How about an external 3500 with GL811E(04) USB2.0 chip?


I recently saw this enclosure. It’s advertised as one of the fastest USB2.0 enclosure:

USB 2.0 High Speed Average Transfer Speed
GL811E-04 (~29Mbits/sec)
Other Vendors ( ~ 20~27 Mbits/sec )

What do you think? Will it reach 16x reading or will it creep at ~10x like the most other enclosures?


The thing to consider is those performance figures were obtained using hard drives, not optical drives. The problem stems from the fact that some enclosures do not set the proper IDE ATA mode internally for DVD drives. To get full 16X performance it needs to be set at UDMA2 (33MB/sec). Instead some enclosures are setting it at Multiword DMA 2 (16MB/sec). So it depends on the chipset inside the enclosure, and even then you can get different results between two different enclosures that use the same chipset but different manufacturers (brands). The best methodology seems to be find user experiences on different forums and/or a bit of trial and error on your part.

I ordered the above mentioned USB2.0 enclosure. According to the german c’t magazine Mapower externals with Genesys GL811E give the highest USB performance, minimum read/write 27mb/sek. I’ll test it friday night, so keep your fingers crossed for me :wink:

Edit: how can i quickly find out that UDMA instead of Multiword-DMA is running (without making speedtests)? I know the ide controller tabs in the hardware manager, but of course only for IDE controllers.