Sega Mega-LD BIOS Dump [PIONEER PD6126E] [1.05 JPN]

Archive · Post by **Archive** » June 27th, 2019, 6:02 pm

posted by Shane McRetro on Oct 7, 2016:

New Year's Eve 2013 and I figured I might crack open my PAC-S1 to check for capacitor damage... the good news, there's none! The even better news, an undumped BIOS? Version 1.05. I can find references to 1.02 and 1.04, but not 1.05 on the Googles. Have a look and if you have any of the other LaserActive PAC BIOS files that have been previously dumped, please do compare notes!

Download link

Edit: Interestingly to dump the chip properly via my GQ-4X with ADP-054 adapter I had to adjust the VCC to 3.6V instead of the typical 5V. What's even more interesting is the same had to be done on a uPD23C4000 chip from the Sega Channel Adapter I dumped a few weeks back... peculiar! Below is what was added into my devices.txt. Without it, the checksum just wouldn't stay the same.

Name="MBM27C1024A",ID="XXXX",Class="27C1024",Category="EPROM",MFG="Fujitsu",BufferMode="16BIT",Adapter="ADP-054",RVpp="5V",VCC="3.6V" ADP-055 16 BIT EPROM ADAPTER;

Edit 2: X-cult seems to have others listed with internal build dates;
1.02 US - 29th March 1993
1.02 JPN - 29th March 1993
1.04 US - 22nd September 1993 and now
1.05 JPN - 7th October 1993

Edit 3: Looks like my GQ-4X is headed to the trash pile! At least for EPROM chips. My TL866CS / TL866A is now my programmer of choice. It's strange because the GQ-4X can still read and write some things perfectly. I guess I'll keep it on hand after all

Archive · Post by **Archive** » June 27th, 2019, 6:02 pm

posted by Bad_Ad84 on Dec 31, 2013:

Having to set it to 3.6v for a 5v eprom (especially one that is actually an eprom, not a maskrom) is very wrong.

To the point where I am suspecting a fault with your programmer...

Archive · Post by **Archive** » June 27th, 2019, 6:02 pm

posted by APE on Dec 31, 2013:

IIRC my Sega PAC has 1.02 in it, probably should check just to be sure.

Archive · Post by **Archive** » June 27th, 2019, 6:02 pm

posted by coltonbios on Jun 23, 2014:

EDIT: It's Japanese. No need to worry.

Archive · Post by **Archive** » June 27th, 2019, 6:02 pm

posted by Shane McRetro on Oct 29, 2014:

Bad_Ad84 said:

Having to set it to 3.6v for a 5v eprom (especially one that is actually an eprom, not a maskrom) is very wrong.

To the point where I am suspecting a fault with your programmer...

As it may very well be burning out, what would be a suggested all round EEPROM / EPROM reader? (Mac support would be appreciated

Archive · Post by **Archive** » June 27th, 2019, 6:02 pm

posted by Nemesis on Oct 30, 2014:

Like you I also have a GQ-4X, but I've wanted to pick up this as well:
http://www.ebay.com.au/itm/181039406913
This would be my pick for another low-cost device. Unlike the GQ-4X, it supports GALs too, and it has lots of positive feedback and reviews, with a very large set of supported devices. This is the TL866A version, but there's also a cheaper TL866CS version which lacks the ICSP port (which you can mod+firmware hack the TL866CS to add manually I believe). The best place to buy it is on ebay. You can also get bundles which include a bunch of different adapters like this one (TL866CS version):
http://www.ebay.com.au/itm/320967107440

I don't know that I'd say this device would be a replacement for the GQ-4X, there are some devices that each support which the other doesn't but it would certainly compliment it nicely.

Archive · Post by **Archive** » June 27th, 2019, 6:02 pm

posted by Shane McRetro on Oct 30, 2014:

Thanks for the response!

I grabbed the TL866CS last night actually. I've got a PICkit 2 which can do the old PICs and even AVR chips! I can't believe I was able to compile some code to actually integrate the AVR something or other into the PICkit software, ramble, ramble. Too long ago. Works on Mac OS though! Woo! But you say the CS can be modded / hacked up to the A version (noted, but probably never will be done

I confirmed that my reader is definitely reading 27C1024 chips OK again, but not this darn Pioneer one. I am just not able to get checksum that stays the same! The one that was above (link now dead) works as far as I know but I wanted to triple check. I do have a copy of the BIOS if anyone needs it by the way. The thing is under recap mode at the moment in pieces everywhere.

I'm glad I bought the one I did - Now to wait three weeks for it to turn up

Archive · Post by **Archive** » June 27th, 2019, 6:02 pm

posted by Bad_Ad84 on Nov 2, 2014:

Happy for you to send me the bios to be dumped on my high end programmer. Will then return it

Archive · Post by **Archive** » June 27th, 2019, 6:02 pm

posted by Shane McRetro on Nov 13, 2014:

Bad_Ad84 said:

Happy for you to send me the bios to be dumped on my high end programmer. Will then return it

Thanks for the offer, but where's the fun in having someone else do all the work

Got my TL866 today, gave it a few reads and this is what it gave me. Different code to the original dump I did back above... GQ-4X mustn't like it?
If anyone wants to compare it with the original dump I did - it can be found here. Any help on determining which one is correct would be great!

Or if someone could teach me a thing or two about how to check for valid checksums, that would be teaching me how to fish

Archive · Post by **Archive** » June 27th, 2019, 6:02 pm

posted by Nemesis on Nov 20, 2014:

The new dump is the correct one. Comparing the two files shows the same pattern of bytes different between the two at exactly 0x2000 byte intervals. I can see that the new dump has valid code in these areas while the old dump is filled with 0xFF bytes.