I am trying to overclock my A3640 for the shear fun of it but I am not having much luck.

I replaced all capacitors on the card and socketed the oscillator.  

I also did the delay line modification as described here: http://members.iinet.net.au/~davem2/overclock/a3640.html

Card works great @ stock 25mhz with both XC68040-25 & XC68040-40 cpus that I tried but won't boot at either 30mhz or 33mhz as is mentioned should be attainable.  

Actually it did boot ONCE at 30mhz but hung-up early on.

A3640 is ver. 3.1 which I am thinking may be the problem.  

Any ideas?

Seems the A3000 motherboard isn't designed with signal integrity in mind. But what causes it specificly?

Yes, I am installing this in an A3000.

I am not sure what speed my zips are but I will check tonight.  I have the A3000 filled with the full 16mb of zips.

I was hoping to at least get this up to 30mhz.  I am planning to heatsink the gal chips and heatsink/fan the '040.

Thanks for the input all!

Faster ZIPs
Or a SIMM adapter that connect to sockets.

70 ns seems to enable 14 MHz..

Using static column ZIPs (xxxx02) with an '030 is a bit faster for enabling its burst mode. The '040 burst mode is not supported by Ramsey anyway, so you can use fast page ZIPs or SIMMs as well (SIMMs are always FP).

With very fast SIMMs (<60 ns) you could try setting Ramsey to 16 MHz (J851 to 1-2), removing a memory wait state. This would really speed up things, esp. with an '040 - but I've never tried it. Anyone?

It's not signal integrity limiting the A3000 mobo it's SuperDMAC. Remember, the A4000 does not have one, it has IDE PIO logic instead.

80 ns memory should be fast enough to run RAMSEY @ 30 MHz (the A3000/4000 custom chips were actually designed to run @ 28 MHz and under-clocked to 25 MHz for production reasons and because Motorola would not guarantee performance on over-clocked 25 MHz CPU's. With 70 ns memory you could run RAMSEY @ 33 MHz on an A4000.

You still need to check the mobo +5V and if you installed the new caps with correct polarity. Also, what versions of RAMSEY and SuperDMAC are installed?

Erm.... no. The custom chips always need to run on 28 MHz or you wouldn't get anywhere near NTSC/PAL frequencies. The Amiga has two distinct busses that may be run asynchronously.

No. It's the only the graphics chips (FAT AGNUS and ALICE)    which use a master clock of 28 MHz. This master clock gets divided down to 7 and 3.5 MHz for ECS systems (DENISE) and 14/7 and 3.5 MHz for AGA systems. (LISA).

RAMSEY, SUPER BUSTER, FAT GARY and SUPER DMAC are 030 bus protocol chips which run synchronous to the CPU and I quoted Dave Haynie on them being tested @ 28 MHz.

>Perhaps it doesn't like to run on anything other than 25MHz. "Well, overclocking the A3000 motherboard isn't recommended, though I did most of my Buster simulations at 28MHz, just because our testers didn't support multiple asynchronous clocks, so I had to run at 28MHz to get the 7MHz timing correct."

Dave Haynie

I have checked the polarity of all caps on the A3640 and they are all correct.  BTW, they were all just replaced.  

Also checked the +5v on the A3640 @ the caps and it is 5.02v.

The A3000 MB chips are as follows:
Ramsey is -4
SuperBuster -11
SuperDMAC -02
WD -08 (chip was just upgraded from -04)

CPU is XC68040-40 and has a heat-sink and fan.  The GAL's on the A3640 are also heat-sinked.

No zorro cards installed for test, only a CF card through a ACARD scsi-ide and ide-cf adapter.

Still boots fine @25mhz (w/ 50.0 crystal)  but no go with a 60.0 crystal oscillator.

I'm thinking this A3640 just can't do it.