As part of my work creating the cave bug quick swap system, I decided to spend some time testing compatibility of the CV1000B library on a Bootleg CV1000D PCB. There was a lot of misinformation about this online and due to the RTC battery being removed, people thought the CV1000D had no RTC. This led to it being spread that Ibara wouldn’t work on a CV1000D. I don’t know why people thought this as U10, the RTC/EEPROM chip, is still populated. The RTC/EEPROM also stores unlocks, highscores and dip settings for all CV1000 Games. Still, it was unconfirmed and I wanted to test this for myself.

At first everything was appearing to work, I got through a handful of games and they would boot and play as normal. Ibara was good, Ibara BL was good etc. Then I got to Pink Sweets. No matter what I did, when i would turn it on I’d be left with a blank screen.

At first I thought this was a soldering issue. I’ve admittedly messed up quite a bit when I began working on modding my CV1000 PCB. Its extremely easy to bridge pins or even miss pins entirely. Some pins may appear to be soldered but actually aren’t. Its quite annoying and took me a long time to get the skills to do this consistently (hint: Use a good clean iron, a shit tone of flux, and good solder. Or just invest and learn hotair). Even after going over it a million times I couldn’t get it to work. I gave up and moved on to testing Espgaluda 2, but I was getting some pretty major graphic glitches so I stopped for the night.

Sick of soldering the flash all the time, I invested in some TSOP48 ZIF Adapters. With these installed on my mod PCBs I no longer needed to worry about soldering and de-soldering flash. I was able to test Espgaluda 2 and confirm it worked, and then got through the rest of the library quickly.

zif socket
A cheap TSOP48 ZIF adapter that can be installed on any standard tsop48 footprint

To my surprise EVERY other game worked fine. All Except pink sweets, which still gave me issues.. I tried quite a few times, and even tried the suicide club rom, resulting in the same issue. LED D6 would turn off and I’d be left with a blank screen.

Pink Sweets had quite the patch cycle and as a result has plenty of revisions. This whole time I had been testing with the “2006/04/06 MASTER VERSION….” rom, which the base rom for mame and the version the suicide club mod is based off of. I decided To find one of the older revisions and try it out.

Success..? It worked, but why. Maybe my other rom dump is bad? but it works fine in mame. I had no clue.

I bit the bullet and pulled out a CV1000B PCB and flashed what I thought was a bad dump. It worked fine.

By this point I was very confused. I had confirmed the rom dump was good. It worked on mame and on a CV1000B pcb, but not my CV1000D. Maybe there’s an undocumented difference between the CPLDs? So swapped them and still had the same issue.

Throughout this I had neglected investigating the major difference between a 1000D and 1000B pcb, Its SDRAM. After posting about this compatibility issue online I got some suggestions that maybe it a was a ram timing issue. My bootleg CV1000D has a IS42S32400 7TL SDRAM chip installed. So I asked online if anyone with a legitimate CV1000D could confirm what their ram was. Well, it turns out a Akai katana PCB uses a IS42S32400 6TL chip.

The 6TL SDRAM variant supports a higher clock frequency of 166mhz, compared to 143mhz of the 7TL. Sure enough after checking the datasheet of the CV1000Bs ram, it also boasts a frequency of 166mhz. Fortunately I had a mouser order I was filling up and threw in one of the SDRAM chips to test.

Once it arrived I swapped the chips, flashed pinksweets “2006/04/06 MASTER VERSION….” and sure enough it worked. As a sanity check I went through every other game again and confirmed they still worked.

Success!

With this I can confirm that all publicly available versions of CV1000 games are compatible with a CV1000D PCB once upgraded to using the 6TL Ram.

TLDR: For full compatibility on a CV1000D PCB, Replace IS42S32400-7TL with IS42S32400-6TL