Apollo 1230 cpu replacement

[Beowulf]

Howdy

I have an Apollo 1230 accellerator. Im having problems with it, i.e. ram. Im pretty sure the cpu on it is only 16mhz  :-o
The clock rating on the chip has been rubbed off but im sure I can see 16 on the cpu description. I dont why this is so because these boards came out with the lowest cpu rating being 33mhz.
The crystal is 40mhz so if the cpu is at 16mhz im assuming this would cause instability with the card because that is quite an overclock!  
Any way the current cpu is of the QFP package type and the card has an empty PGA socket. So I want to remove the existing QFP 16mhz cpu and install a 40mhz 68030 PGA type in the PGA socket.
Would this work? Or would the PGA socket be disabled some how because the board had a QFP cpu installed?
Anyone know what im talking about?
 :-?  :-o

[shoggoth]

I'm not sure, but the PGA socket may be intended for a 68881/68882 FPU, not a CPU.

-- Peter

[Beowulf]

@shoggoth

No, the FPU has a PLLC socket. The PGA socket is next to it.

[Tahoe]

If you have the Apollo 1230 MK3 (this one) you should be able to swap the SMD one with a PGA as pictured. Can't tell you if you need to alter any jumper/solderpads but wouldn't think so.

[Beowulf]

@Tahoe


Yes I do have the MkIII. If I get a 40mhz 68030 and use a 33mhz FPU with a 40mhz crystal would this sycrhonize the CPU and FPU? i.e. keep the CPU at 40mhz and bring the FPU up to 40mhz from 33mhz or would this cause problems?

[mdivancic]

Beowulf wrote:
Yes I do have the MkIII. If I get a 40mhz 68030 and use a 33mhz FPU with a 40mhz crystal would this sycrhonize the CPU and FPU? i.e. keep the CPU at 40mhz and bring the FPU up to 40mhz from 33mhz or would this cause problems?

I believe that Motorola CPU's use clock frequencies that are double the CPU speed for stability. You 40 mhz crystal provides a 20 mhz processor speed.

Mike

[Tahoe]

Beowulf wrote:

Yes I do have the MkIII. If I get a 40mhz 68030 and use a 33mhz FPU with a 40mhz crystal would this sycrhonize the CPU and FPU? i.e. keep the CPU at 40mhz and bring the FPU up to 40mhz from 33mhz or would this cause problems?

Originally your board came with a 33Mhz EC030 and a 882 33Mhz both running at 40Mhz (they both use the same crystal).

What you could do is either "just" plug in a 40Mhz CPU, that would give you a 030@40Mhz and a 882@40Mhz of which only the 882 is overclocked.

What you could also do is replace both the 030 and 882 with 50Mhz versions and replace the crystal.

Try to get a hold of a full 030 instead of an EC version while you have the chance, that gives you an MMU.

[Tahoe]

BTW: Just read you think your problems are RAM related, did you set/unset the RAM jumper (60ns)? Problem can be caused by having it set at 60ns while the SIMM can only handle 70.

[Beowulf]

Yes

I tried adjusting the jumpers it might be the ram i have. Im not sure if any of the ram sticks are functioning because I have now way of testing them.

If I get a 40mhz 030 and a 33mhz fpu do I need to change the 40mhz crystal I already have to clock them both at 40mhz?

If i get a 50mhz cpu and fpu do i need a 100mhz crystal?

[Brian]

No... only the 68040 CPU halfen the clock speed given to it, so a 50Mhz crystal is what you need to clock your 68030 to 50mhz.

As you have troubles with the card and knowing there's overclocked components on it I'd first remove the FPU to rule out that. Also I'm sure you can get hold of a different simm just to test. If you decide to go for 50Mhz you'll need to replace the FPU for at least a 40Mhz version also or it'll burn soon (I also suggest some kind of cooling on both the CPU and FPU, if atleast an as big as possible peice of aluminium sheet will probably still fit underneath without any big mods to the computer).