DUAL BIOS SEGA DREAMCAST PLUG AND PLAY

nice. a piggyback installation but way easier, nicer, and cool looking.

 

Dragon city is still using the wrong chip for VA0 consoles...

I get concerned when people release things like this commercially with no understanding of how it works.

I will release the one I started years ago, but never got around to polishing up for release.

 

I use MX29LV160TMC and put 3.3V with VA0 Dreamcast so no problem

In the pcb you can choose the bridge VA1 for connect Pin23.
And if you don't bridge you use VA0 solder in the PCB for connect 3.3v.

And for finish the pcb it's sell alone so you can put the bios what you want

 

Yes, it is a problem.

You are using a 3.3v chip on a 5v bus. The address lines of the chip will be getting driven with 5v.

You do not understand the implications of what you are doing or selling. You have just seen a mod online and made a PCB for it. With no electronics understanding at all.

 

yeah using a 3.3v chip on a VA0 board would be a terrible idea, that said I don't see how dragoncity (willfully?) overlooking that invalidates the board design - it should be a good tool for VA1/2

 

The principle is fine, using the wrong chips and not understanding why its a problem, when its been explained to you - bad sign. If you don't know the basics of electronics, you shouldn't be making stuff commercially imo. At the very least - maybe listen to those that do!

https://assemblergames.com/threads/dreamcast-region-changer-on-jap-va0.69188/

 

I used MX29LV160TMC on many Dreamcast VA0 no problem,because I left the pin 23 and put 3.3V..not 5V...

I don't understand what is the problem when you use 3.3V for Pin 1 & 23 lifted on VA0..I know use 5V it's not good..but 3.3V..

 

regardless of what you're using for VCC the dreamcast is still using 5V for the bus logic levels

 

Hum hum..

I have a Dreamcast VA0 since 6 years no problem with this config.

And I tested many games for Dreamshell,so more than 6000 Reboot !!




And many dreamcast since 2 years again...and NEVER problem..never never never..with MANY motherboard,I tested more than 50 Dreamcast VA0 !

So maybe it's true but for me.. I don't see the problem.

For the PCB it's not a problem because you can put the bios like you want,it sell without the chip.

But I repeat for me..I have never had a problem...

 

"Works for me" isnt valid electronics design. Also, as explained in the other thread - I have sold thousands of these chips and I have had people have it not work. This is why in electronics you follow the specs - so it works for everyone!

The facts are - you are running the chip above its maximum rating in its datasheet. This isn't up for argument - its just a plain fact. This is why your design is incorrect for the VA0.

Its fine for personal use, but a commercial product it isn't. Posting an incorrect schematic that was around on the internet doesn't prove you are correct. Just means they got it wrong too.

Here is a corrected version.



Also, the VA0 chip has a different pinout - so you cant just have people put a different chip on the board.

 

I just give my return for 6 years now that I use the bios with the previous diagram, and never had problems.

I understood what you wanted to say, but here also understand that I would like to meet the concerns that you quote to tell me "shit they are right", but as said before I never met the problem.

Did you personally meet the worries?

 

Yes, as explained in the previous thread - I have had people send me the DC after they incorrectly bought a 3.3v chip and it not work.

I removed the chip - tested it in my programmer, tested it in another DC and the chip was confirmed working. I installed the correct 5v chip and the DC worked fine.

Yes, for the 3rd time - I have personally seen this not work. Not just the theory.

But if you want theory - you are running a chip above its maximums. If it fails, you will get a short on the bus and could damage the dreamcast. You shouldnt sell a product that is designed like this.

Just make a VA0 version with the correct chip!

 

I mean you could, it would be safe, just not field programmable

 

Yeah, but hes supplying them blank. Anyone with a programmer to preprogram it - probably doesnt need this anyway.

So its not going to work.

Edit:
After reading his post again, it sounds like it is just an unpopulated board rather than the bios on it thats blank. If someones going to need to solder the chip to the PCB, whats the point?

 

cleaner than a piggyback if you want to retain retail bios as an option, plus it's easier to solder SOPs than to desolder them

you sell preflashed chips right? so does the bloke in canada

 

I do. But then why not have a PCB with the chip footprint and pins 1 and 44 broken out - you can use either type of chip then with no issues.
It would be a minor redesign, would be designed correctly and most importantly - stop me moaning lol.

But I have just spent the last few hours finishing up the design I had been working on ages ago. It will come with the chip fitted and solders the bottom of the PCB.

Will report back once its ready for sale. Will come in the correct versions for the different versions of DC.

I should probably finish up my sata hdd adapter too - I finished the PCB layout over 2 years ago! Time flies and all that.

 

I agree, he would be better off doing away with the VCC jumper pads and using the space for two more weak pullups and a write enable to 1 or 44 pad

 

just for curiosity its va1 same as va2? pinout? voltage? i thing yes. but i would like to hear it from more professional guys thanks.

 

Yes, va2 is the same pinout and voltage as va1, the piggyback mod or direct replacement is exactly the same, except for the point that links to leg 44 of the new chip.

 

For you, Bad_Ad84, there is a lot of things to change for VA0 ? Which chip instead of MX29LV1 did you recommend ?
Dragoncity do the best job as he can, he doesn't want damage anything.