Path: utzoo!attcan!uunet!snorkelwacker!bloom-beacon!eru!hagbard!luth!d89-ahg
From: d89-ahg@sm.luth.se (Anders Hedberg)
Newsgroups: comp.sys.amiga.hardware
Subject: 14Mhz Comments
Message-ID: <1164@tau.sm.luth.se>
Date: 8 Oct 90 14:54:49 GMT
Distribution: comp
Organization: University of Lulea, Sweden
Lines: 83


Yes, I've got hold of a 16Mhz 68000 and put it in my Amiga 500 rev 5.??.
It worked fine.
I've got hold of a 74F?? that i divided the 28Mhz agnus frequency down to
14Mhz. It did'nt work fine. Problems: The 68000 needs to be in the right phase
compared to the agnus chip, else you will see 10 short and one long flash on
the powerled. Half the times I started my A500 this happend.
Well, when the powerled didn't flash, I sometimes got the Workbench screen,
asking for a disk. I managed to run a "Mega-demo" that used it's own loading
routine. When booting the workbenchdisk I soon got a disk-unreadable error.
I had a too slow drive, the drive coudn't move the head at the speed the A500
told it to. ( Yes, it did read and runned the bootblock, track 0 )
To get rid of the wrong phase problem, I've removed the 28/2 divider and
installed a 7M XOR ( some other signal ) and got 14Mhz. It worked, but the
drive didn't.
I divided the E signal by two ( down to normal speed ). Ever stepped the drive
by pressing a key on the keyboard and see two chars printed on screen ? No? Try
this :-)  I removed it.
I also tried a programmable 14/7 switch but couldn't get the phase correct when
switching...










(Sorry,

Finnally with a friends faster drive and one XOR and one 68000 a' 16Mhz it
worked.

Now my amiga runs at 7 Mhz, cause what I ended up with was a system that
runned 16-17% faster, refused to work with my A590 ( 1 meg fast) and I couldn't
trust my amiga ie will it brea









Sorry, the terminal doesnt like me, or is it the local computer ???)


































To maybee be continued on another terminal... d89-ahg sm.luth.se