>>>>> "Gaixia" == Gaixia Zhang <[EMAIL PROTECTED]> writes:
Gaixia> We want to use with Bus Arbiter. From EBSA285 reference
Gaixia> Manual, then the
Gaixia> image selector switch can not be used. So I think I must
Gaixia> erase PBL/Angel
Gaixia> and program bios in image 0. But I think AIF format depends
Gaixia> on PBL/Angel, the PBL/Angel is not there any more, how bios
Gaixia> get started?
Gaixia> If we enable X-Bus, do we need some additional hardware to do
Gaixia> Bus Arbitration?
Yes, that's an ugly design mistake in the 21285. I was told this was
done to save a few dollars on the package (256 pins isn't enough to do
the right thing, and bigger packages cost more). One of the silliest
design compromises in recent history, that one...
Anyway, a good solution if you can use it is to use the backplane that
DEC built for the EBSA285. It has a PAL on it that does the
arbitration, so you get to use the X-bus.
If you get that backplane, be careful to order the right version.
There are two, one for 5V PCI boards and one for 3.3V boards. Most
boards seem to be 5V. If you get the 3.3V board, you will not be able
to use 5V boards -- partly because the voltage isn't there but mostly
because the edge connectors are keyed and your cards won't fit. (The
difference between the two boards is (a) a few jumpers and labels, and
(b) the keying of the PCI connectors.)
I think the eval board kit comes with the design files for the arbiter
PAL. (If not, then the backplane kit does, and I also once found it
for download on the Strongarm website.) So if you want to use your
own backplane you could add an arbiter PAL of your own to it.
paul
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