Subject: Re: bankeddev for Retina?
To: None <>
From: Niklas Hallqvist <>
List: amiga-x
Date: 09/22/1994 23:04:52
>>>>> "Markus W" == mw  <> writes:

>> 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.

Markus W> I don't think -even if this approach would work- it's even
Markus W> worth the effort thinking about it. There are PC servers
Markus W> (XFree comes to mind) that are specifically built and
Markus W> optimized to deal with VGA chips that use banked
Markus W> addressing. I even think the retina server from our french
Markus W> friends was built from such a PC server. It would make much
Markus W> more sense to get such a server running on RetinaZ2, instead
Markus W> of going all the way to make kernel-level bank-switching
Markus W> sort of efficient...

Yeah, I guess you're right.  But I thought it would be neat to have
a hardware-independent server, just like Chris thought once...
Maybe the grf* devices could be extended to deal with banked
systems so they all could have an ioctl set for dealing with
banking.  Then add a flag to struct grfinfo stating what interface
(i.e. banked or flat) this grf uses.  Still just an idea, not a
volunteering statement.  I have recently committed myself to get
AmigaMach back in shape again (after the isa project is finished).

>> 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.

Markus W> I think to remember that the chips text mode only works in
Markus W> certain display modes (due to increased bus load in this
Markus W> mode compared to the corresponding graphics mode). I think
Markus W> it's for example not possible to run text mode at anything
Markus W> larger than 1024x768.

Possible, but from what I've seen, I don't think it's exactly 1024x768.
It really seems to be 16K chars which would mean 1176*888 or something.
I'll test this at home.

Another related topic.  I inverted color 0 and 1 in grf_rt.c, but to
my astonishment I got light borders around my dark background.  Why?

>> Another problem I've had is that for some time the Xamiga+retina
>> haven't

Markus W> That's the french server, right?

Well based on it, I think.