[Virtualacorn-list] MDF for 2560x1440 pixel monitor

[T.O.M.S.]

Hello again folks

Many thanks to all of you for your helpful inputs. As a result, we've
been in trial-and-error mode for the last couple of hours and *may*
have sussed out a working solution.


On Sun Nov 3 17:35:15 GMT 2013 David Pitt pittdj at pittdj.co.uk
sayeth:

> I have just tried the 2560x1440 mode above in 16M colours on
> my 1920x1200 iMac and though it did seem display OK but
> VRPC was not entirely stable with it when in full screen mode
> giving errors like "abort on instruction fetch at &00000090".

Understood, that rings a bell.  So question for Bruce G: Do David's
observations tie in at all with the comments you made last March, when
you said:

> I'm finding the ARM7500 model too unstable ...  - things keep
> falling over...

and which caused you to reduce the colour depth to 32K, when it all
came good?

If so, I sense the problem *may* be that the screen memory in 16M
colours is close to the ARM7500 core emulation limit (thought to be
16MB) and which may be triggering the hiccups. But who knows? I
certainly don't...


Anyway, in accordance with Good Old Yorkshire trial-and-error, we've
taken the MDF which Bruce G suggested earlier, and 'scaled down' the
pixel_rate to 192600 (was 197000) to cater for the fewer pixels being
displayed. So the test MDF now reads:

# For display in the Windows desktop
# 2560 x 1440 (51hz)
startmode
mode_name:2560x1440
x_res:2560
y_res:1440
pixel_rate:192600
h_timings:10,10,16,2560,0,0
v_timings:10,0,0,1440,0,0
sync_pol:0
endmode

We've tried this on 3 of our 1920x1200 pixel monitors - with the
ARM7500 core emulation and 16M colours selected - and it seems to be
running fine in 16M colours, with no evident instability.   :-)

Screen memory comes out at 14400K, so there's a reasonable buffer
before hitting the 16MB stops.

The pixels aren't entirely square, but my understanding is that's to
be expected if we're emulating a 1:1.77 aspect ratio screen mode on a
physical 1:1.6 display.

So, please, would any or all of you like to try this MDF on your
monitor(s)? Does it give a stable, full-screen display in 2560x1440
pixels? Does it give you 16M colours or does it drop to 32K? What's
the screen memory used? Any other business? Are we there yet?

TIA folks, regards

Alex Hamilton
pp T.O.M.S.