jim@coplex.UUCP (Jim Sewell) (03/10/88)
Here is a technical question to follow the purpose of this group. I and a friend have decided that my 68000 is not working hard enough. Our goal is to make it run at a higher clock speed. The method of attack is to pull the clock signal pin out of the socket, route that thru a separate, faster crystal, and let it run independently of the system speed. We have only tried a 13 mhz crystal which we thought would surely be too fast. It didn't work, but we can not decide if it is our method or just that it is too doggone fast. Questions: Is it possible to speed up the cpu? Will it affect overall system performance (in particular video sync signals and all.) Will our method work? Do you have any suggestions for alternate methods? Any help would be appreciated. Experiments are so much fun! Besides, our Amiga club would be VERY interested in any positive results we would have. ------------------------------------------------------------------------------ "May we all break free of our inhibitions _____ ____ ___ mit-eddie! and enjoy mutual respect, peace, and love / / <___ bloom-beacon! in the world!" // Amiga is awesome / <____ ____> coplex!jim \X/ personified! \__/ J.C. Sewell
avery@puff.cs.wisc.edu (Aaron Avery) (03/11/88)
Well, first of all, to run the processor at a faster clock rate, you need to
get a processor which can go faster! The 68000 in the Amiga can only support
8 MHz. You would have to get a 12MHz 68000 or 68010, or a 16MHz 68010.
Now, the amiga's memory interface with the 68000 slot will not operate any
faster than it does now, as it's basically a synchronous interface. To support
any real speed increase, you need to supply the faster processor with a memory
interface which it can access at the higher clock rate. So, to do what you
wish, you probably want to design a 68010 processor board running at a
higher clock rate, supply it some memory (however much you wish), understanding
that it will only function much faster out of this memory, and allow it to
access the Amiga's memory. If you wish to pursue this further, you may want
to contact Motorola, as they are very good about supplying examples of things
like memory interfacing to a 68010 processor. Good luck!
Aaron Avery (avery@puff.cs.wisc.edu)
({seismo,caip,allegra,harvard,ihnp4}!uwvax!puff!avery)cmcmanis%pepper@Sun.COM (Chuck McManis) (03/11/88)
In article <386@coplex.UUCP> jim@coplex.UUCP (Jim Sewell) writes: >Any help would be appreciated. Experiments are so much fun! Besides, our >Amiga club would be VERY interested in any positive results we would have. Jim, the *first* thing you folks should do is spring for a copy of the schematics of the machine in question. Perusal of the clock circuit in those will show that on the video connector are two lines, XCLK, and XCLKENABLE*. Basically, when XCLKENABLE* is grounded your Amiga is running from the clock coming in on the XCLK pin. You can move the frequency around on this pin to your hearts delight and change the speed of your system. Note that the frequency on this pin should be 8*3.58Mhz or about 28Mhz. Things to note : a) The video is generated from this clock so you had better have a multisync attached to your machine or you won't be able to see the video. b) The time blocks are in the Custom chips and they will crap out at about 30 Mhz. --Chuck McManis uucp: {anywhere}!sun!cmcmanis BIX: cmcmanis ARPAnet: cmcmanis@sun.com These opinions are my own and no one elses, but you knew that didn't you.
yann@ai.toronto.edu (Yann le Cun) (03/15/88)
In article <386@coplex.UUCP> jim@coplex.UUCP (Jim Sewell) writes: >Our goal is to make it run at a higher clock speed. Somebody here at our local Amiga Developper Forum in Toronto did a hack like this. He uses a 16MHz clock, but as far as i understand, he has to switch it back (at the right time) to 8MHz to access the chip memory and the coprocessors. This switching is done on the fly, it seems to work, he has a nice little green/red light on the front of the machine which changes color when the processor changes speed. It seems MUCH more complicated than just connecting the clock pin of the 68000 to a faster clock. The name of the guy is Earl Pottinger. He has done a few other hardware hacks like an el cheapo memory expansion made by stacking the memory chips and soldering their pins together.... it seems to work... Yann le Cun yann@ai.toronto.edu, yann@ai.toronto.cdn AI Group, Dept of Computer Science yann%ai.toronto.edu@relay.cs.net University of Toronto, Canada M5S 1A4 {uunet,watmath}!ai.toronto.edu!yann