P96 and cybervision 64/3d(phase5) and bvision

[Karlos]

@JJ

P96 and CGX are just slightly different solutions to the same problem. P96 is free (afaik), which can be a deciding factor for many. I had to pay 20UKP for cgx v4 for my Bvision.

I've heard a lot of bad things about CGX on older cards like the CV64, corrupted graphics etc. I have to confess, I never had any problems on my BVision with it.

An advantage of p96 is that it emulates a fairly decent chunk of the CGX API, so a lot of stuff written originally for CGX should work.

P96 has drivers for most of the original amiga graphics cards, including the CV64/3D. I believe unofficial p96 drivers exist for Bvision/Cvision also...

A PPC version of p96 is indeed under development, but won't be much use to you unless youre using OS4 ;-)

[Karlos]

OS4 does have a driver system for supporting lots of chipsets on the A1 etc.
P96 is used for its API (also for support of "classic" amiga cards) so that existing RTG software runs OK.

A PPC version for OS3.9 makes very little sense. A fast 68060 already maxes out existing gfx busses for transferring data into VRAM (which is generally the most time consuming part of these systems). Hence the PPC wouldn't gain much on those operations.

Since most other on-card 2D operations are HW accelerated on the blitter, calling them via Warpos PPC interface would only slow things down due to context switching.

However, offscreen rendering in fast ram using the PPC might be an idea for OS3.9/p96, but it only makes sense for fairly large operations that would take more time on 680x0 alone than a typical context switch does under warpos.

[Karlos]

NightShade737 wrote:
What do you mean by "context switching"?

Oh, P96 isn't free btw, it's Shareware.

Context switching occurs calling the PowerPC processor from the 680x0 one (or vice versa). Calling one CPU from the other involves flushing the caches of both - up to 8K for a 68060 and 32K for a 604. Hence a context switch is an extremely expensive operation. You have to do this when bothe CPUs are talking to the same area of memory in copyback cache mode, because if you dont, there is no guarentee that the two different CPU's caches are in sync.


A PPC p96 makes sense only for

1) A PPC native amigaos in general

2) A seperate driver system for WarpOS (a bit like the way warp3D works with seperate drivers for 68K and PPC)

3) Accelerating offscreen rendering on bitmaps in fast ram. This would involve writing some ppc code to do the normal graphics.library style rendering in these cases

(1) is in progress

(2) is unlikely to be worth the effort since (1) is in progress

(3) is a possibility if you are an experienced coder willing to try and make a suitable patch.


As for the ppc version of cybergraphx for OS3.x. This contained *no* ppc code of any kind. The only difference was that it used the 680x0 side of the ppc.library to allocate memory with 32 byte alignment to satisfy the PowerPC's cache alignment.