ianr@mullian.ee.mu.OZ.AU (Ian ROWLANDS) (01/18/91)
Since I got my bridgeboard, I've noticed that the display is rather slow when displaying graphics. This occurs even with the window having a priority of 10, and no other processes running. Has anybody else noticed this? Also, how does the display perform with an accelerator in the system (the Amiga side, I mean)? Does the speed pick up or is the display still slow? Ian Ian Rowlands | Uni : ianr@ee.mu.oz.au Dept. of Electrical Engineering, | OR ..!uunet!mullian.ee.mu.oz.au!ianr (including Computer Science) | Home : ianr@gpark.pub.uu.oz.au University of Melbourne | OR ..!uunet!gpark.pub.uu.oz.au!ianr
iheitla@cs.vu.nl (Ilja Heitlager) (01/18/91)
Ian Rowlands said : > Since I got my bridgeboard, I've noticed that the display is rather > slow when displaying graphics. This occurs even with the window having a > priority of 10, and no other processes running. Has anybody else noticed this? > Also, how does the display perform with an accelerator in the system (the Amiga > side, I mean)? Does the speed pick up or is the display still slow? > Yes I got a commodore XT-card running with a Herculesvideo card. Both the Hercules and the Ami-window can monitor the same output. Then you can see that the window is indeed slower. I have no answer nor a solution for this. Sorry it is just happening BTW somehow it aint fair, a m68k running as a I/O processor for a Intel8088. (But life goes on. sigh) Ilja Heitlager Vrije Universiteit Amsterdam The Netherlands <iheitla@cs.vu.nl>
peterk@cbmger.UUCP (Peter Kittel GERMANY) (01/19/91)
In article <6474@munnari.oz.au> ianr@mullian.ee.mu.OZ.AU (Ian ROWLANDS) writes: > > Since I got my bridgeboard, I've noticed that the display is rather >slow when displaying graphics. This occurs even with the window having a >priority of 10, and no other processes running. Yes, that can't be avoided since there is really some overhead. When the PC (or AT) side writes something into its video RAM area, that occurs with full speed and appears immediately on the Amiga side in the dual-ported RAM. But this is NOT the Amiga display RAM! So there is a circuitry that detects every change in this RAM area and causes an interrupt for the Amiga CPU. In that interrupt routine the Amiga copies the changed data to the appropriate bitmaps in its Chip memory, so that it becomes visible. So there is a delay until a change appears visible on the Amiga screen, but the overall performance of the PC side is NOT affected. (This can turn into a disadvantage when an A2286 scrolls a DIR so fast that you lose most of it when viewing it in an Amiga window...) >Also, how does the display perform with an accelerator in the system (the Amiga >side, I mean)? Does the speed pick up or is the display still slow? Yes, this helps, as the CPU can do the above mentioned things faster. But you can never achieve the speed of a simple PC-side pure-text display. -- Best regards, Dr. Peter Kittel // E-Mail to \\ Only my personal opinions... Commodore Frankfurt, Germany \X/ {uunet|pyramid|rutgers}!cbmvax!cbmger!peterk
andrew@teslab.lab.OZ (Andrew Phillips) (01/22/91)
In article <6474@munnari.oz.au> ianr@mullian.ee.mu.OZ.AU (Ian ROWLANDS) writes: > Since I got my bridgeboard, I've noticed that the display is rather >slow when displaying graphics. This occurs even with the window >having a priority of 10, and no other processes running. Has anybody >else noticed this? Yes, this is due to the fact that a task on the 68000 side has to read the dual port RAM and write to the bit planes of the MSDOS window. This causes the only compatibility problem I have noticed with my SideCar, which is not being able to run some games which update the screen continually (not that MSDOS games are worth playing). The effect can be lessenned somewhat by using less colours in the MSDOS window, thus reducing the number of bit planes that the task has to write to. Actually I find it surprising that it is as fast as it is considering its done in software (with a bit of hardware help to avoid bit fiddling). This speed limitation is probably why there has never been EGA emulation for SideCar/BridgeBoard. >Also, how does the display perform with an accelerator in the system >(the Amiga side, I mean)? Does the speed pick up or is the display >still slow? An Amiga accelerator would improve it somewhat but probably the greatest limiting factor is the speed of writing to CHIP RAM. Of course, having an accelerator on the MSDOS side (such as a 386 card) would not improve the display update speed at all. Andrew. -- Andrew Phillips (andrew@teslab.lab.oz.au) Phone +61 (Aust) 2 (Sydney) 289 8712