d89-ahg@sm.luth.se (Anders Hedberg) (10/08/90)
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
geoff@actrix.co.nz (Geoff McCaughan) (10/10/90)
In article <1164@tau.sm.luth.se> d89-ahg@sm.luth.se (Anders Hedberg) writes: > > 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. [stuff deleted] > 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 tried this (7M XOR CDAC), it worked - but only just, I got endless guru's > I divided the E signal by two ( down to normal speed ). Ever stepped the drive E /2 doesn't seem to work. I also tried 7M /10, this worked @ 7MHz, but wouldn't @ 14. Does anyone know if the 6:4 m/s ratio of the E clock is all that important? I also tried (just for something to do) 7M /10 AND E to maintain phase with E, but no go. I put a 4K7 resistor to ground on the CLK pin of the 68000 and a ferrite bead on the wire leading to it, this got me starting up properly more than 80% of the time - sounds weird, but it seems to help, I guess I was getting some ringing. If anyone knows a way to get this thing running 100% I'd like to know about it. BTW when I get my machine running it goes great - very reliable and quite a speedup. My hard drives run fine, and two of my floppies are OK as well (internal 3.5" & external 5.25"), the other one is hopeless unless I run steprate to slow it down, this helps, but it's still not 100% reliable, even if I slow the steprate down to 10* the normal delay, so: is there more going on here than just the head stepping, what else are the timers screwing up? Also of interest, QuarterBack, Xcopy and MSH, all work fine on all my floppies, so it seems that anything that doesn't use trackdisk.device works. Hope to hear from some more of you hardware hackers soon...... keep your iron hot! -- ------------------------------------------------------------------------------- Geoff McCaughan Email: geoff@actrix.co.nz Phone: +64 3 539545 or 852101 Amiga/Hardware/Unix/Quantum Mechanics Hacker Phax : +64 3 539567 "Anarchy: Think of it as evolution in action." ^ NEW ZEALAND!
rooijen@rulcvx.LeidenUniv.nl (A.J. van Rooijen) (10/11/90)
In article <1990Oct9.230639.9336@actrix.co.nz> geoff@actrix.co.nz (Geoff McCaughan) writes: >If anyone knows a way to get this thing running 100% I'd like to >know about it. To make the board work for 100% you must emulate the 7MHz 68000 behaviour of your board for the processor socket. No matter how fast your board is. The best thing to do is to generate the E-clock yourself instead of dividing E-clock signals and take care of the VMA/VPA stuff. Furthermore you have to synchronize the DTACK* and the AS* with the original 7Mhz clock according to the M68000 specifications. In practice this will mean waitstates. All this requires some more components than a simple F logic FlipFlop. We have a prototype running for months now, without a problem, no gurus or something like that. The speed increase is around the 20-25%, however a program containing just DIV's and MULU's will approach 100% (not a realistic situation). I hope this will clear things up around the 14 Mhz hack, which is not so simple afterall. Erwin van Breemen The Orega Programming Group Holland Apothekersdijk 24 Leiden Holland
dzenc@gnu.ai.mit.edu (Dan Zenchelsky) (10/11/90)
In article <994@rulcvx.LeidenUniv.nl> rooijen@rulcvx.LeidenUniv.nl (A.J. van Rooijen) writes: >We have a prototype running for months now, >without a problem, no gurus or something like that. The speed increase is >around the 20-25%, however a program containing just DIV's and MULU's will >approach 100% (not a realistic situation). > >Erwin van Breemen Any chance you could post the schematics? Thanks -Dan -- ___________________________________________________________________________ | _______ |________________________________________| | || |o| Dan Zenchelsky | | | ||____| | | Any sufficiently advanced bug is | | | ___ | dzenc@gnu.ai.mit.edu | indistinguishable from a feature. | | |_|___|_| |______________-- Rich Kulawiec__________| |__________________________________|________________________________________|
billsey@agora.uucp (Bill Seymour) (10/12/90)
In article <1990Oct9.230639.9336@actrix.co.nz> geoff@actrix.co.nz (Geoff McCaughan) writes:
:
:BTW when I get my machine running it goes great - very reliable and
:quite a speedup. My hard drives run fine, and two of my floppies are
:OK as well (internal 3.5" & external 5.25"), the other one is
:hopeless unless I run steprate to slow it down, this helps, but it's
:still not 100% reliable, even if I slow the steprate down to 10* the
:normal delay, so: is there more going on here than just the head
:stepping, what else are the timers screwing up?
The big problem (and the one you can't easily fix in software)
is the settle delay after the drive motor starts. It waits 'x' length
of time after power up before allowing a read or write of the disk.
That allows the drive to come to full speed before any bits get read
or written. If you don't allow for quite enough time there, you run the
risk of writing data at the wrong rate.
:Also of interest, QuarterBack, Xcopy and MSH, all work fine on all
:my floppies, so it seems that anything that doesn't use
:trackdisk.device works.
:
:Hope to hear from some more of you hardware hackers soon...... keep
:your iron hot!
:
:-------------------------------------------------------------------------------
:Geoff McCaughan Email: geoff@actrix.co.nz Phone: +64 3 539545 or 852101
:Amiga/Hardware/Unix/Quantum Mechanics Hacker Phax : +64 3 539567
:"Anarchy: Think of it as evolution in action." ^ NEW ZEALAND!
--
-Bill Seymour billsey@agora
***** American People/Link Amiga Zone Hardware Specialist NES*BILL *****
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