lantz@Apple.COM (Bob Lantz) (12/08/90)
Fabian@cup.portal.com (Fabian Fabe Ramirez) writes: >Steve, >As previously stated, there are NO accelerated video cards whose acceleration >feature is supported by A/UX. PLEASE remember that A/UX is a completely >different OS and thus, the data structures are completely different than the >Mac OS. Although A/UX uses the same data structures as MacOS (indeed, we have 32-bit QuickDraw, etc..) A/UX (and other virtual memory systems for the Mac) pose some problems for NuBus cards which expect to have direct access to the Mac address space. In MacOS your physical addresses and virtual addresses are generally the same (with some exceptions,) whereas in A/UX they are not. Also, you can imagine problems in allowing one user to control a NuBus card which has direct access to the physical memory of the system. >Fabian Ramirez >SuperMac Technology >fabian@cup.portal.com >sun!cup.portal.com!fabian
paul@taniwha.UUCP (Paul Campbell) (12/15/90)
In article <47191@apple.Apple.COM> lantz@Apple.COM (Bob Lantz) writes: > >Although A/UX uses the same data structures as MacOS (indeed, we have 32-bit >QuickDraw, etc..) A/UX (and other virtual memory systems for the Mac) pose >some problems for NuBus cards which expect to have direct access to the Mac >address space. In MacOS your physical addresses and virtual addresses are >generally the same (with some exceptions,) whereas in A/UX they are not. There is only one accelerated video card out there that I know of that does bus accesses to main Mac memory and potentially has problems with VM/AUX - that's the Apple 8*24GC. Other cards DO have problems because A/UX DOES have different data structures from the MacOS for video cards - A/UX splits video drivers half between the kernel (for vertical retrace interrupt handling to load palettes and to move the cursor) and user space (for application drawing etc). I'm not saying it can't be done (it's certainly much easier for us than for Apple :-), the real problem is putting a lot of work into doing this stuff for a pretty small market and running the risk of having Apple change the interface out from under us again (like 1.0->2.0, I think that after 2.0 this will become less of a problem). Paul Campbell Accelerator Architect and A/UX Hacker SuperMac Technologies -- Paul Campbell UUCP: ..!mtxinu!taniwha!paul AppleLink: CAMPBELL.P We three kings of Orient are One on a Tractor One in a Car One on a scooter Tooting his hooter Following yonder star - F. Dagg circa 1972