Help burning NAOMI BIOS ROMs

[MetalliC]

that's what I had thought but it struck me as strange that it looked so different from the Sega Rev H chip that I had. maybe it got corrupted during the download or the unzipping. I suppose it couldn't hurt to grab it again.

Naomi (as well as other Dreamcast-like hardware) BIOS is protected from modification, by checksumm made by chipset hardware. side effect of this - if you burned BIOS ROM somehow wrong, or target EEPROM was bad - it won't work at all.

in multi-bios, using that (different from regular H-bios) 1KB bootstrap the rest of code and data made moddable

 

[Krankshaft]

Before you give up programming those chips try modifying the write VCC in the GQ-4X software it's set to 5.5 volts for the M27C160 when in the datasheet it says VCC should be raised to 6.2 volts when programming.

Make it a habit to click the i button next to the selected chips name to view the voltages the programmer is set to. Too many people (myself included until recently) ASSUME the voltages for the chips are correct and have read and programming issues as a result. Always pull the specific manufacturer of your EPROMs datasheet and compare the voltages.

This isn't isolated to rare EPROMs that aren't encountered often.

For example by DEFAULT the generic 27C256 EPROM which practically everyone programs at one time or another has the VPP set to 12 volts and RVPP is set to 5.5 volts this is WRONG. It should be 12.7 volts VPP and 6.2 volts RVPP. Will many EPROMs program at this improper voltage? Yes but some won't and you can't be confident the EPROM bits were cleared reliably at those voltages (the proper WVCC makes sure each bit is programmed to a high threshold voltage for example).

I had this issue with a M5L2764 (21V VPP) EPROM I was programming recently it stopped dead at 8% setting the WVCC properly at 6.2 volts allowed me to program it.

To change the voltages go to the devices.txt file in the GQ installation directory make sure the application is closed.

Find the following line in the text file:

Name="M27C160",ID="XXXX",Class="27C800",Category="EPROM",MFG="ST",CodeSize="2097152",Adapter="ADP-054, ADP-055 16 BIT EPROM ADAPTER",RVpp="5V",WVCC="5.5V",WVPP="12.7V";

and replace it with this text line:

Name="M27C160",ID="XXXX",Class="27C800",Category="EPROM",MFG="ST",CodeSize="2097152",Adapter="ADP-054, ADP-055 16 BIT EPROM ADAPTER",VCC="5V",WVPP="12.7V",WVCC="6.2V",BVCC="5V",RVPP="5V";

Also FYI this is a list of the VCC and VPP voltages the GQ-4X can supply if you type an invalid voltage it will inform you when the application is opened.

VCC Voltages:

3.6V
5V
5.5V
6.2V
6.5V

VPP Voltages:

3.6V
5V
12V
12.7V
15V
21V
25V

If it still doesn't program it's a software issue that needs to be addressed by support. They're pretty good with tech support I had a Dallas DS1220Y BBSRAM that didn't read properly and they asked me to mail the part to them so they could fix the issue they fixed the issue and released a new version of the software.

 

[twistedsymphony]

Naomi (as well as other Dreamcast-like hardware) BIOS is protected from modification, by checksumm made by chipset hardware. side effect of this - if you burned BIOS ROM somehow wrong, or target EEPROM was bad - it won't work at all.
in multi-bios, using that (different from regular H-bios) 1KB bootstrap the rest of code and data made moddable

That makes a lot more sense. Last night I burned p1pkin's NAOMI1 H bios and his NAOMI2 C bios onto some brand new chips and both are working perfectly.

Before you give up programming those chips try modifying the write VCC in the GQ-4X software it's set to 5.5 volts for the M27C160 when in the datasheet it says VCC should be raised to 6.2 volts when programming.

...

thanks for the tip, I'll give that a try and hopefully I'll be able to make use of those older chips instead of tossing them!