industrial computer flash performance issues

[WKK]

I have a Nagasaki IPC industrial computer that has an 8 GB flash drive 
on a 44 pin ATA connector. I have booted FreeBSD 6.2 and 7.0 via a USB 
CD drive and I am getting very bad read performance.

dd if=/dev/ad0 of=/dev/null bs=128k count=100 is only showing about 
4MB/s. I have also tried a CF via a PCMCIA adapter and I am also seeing 
about the same performance.

The same CF device connected with a USB adapter (/dev/da0) gets about 
16MB/s so it seems like some type of ATA driver issue.

>From dmesg:

atapci0: <VIA 8237 UDMA133 controller> port ….
….
ad0: 7765MB <JMAU FDM 8GB 2.0> at ata0-master PIO4

atacontrol cap ad0 shows that dma and overlap is not supported and all 
the features are no.

Does anyone have any suggestions for improving performance?