NEC 3100/3500: slow! very slow!

I have got a NEC3100 in two of my Dell GX280. After applying Liggy’s conversion tool (3100->3500) I have applied several firmware updates: NEC original 2.18, MadDog 2.F9, Liggy’s 3500 bitsetting firmware 2.1A. After every update I have made CD/DVD reading and writing speed checks with different media (RICOHJPN R00, Princo DVD-R V1.02, TTH01,…) and all results show that whatever the media I cannot read above x2 for DVD and x12 for CDs! This is established using both nero CD-DVD Speed 4.51.1 and DVDInfoPro. I did exactly the same tests using the same bunch of media with an external Sony DRU710A and all results are much better (DVD read goes to x8 and CD to x32-x40 as expected). I have to add that all tests showed the same trend on another Dell that has exactly the same config.

I am clueless, I do not know what happens. Everything is ok except the speed: the device can read and write DVD+ and DVD- which makes me thinking that it is truly become a 3500 then why this bottleneck in speed?

Thanks a lot for your great help,

Enable DMA mode for the drives in Devicemanager.

Thanks a lot. That did indeed the trick.