Subject: Re: VAXstation 4000/90 Success!
To: None <firstname.lastname@example.org>
From: Hugh Graham <email@example.com>
Date: 07/14/2002 13:37:56
On Sun, Jul 14, 2002 at 09:21:52PM +0100, Matt wrote:
> > Then: E/P/B 200A0009 and see if it changed. If it didn't change, we
> > may have to fix this from kernel mode since the monitor would appear
> > to have a sanity check that the os isn't subject to. A hacked version
> > of the dz probe itself should do the trick.
> I can enter the command, and the VAX doesn't complain, but the value
> remains unchanged, still 00.
Ok, it must have a sanity check. I'll see if I can figure out a quick
hack to write there from kernel mode. It's actually surprising that the
machine (apparently) allows this area to be written at all.
> Actually, having picked through the dump in my hand patching, the end of
> the image is all 00's apart from the last 4 bytes. Would this be the
> checksum of the firmware perhaps?
I think it's likely that when DEC increased the firmware from 256KB in
4k60 to 512KB in 4k90 they just had a lot of space they didn't need.
Those last 4 bytes could well be the checksum, but I have no idea what
method they use to derive it.