🚀 go-pugleaf

In article <20321@cup.portal.com> stephan@cup.portal.com (Stephen Derek Schaem) writes:
>
>     I need information about the lucas and the supra 4x4 scsi
> controller.
>  don't have a 68881 for the lucas board (working at 25mhz like a
> charm, 74F74) so I don't the little hack of connecting pin 7 and
> 15of U7.
>           
>     The problem is that the supra controller is not 'working'
> like it wasn't even there... It it cause by the U7 'trick' or
> simply or having the lucas board?
>
I had a Supra controller working with the Lucas board, but it would not work
reliably at 20 Mhz. It would work at 16 though. You may have to slow things
down. You can also try different chips in the U9 position. On my particular
machine and many others, I have had best luck with a National 74LS74AN. Note 
that the brand is critical too. You should try LS, F, ALS and plain 7474
parts from DIFFERENT manufacturers. I have found that some 1000 motherboard 
just don't work well no matter what is done.

>     Also, How will Fransis react with lucas at 25mhz? I want to
> keep it at 25mhz since I really saw a difference between 20 and
> 25mhz, and everything that work at 16mhz work at 25.

You will have a problem running the Francis board this fast unless you get
REAL fast ram chips. Even then it might not work. The problem is that above
16 Mhz or so, you have to insert extra wait states (wasted clock cycles)
because the ram cannot keep up with the CPU. I don't yet have my own Francis,
but according to Brad Fowles, the designer, the system is faster running at
16 Mhz with 1 wait state ram than at 20 with 2 wait states. You MAY get it to
work at 20 with one wait state as I think some people have had limited success
at this. 

<<<Doug>>>
douglee@becker