2.7 Install Problem (Adaptec 2940UW time out)

["Gilles CHERIX" <gcx_(_at_)_bluewin_(_dot_)_ch>]

Hello everyone,

I've experienced a strange problem when trying to install the brand new
2.7.

The box I want to install on is a SCSI config based on a 2940UW adaptec 
controller, two harddisks (IBM and Western Digital) and a NEC CD drive.

When I boot from the cd or from a boot floppy it hangs saying something 
like that :
ahc1 board isn't responding
cmd failed
SCB 0x1d - timed out in Status Phase

it worked fine with 2.6 though.

I found out that if I disable the "wide sync" for these three devices 
in 
the adaptec bios, it can boot.

I'm just asking why it doesn't boot and if there's a way to fix it 
cleanly (and if not what is the loss of performance I can expect with 
"wide sync" disabled).

Thanks very much
Gilles