshell without the need for a "startup disc". The sd card adapter/reader is still required.
Correct me if I am wrong. So the entire dreamshell.cdi (which is around 600mb) is now stored on a chip?
Well the goal for me with this project is to be able to boot directly to dreamshell, so that I can then use dreamshell to load games directly from an IDE hard drive. I do't want to have to use the GD-ROM drive at all, but I do want to retain the original functionality of the console if I want to spin up a disc.
