>From the examples I've seen /used you can get 50 raster lines of 2MHz operation on NTSC and 100 raster lines on PAL. The trial I did gives 40% speed up on PAL in BASIC, I'm sure that this would help greatly when shift lots of data during screen scrolls in paint/write/calc.... Having thought conceptually a little more about it: 1) you need to find room to install three routines a) modify vector tables to new IRQ (turn on) b) modify vector tables to old IRQ (turn off) c) actual IRQ handler 2) disk I/O vectors need to point to new routines so as to change to 1MHz during disk ops and to ~2Mhz when finished, ie three JRSs and RTS in theory it should be possible for the one program to work on both PAL and NTSC systems (just sets different raster values on startup) question remains where to find the code space for this.... - nick > -----Original Message----- > From: Larry Anderson [SMTP:email@example.com] > Sent: Friday, 12 November 1999 2:07 > To: firstname.lastname@example.org > Subject: Re: 2Mhz Geos64?? > > Cameron Kaiser wrote: > > > > >>Does Geos128 run at 2Mhz when in 40col screen mode or only in 80col? > > > > > >Screen mode doesn't matter. Anything runnning on the C128, in C128 > mode, > > >is running at 2Mhz. > > > > No, no. The VIC-IIe can't do 2MHz and keep the 40-column screen updated. > > Unless the screen is blanked, if you're in 40-columns, you're at 1MHz > (even > > in 128 mode). Only the VDC can continue to do screen updates at 2MHz. > > > But with the application of raster interrupts you could achieve a speed > increase if you can get the processor to do 2 mghz when the video scan is > not > on the visible screen. I recall an article stating it would be about a > 25% > increase... I recall there is a 128 version of Mah Jongg that employs > this technique... > -- > 01000011 01001111 01001101 01001101 01001111 01000100 01001111 01010010 > 01000101 > Larry Anderson - Sysop of Silicon Realms BBS (209) 754-1363 300-2400 > baud > Commodore 8-bit page at: http://www.jps.net/foxnhare/commodore.html > 01000011 01001111 01001101 01010000 01010101 01010100 01000101 01010010 > 01010011 > - > This message was sent through the cbm-hackers mailing list. > To unsubscribe: echo unsubscribe | mail > email@example.com. ------------------------------------------------------------------------------------------------ PLEASE TAKE NOTE: The contents of this email (including any attachments) may be privileged and confidential. Any unauthorised use of the contents is expressly prohibited. If you have received this email in error, please advise us immediately (you can contact us by telephone on +61 8 9441 2311 by reverse charge) and then permanently delete this email together with any attachments. We appreciate your cooperation. Whilst Orbital endeavours to take reasonable care to ensure that this email and any attachments are free from viruses or other defects, Orbital does not represent or warrant that such are free from computer viruses or other defects. (C) 1999: Orbital Engine Company (Australia) Pty Ltd and its affiliates - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail firstname.lastname@example.org.
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