In conclusion, it is PCB layout issues causing hard drive problems. Slower TTL devices, along the lines of the 74LS series were simply not fast enough to respond to the PCB noise and worked correctly. Faster TTL devices or even cmos devices can react to the noise and generate bad signals causing problems. In none of my tests with DMA chips did I find any difference. I thus conclude the "Bad DMA chip" is nothing more than a myth.

Si j'arrive a mettre la main sur un gigafile ou un ultrasatan et que mon "vieux" DMA pose soucis je tenterais, ce n'est pas deux capa qui risque d’endommager quelque chose

(plus de details ici: http://exxos.www.idnet.com/IMPULSE/atari/last/gigafile/index.htm )