> If you're still seeing bad performance it may be because you need to > fix up the MTRR or GART settings. I've done this dance and have no > memory at this point of what you do, but vague memory is that proper > MTRR settings with a good PCIe card will give you far better bandwidth > than the old AGP cards. There is nothing like the 60x assymetry.
i don't think this is the case. if you recall from the original post, i have used the pat registers to set up memory types on a pcie card and i do see dramatic speedups for drawing to the screen. however, reading from the screen is just as slow as before. according to the intel's x86 arch guide vol 3a, §10-8, p. 466 speculative reads are allowed for WC/WT/WB memory. so i wouldn't think that it's a bus problem at all. if you recall, the only difficulty in using subpixel fonts a few years ago was the fact that for hold mode and deselection, the the α draw was done with the new mask and the on-screen image, which was read from the frame buffer. not only did this result in a squared α, it was also sloooow, especially on nvidia cards. oddly, the via machines driven in vesa mode were the fastest. the speed up was at least a factor of 10; you could easily see the speedup. at this point, you probablly don't believe me. so maybe some numbers will help make the case: ; time dd -if /dev/wsys/1/screen -of /dev/null -bs 512k 0+1201 records in 0+1201 records out 0.00u 0.03s 4.04r dd -if /dev/wsys/1/screen -of /dev/null ... ; time dd -if /dev/zero -of /dev/null -bs 512k -count 1201 1201+0 records in 1201+0 records out 0.00u 0.14s 0.14r dd -if /dev/zero -of /dev/null ... i've seen the same behavior on a number of different nvidia cards of different generations. newer cards seem to be worse than older cards. (if you have the programming interface manuals, i'd be happy to double-check the settings. ☺.) can you explain what the downside of double-buffering would be? it's not like the days where we asked, hey buddy, have you got 4 megs to spare? - erik
