Vesa 2 LFB vs Banking

[pikasoo]

Hi,

I would like to know if some of you tested the real performance of both ...

from what i could read on diferent website, the speed was'nt always listed as a diference between lfb and banking.

i tested both on 3 emulator, bosch and microsoft virtual pc didnt realy got faster but virtualbox went on the speed, prety much 4 or 5 time faster (ex doom game went from normal fps to impossible to play) as if the emulator forgot any timing for the PIC
(btw i use the PIC for now to produce a tickcount so doom should of keep the normal fps)

so im wondering, on a real hardware, what should be the real advantage of using LFB ???

i guess that banking slow you down when you change the bank but does it realy make a huge diference?

[Brendan]

Hi,

i guess that banking slow you down when you change the bank but does it realy make a huge diference?

Just wait until you're stuck with a 24-bpp mode and realise that one third of a pixel is in one bank and the remaining 2 thirds of the pixel are in a different bank...


Cheers,

Brendan

[pikasoo]

Just wait until you're stuck with a 24-bpp mode and realise that one third of a pixel is in one bank and the remaining 2 thirds of the pixel are in a different bank...

It's true that 24bpp require more code specially in bank mode

[Love4Boobies]

I would like to know if some of you tested the real performance of both ...

Performance depends on the hardware. There is no such thing as a general performance estimate.

i tested both on 3 emulator, bosch and microsoft virtual pc didnt realy got faster but virtualbox went on the speed, prety much 4 or 5 time faster (ex doom game went from normal fps to impossible to play) as if the emulator forgot any timing for the PIC

The timer is irrelevant as far as your problem goes so why even mention it? The game is also unplayable using a remote desktop and a slow connection or when using a computer that is 25 years old but those are also not the cause of your problem.

(btw i use the PIC for now to produce a tickcount so doom should of keep the normal fps)

Don't confuse the PIC and the PIT. They are two very different animals. The former manages interrupts while the latter is a counter.

so im wondering, on a real hardware, what should be the real advantage of using LFB ???

i guess that banking slow you down when you change the bank but does it realy make a huge diference?

It does make a difference because, in the case of bank switching, you sometimes waste some time mapping pages and performing address calculations. The fact that switching from one area of the screen to another requires a switch makes real-time rendering less predictable. Also, since banks may overlap, you may need to use mechanism to decide which bank to use (something like a scheduling algorithm or a preemptive hint or something).

Just wait until you're stuck with a 24-bpp mode and realise that one third of a pixel is in one bank and the remaining 2 thirds of the pixel are in a different bank...

It's true that 24bpp require more code specially in bank mode

That's not at all what he meant. Higher depths don't imply more code. It's just that it's not elegant to plot part of a pixel and then correct it after the switching is complete. However, for banks that overlap, that's not as much of a problem...