[Virtualacorn-list] MDF for 2560x1440 pixel monitor

[T.O.M.S.]

On Sun Nov 3 13:24:49 GMT 2013 Bruce Goatly bruce at goatly.co.uk 
sayeth:

> The MDF that Alex kindly supplied in March, namely

> # For display in the Windows desktop
> # 2560 x 1440 (51hz)
> startmode
> mode_name:2560x1440
> x_res:2560
> y_res:1440
> pixel_rate:197000
> h_timings:10,10,16,2560,0,0
> v_timings:10,0,0,1440,0,0
> sync_pol:0
> endmode

> works fine on my 27-inch Mac, though at 32k colours rather
> than 16M, and the refresh rate seems to be 52Hz rather
> than the stated 51Hz. But it's excellent for my needs!

Thanks for that Bruce, but did you not find that it was unstable when 
selecting 16M colours with the ARM7500 core emulation - so you 
reverted to using the ARM610 core - hence the 32K colour limit?

I'm a tad nervous about suggesting the ARM610/32K colour combination 
to 'Mr Keen' as (since March) we had the report of someone suffering a 
seriously slow screen refresh rate on his new PC laptop in his 
habitual 32K colour mode, but that setting 16M colours solved it. See 
the blurb on pp54/55 of the VirtualRPC In Use '10 year anniversary 
bumper supplement' on 
http://www.virtualacorn.co.uk/support/vrpcinuse/index.htm  (Sorry 
about the shamless ad...)

So as he's already said he would prefer 16M colours anyway, can anyone 
help please?


On Sun Nov 3 13:41:25 GMT 2013 David J. Ruck druck at druck.org.uk 
sayeth:

> Just reduce the 1600 to 1440, as VRPC will use the PC mode of the
> same resolution, and ignore the actual timing information.

Thanks David. Tried that (albeit on a PC with a resolution limit of 
1920x1200 pixels*) but unfortunately it reverts to the default state 
of 800x600 pixels which cannot be changed. I'm floundering on this but 
I sense the secret is in calculating the appropriate pixel rate - 
which is well beyond my ken.

But for my understanding, are you saying that as the underlying Big 
iMac has a native screen mode of 2560x1440 pixels, then 
VirtualRPC/RISC OS will pick that up, even if the (197000) pixel rate 
in the RISC OS MDF is inappropriate?

* Bearing in mind that mohsen's RISC OS MDF for an enormous 2560x1600 
pixels works fine in 16M colours on the same PC/monitor.)


> You will have to change to using the ARM7500 emulation, as the
> StrongARM one emulates the limitation of 2MB of VRAM of the
> Risc PC.

It's 8MB 'VRAM' for the StrongARM and ARM610 cores on the PC variants 
of VirtualRPC, but again for my understanding, is it only 2MB for the 
Mac variant please?


Many thanks to both for the interesting postings, it all helps we 
non-techies to know how the innards work.

Alex Hamilton
pp T.O.M.S.