On 2020-05-11 10:51 p.m., Alex Deucher wrote: > On Mon, May 11, 2020 at 4:25 PM Rui Salvaterra <rsalvaterra@xxxxxxxxx> wrote: >> A segunda, 11/05/2020, 21:21, Alex Deucher <alexdeucher@xxxxxxxxx> escreveu: >>> >>> Note there is no loss of functionality here, at least on radeon >>> hardware. It just comes down to which MMU gets used for access to >>> system memory, the AGP MMU on the chipset or the MMU built into the >>> GPU. On powerpc hardware, AGP has been particularly unstable, and >>> IIRC, AGP has been disabled by default on radeon on powerpc for a >>> while. >> >> So this basically just drops support for the AGP GART? What happens to the AGP signalling rates (beyond the base rate)? > > I don't remember enough of the details, but I strongly doubt it was > related to which MMU was used per se. On r1xx/r2xx parts, AGP was > effectively the non-snooped route to memory and the internal MMU only > provided snooped (coherent) access to memory. That and the limited > TLB space are probably want limited performance in that case. I don't > recall what sort of TLBs the chipset GART tables provided. On r3xx > and newer the, on-chip MMU supported both snooped and unsnooped > transactions and had more TLB space so the difference wasn't > significant IIRC. FWIW, on my last-generation PowerBook with RV350 (IIRC), there was a big performance difference between AGP and PCI GART. The latter was sort of usable for normal desktop operation, but not so much for OpenGL apps (which were usable with AGP). -- Earthling Michel Dänzer | https://redhat.com Libre software enthusiast | Mesa and X developer _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
