On Fri, 05 May 2000 22:56:42 -0600, Warner Losh <[EMAIL PROTECTED]> wrote:
>In message <[EMAIL PROTECTED]> Warner Losh writes:
>: However, it won't work if you are hacking pci hardware and manage to
>: hang the PCI bus.
>
>Unless, of course, the trap handler is in cache as well as the
>debugger routines you need.
I thought the PCI bus was isolated from the CPU<->memory bus so this
couldn't occur. The trap handler should start OK, but just can't do
any I/O because the PCI bus is hung.
> There's not a good way to force it
>either since if you knew you were about to hang the pci bus, you'd not
>do the action that would hang it :-).
At least on the 486, it is possible to freeze data in the internal
cache by loading the cache (either via the test registers or by
judicious memory accesses) and then disabling it (CR0.CD = 1). It's
not possible to freeze specific cache lines. I presume similar
facilities are available in the later processors and for external
caches.
Peter
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