barnhill@kuhub.cc.ukans.edu (06/12/91)
I understand that there was a posting somewhere about speeding up a IIsi by setting the RAM cache at a fairly high level, and wonder if anyone would be so kind as to fill me in? Thanks db Dave Barnhill Barnhill@kuhub.cc.ukans.edu
ejb@think.com (Erik Bailey) (06/12/91)
In article <1991Jun11.161138.31376@kuhub.cc.ukans.edu> barnhill@kuhub.cc.ukans.edu writes: > I understand that there was a posting somewhere about speeding up >a IIsi by setting the RAM cache at a fairly high level, and wonder if anyone >would be so kind as to fill me in? > Thanks > > db >Dave Barnhill >Barnhill@kuhub.cc.ukans.edu I'd be happy to. The trick is to set the RAM Cache to 768k [*]. In 256-color mode, the IIsi reserves 256k for video RAM. The high (or low, whichever it is) 1MB of RAM (where the video is) is, for some reason, slow. When code is loaded into that memory bank, such as the Finder, a program, whatever, the speed slows down. However, the disk cache just happens to use that memory. 1MB - 256K = 768k, so that is the setting you should use. While I have not benchmarked the speed improvement, it is enough that I now leave my IIsi in 256-color mode in System 7, whereas it used to be in 16-color mode in System 6.0.7. Good luck! --Erik [*] It has been suggested that 384k may work almost as well as 768k, and save you 384k in the process. I have not tried this; your mileage may vary. -- Erik Bailey | 7 Oak Knoll | Thinking Machines Corp. ejb@think.com | Arlington, MA 02174 | 245 First St. harvard!think!ejb | (617) 643-0732 | Cambridge, MA 02142 /earth is 98% full. Please remove any excess inhabitants.
johns@hpcuhe.cup.hp.com (John Shelton) (06/13/91)
> In 256-color mode, the IIsi reserves 256k for video RAM. The high (or low, > whichever it is) 1MB of RAM (where the video is) is, for some reason, slow. > When code is loaded into that memory bank, such as the Finder, a program, > whatever, the speed slows down. > > However, the disk cache just happens to use that memory. 1MB - 256K = 768k, > so that is the setting you should use. While I have not benchmarked the > speed improvement, it is enough that I now leave my IIsi in 256-color mode > in System 7, whereas it used to be in 16-color mode in System 6.0.7. > > Good luck! --Erik So why is 256-color mode slower than 16-color mode, then? It seems that 16-color mode would reserve less memory, making it more likely that you program would be running out of the slow memory. - John
rosen@cs.utexas.edu (Eric Carl Rosen) (06/14/91)
>So why is 256-color mode slower than 16-color mode, then? It seems that >16-color mode would reserve less memory, making it more likely that you >program would be running out of the slow memory. Probably becase in 16-color mode, redrawing the screen takes less time than in 256-color mode since less memory needs to be written. In 16-color mode, 640x480 pixels x 4 bits/pixels = 150 KB. In 256-color mode, 640x480 pixels x 8 bits/pixels = 300 KB. If all things were equal (which they aren't, I imagine, since dealing with full bytes is more efficient than half-bytes), you would thus expect redrawing a 16-color screen to take half the time that redrawing a 256-color screen would require. So, apparently the slowdown experienced from drawing in 256-color mode is more than offset by running your program out of the faster RAM above 1 MB. --Eric