mpierce@ewu.UUCP (Mathew W. Pierce) (11/17/90)
I just Dloaded the 14MHz speedup file by Leslie Ayling(s?) and was wondering
whether or not it will work for the A2000? It is supposedly meant for the
A500, but she says that it will work on other machines.
Isa this a smart thing to do even if you do it right?
System info: A2000 Rev 6.2
3 megs mem.
SyQuest 44 mb HD
Any help would be appreciated.
Matt Piercejeh@sisd.kodak.com (Ed Hanway) (11/17/90)
In article <1344@ewu.UUCP> mpierce@ewu.UUCP (Mathew W. Pierce) writes: >I just Dloaded the 14MHz speedup file by Leslie Ayling(s?) and was wondering >whether or not it will work for the A2000? It is supposedly meant for the >A500, but she says that it will work on other machines. I've seen this speedup "design" and I'd be surprised if it works on _any_ machine. [For anyone who hasn't seen the design, it runs the 28MHz clock through a a D flip-flop configured as a divide-by-2 and runs the resulting 14MHz clock into the bent-up clock pin of the 68000 instead of 7MHz. That's it.] A few weeks ago Dave Haynie posted a comprehensive description of why this has little chance of working, and it boiled down to: 1) Any accellerator must access normal Amiga RAM, ROM, custom chips, expansion devices, etc., with the same timing as a 7MHz 68000, synchronized with the master 7M clock. 2) The 8520 Peripher Interface Adapter chips use the M6800 (yes, 68-hundred) interface, which requires a 0.7MHz E clock, and VMA and VPA signals synchronized to it. There are other problems with this particular design that diminish what little faith I have in it: 1) It refers to the MC68000P12A as a 16-MHz part. My Motorola data books say this should be a 12.5 MHz part. (It has a fair chance of running at 14.3MHz, if you're lucky.) 2) The schematic diagram includes a switch on the clock signal to switch between 14MHz and 7MHz. Now assuming that the switch is mounted so it sticks out of the case, what we have here is a (relatively) long, unshielded wire carrying a high-frequency signal. We EE's have a technical term for this -- it's called an antenna. :-) The amount of RFI that it must generate and/or pick up must be incredible. 3) It mentions something about floppy drives stepping too fast, so the author replaced his with one with that can handle a 5ms track-to-track step rate. I thought that the normal Amiga step rate was about 3.6 ms, and any 3.5" drive should be able to handle 3ms. >Isa this a smart thing to do even if you do it right? As you might guess, I think that to "do it right" you should start with a better design. -- Ed Hanway --- uunet!sisd!jeh Use other side for additional listings. Some assembly required. Any resemblance to real persons, living or dead, is purely coincidental.