Path: utzoo!utgpu!watmath!isishq!f171.n221.z1.FIDONET.ORG!izot From: izot@f171.n221.z1.FIDONET.ORG (Geoffrey Welsh) Newsgroups: comp.sys.cbm Subject: Re: C128,C128D, and C128C??? Questions Message-ID: <1935.2432C063@isishq.FIDONET.ORG> Date: 27 Mar 89 20:14:45 GMT Sender: ufgate@isishq.FIDONET.ORG (newsout1.25) Organization: FidoNet node 1:221/171 - Izot's Swamp, Kitchener ON Lines: 81 > From: elg@killer.Dallas.TX.US (Eric Green) > Message-ID: <7664@killer.Dallas.TX.US> > is not excessive overhead. Besides, the Commodore disk routines work > via voodoo and glue, and have been so hacked over the years that I > doubt you could implement them on another processor without special > hardware (e.g. a 6526's serial register to clock data in & out). Let's not forget that the Z80 does have full access to the I/O chips. > For modem and screen i/o, though, the overhead of the processor-switch > is way too slow. Especially for modem i/o. I have to agree with you there. While writing my fast RS-232 drivers, one of the key matters was interrupt reaction time. Processor switching would add too much to that. > I love the 6809. Ever since I bought a surplus 6809 book from a > defunct SuperPet dealer, I've wanted to put together something that > used one. I'd actually like to throw a very fast 6809-based system myself. Nothing designed to topple the current 386 or workstation market, mind you, just something to impress on people the power of 8-bit systems. I'd want to include a DMA processor and an ST-412 interface for hard drive(s), perhaps half a meg of RAM (bank-switched), OS/9 operating system? > With a 4-color screen there is no hardware reason for slow scrolling, > though. Two 16-K blits should occur almost instantaneously. There is "should", and there is "does". > The main > reason for slow scrolling in commercial terminal programs is that I > have never seen a commercial terminal program worth a bucket of warm > spit -- whether for Amiga, C-64, C-128, or whathaveyou. Most Amiga > term programs use the console.device for their terminal output, which > does NOT seem to be particularly speedy. That's more or less what we told Commodore Canada when we showed them DesTerm 128 and said we wanted developer status because we were thinking of doing something similar for the Amiga. They accepted our application quickly (I guess we weren't just a couple of clowns, we were a couple of clowns with some impressive software). I'll bet that, if you saw DesTerm running 16-colour ANSI at 9600 bps, you would at least reconsider the "... worth a bucket of warm spit" phrase. > I might note that the VDC in the C-128 only has to block-move a whole > 2K of RAM to scroll the screen. Because all of Matt's screen stuff is done through generic windowing routines, lines are moved one at a time. > I suspect the VDC would have no > trouble keeping up with 19,200 baud or even 32kbaud -- although the > rest of the computer probably would get pretty stressed out at 32kbaud > (my brother says 19.2kbaud with a real ACIA sucks up about half the > CPU power of a stock C-64, so I guess 32kbaud would do the same for > the 128). If I was going to build a terminal... the VDC is such a > natural for such an application, it's a shame that Commodore will > never release it onto the consumer marketplace. I did some experiments with software RS-232 drivers at high speeds. While 19,200 is definitely attainable without a UART, the code generated occasional errors at 38,400 and that leads me to conclude that a C128 will not soon be running 38,400 without additional hardware. However, my opinion that 19,200 bps is practical in software on a C128 suggests that 9600 should be fairly easy on a C64 without a UART or ACIA. Based on that, I can't help but wonder why 19,200 (twice the speed) would cause problems on a C64 with an ACIA (which reduces overhead by as much as a factor of ten)... -- Geoffrey Welsh - via FidoNet node 1:221/162 UUCP: ...!watmath!isishq!171!izot Internet: izot@f171.n221.z1.FIDONET.ORG