Apollo 1240 configuration

[Snoopy1234]

I have here an Apollo 1240 40mhz accelerator. Early model with an XC..M cpu and MACH130-15JC ic. I haven't been able to make it run on my A1200. It's had some work done on it with new cap and battery leak repair. All traces tested and ic's.(by service-person). It has an 80.0000mhz oscillator.
I've read on EAB posts that the 040 cpu has a divisor function that halves the clock frequency whereas the 060 version does not. Also the resistors in the CLKEN section under the cpu supposedly reflect this with a resistor in CLKEN->CLK for async use of the 040 cpu divider with an 80.0000mhz oscillator for 40mhz cpu or a resistor in CLKEN->GND in the case of an 060 cpu with a 50.0000mhz oscillator for a sync 50mhz cpu.
I've seen pictures of both async and sync on 040 Apollo cards! My card is currently CLKEN->GND with a 80.0000 oscillator which would mean double-clocking the cpu to 80mhz and running the 60ns ram at double speed? Seems wrong!.
Any insight on this or if various revision board/roms were configured differently?? Thanks.

[utri007]

Depending your Amiga 1200 motherboard revision, you will need to make timing fixes for it.

I had (still have but upgraded it to 68060) Apollo 68040 accelerator and Rev1d4 motherboard it worked with 3.0 kickstart, but not with 3.1 kickstart, couldn't make it work with rev 2b motherboard at all untill I made timing fixes both motherboards. Now it works both my Amiga 1200 motherboards.

[Snoopy1234]

Originally Posted by utri007

Depending your Amiga 1200 motherboard revision, you will need to make timing fixes for it.

I had (still have but upgraded it to 68060) Apollo 68040 accelerator and Rev1d4 motherboard it worked with 3.0 kickstart, but not with 3.1 kickstart, couldn't make it work with rev 2b motherboard at all untill I made timing fixes both motherboards. Now it works both my Amiga 1200 motherboards.

Great you've won the battle! I have a 1D4 w/timing fix done, KS 3.1 and another one KS 3.1 which I haven't checked the revision and no fix. I was more wondering about the cpu clock circuit on my card whether it has been altered and causing it to brick.

[Snoopy1234]

[QUOTE=Boing-Ball;1578298]040 CPU are 1/2 the XTAL/Oscillator clock speed. So 80mhz = 40mhz on the CPU. 060 CPU will run same as the oscillator I.e 50mhz = 50mhz CPU speed.

I'm curious if the clken resistor on the board is in the clk or gnd position? It's beneath the capacitor - reverse of the cpu.

[Jope]

The clock halving is done by the 7474 chip next to the RTC battery. The 040/060 jumper selects whether the oscillator's signal goes directly to the CPU socket or via the 7474.

No idea about the caps/resistors under the CPU though.

[utri007]

Originally Posted by Boing-Ball

Something to note is you need a good PSU for these cards to keep them stable. I.e 50watt or higher PSU. Not the standard 25watt PSU.

That is good point, original Amiga 1200 woun't do.

[Snoopy1234]

Originally Posted by Jope

The clock halving is done by the 7474 chip next to the RTC battery. The 040/060 jumper selects whether the oscillator's signal goes directly to the CPU socket or via the 7474.

No idea about the caps/resistors under the CPU though.

I see the 7474 completes the task on an 040. other posts are saying there is an internal divisor pipeline in the Motorola 040 and the 7474 is like the circuit header.

I looked at John Hertel's clock diagram for the 1240 and the traces are colour schemed. The "pink" 040 clk circuit shows clken->clk as the 040 circuit activating the divisor cpu pipeline for 40mhz (80mhz).. So why are many 040 cards soldered clken->gnd which is supposedly the 060 configuration?

Here are my references: One from EAB- 2010 and the opposite view from John Hertels blog on 1240->1260 conversion...

http://eab.abime.net/showpost.php?p=...&postcount=314

http://wordpress.hertell.nu/?p=474