Subject: Re: bankeddev for Retina?
To: None <firstname.lastname@example.org>
From: Niklas Hallqvist <email@example.com>
Date: 09/22/1994 10:34:59
>>>>> "Chris" == chopps <firstname.lastname@example.org> writes:
>> Is banked device support still in 1.0, if so, where can I get the
>> bankeddev.h file? has anyone gotten MW's server to run under 1.0
Chris> Oh BTW the reason its needed I suspect is that the retina Z3 is
Chris> addresses as a flat memory device unlike the Z2 which uses
Chris> banks of 64k. The BANKEDDEV code faulted the correct bank in.
Chris> The problem is that the code is usuall much slower. Consider
Chris> drawing a circle.
Chris> On a banked system you would optimize by drawing only once per
Chris> bank however on a flat system you just do the fastest
Chris> algorithm. The later gererally causes many faults/banks
Chris> switches as I understand it.
This may be all moot, but...
Wouldn't it be possible to lazily do all operations in some sort of
bank cache. When a fault occurs in a bank not cached, save the
previously mapped bank, if modified, in the cache, schedule the bank
for update later and map the copy instead of the bank being lost. Then
map the new bank. Maintain a modified bit for the banks. Scheduled
banks for update could be handled at the next vbl or maybe even a
vbl later than that.
I'm not ready to go ahead with this. I just thought I should throw out
a weird idea.
However, I have seen a real bug I think. The Z2 Retina seems only to
allow 16K of chars sized screens. Shouldn't it allow 32K? If I change
to a 158x126 mode I've done the lower part of the screen (approx after
16K) contains the test pattern put out in rt_load_mon. My guess is that
a signed short is used where an unsigned should be, but I haven't had
the time to look deep enough to find this.
Another problem I've had is that for some time the Xamiga+retina haven't
worked (the screen get's into a weird mode, it's impossible to reset the
server with the keyboard reset sequence, and ktracing it will not sync
the ktrace.out to disk thus making it impossible for me to see where).
As I don't use X, I don't know when this started for me. Do someone else
still run Xamiga+retina?