Hi
this is quiet difficult to explain some Cards are fitted with 2 seperat ram Banks ie 2x 128mb with two seperate addresses and the mediator and 0s4.1 only pick up one of These Banks giving 128mb.its more to do with the gfx Card bios i think.This was done for stability reasons.
Some really old Saphire Cards are 5v 3v compatible and work straight out the box no Problem but it like playing russian roulette if it works or not.
And the notches on some of the modern Cards doesn,t really apply to the 3v or 5v rule. confusing really.
I bought the Card which i linked to and used this link to do the mode
http://mfilos.blogspot.de/2012/03/a4000-modding-and-testing-ati-radeon-on.html Please note the Card has to be exactly the same in the Pictures hence the first link i sent you from ebay to garentee it works on the A4000DI,i bought from this guy in ebay modded it and it works perfect in the 4000
showing full 256mb.Ps(my Card had a venlitator fitted but physically the board is the same).Your Basically Making the 3.3v link with the regulator
But to confuse things even more it Show graphic trash in my A1200 ppc wich has one of the first A1200 Mediator pci boards fitted wierd.
But this Card does work in the A4000 DI MK and 1200TX.
Hoped i Helped you out a bit. if you still have your doubts ive still got the original Card from elbox only used a hour to test. or a Voodoo 3000. i could send over to the Homeland. as i live here in Germany since 30 years and my English is a bit Rusty lol.
Nobby