Overclocking a Turbo 040 - Results

[olePigeon]

Just thought I'd post my experience, and the issues I had with the overclocking.  Turns out my initial problem was my DougG3 ROM.  For whatever reason it was making my IIci death chime.

Processor:  MC68040RC40

Speed:  50MHz (25MHz crystal)

Issues:

• Lost System icons (Finder, Enablers, System, etc. became generic documents.)
• Internal and external floppy drives could not read floppies
• Would sometimes freeze when attempting to shut down

Speed:  48MHz (24MHz crystal)
Issues:

• Internal and external floppy drives could not read floppies

Speed:  44MHz (22MHz crystal)
Issues:

• None.

So, the furthest I could overclock it without any issues was 44MHz.  I wonder why the floppy drives would stop working?

Here're some pictures of my setup.  I added a socket for the crystal and a fan.

 

[BadGoldEagle]

nice! 

Your IIci now kicks @ss!

How long does it take to boot? (how short is more appropriate I think for this beast)

Have you recapped your PSU with higher rating caps to achieve this?

Odd that the Dougg3 ROM crashed the IIci. What ROM were you using? Stock IIci ?

I know of a program that let you capture your own ROM, but I think it only works for early compacts... Maybe the programmed ROM you used is too early for the Turbo 040? You should definitely try again with the custom ROM because with an OS-in-ROM setup it will be even faster! It would rip the world of 68k apart! I'm sure it's faster than the original stock PPC 601!

I'm not too familiar with 040s, does it disable the 030 or does it uses both?

 

[olePigeon]

I'd have to time it, the problem is that it also has 128MBs of RAM and takes a good 5 minutes just to get past the RAM check.

I'm using a custom ROM that DougG3 made for me.  It has custom startup chime, Happy Mac, and floppy question mark (you can see it on my user icon), as well as the Daystar Turbo 040 init built in.  Looking on my ROM SIMM, it has a bit of corrosion on the pins.  I cleaned as best I could and it started working again.

The Daystar 040 replaces the 030 completely via the PDS slot.

 

[BadGoldEagle]

5 minutes worth of RAM check is 5 minutes too much! 

Have a look at this about the Turbo 040, under "expert options".

If you fiddle with the utility, you can disable RAM check. Just hold the option key and you get advanced features.

Disable Memory Test does exactly what it says: It speeds starting up your Mac by removing the mostly unnecessary RAM Test. If the RAM in your Mac was working before, chances are it’s still working now. The startup RAM check is only really useful when you’ve just installed new RAM in your Mac. It’s good at detecting grossly defective RAM. But once some RAM has proved itself good, there’s no sense in continuing to check it. Save yourself the time and Disable Memory Test.

About that ROM SIMM, something is wrong here. But you will need a ROM programmer to reprogram your Dougg3.

Does it crash before startup or at startup? After the chime?

 

[olePigeon]

I did not know about the Expert options by holding down the Option key.  I'll need to look at it.

I have a ROM programmer.  The IIci death chimed immediately on power-on, before the Mac bong.

 

[BadGoldEagle]

 The IIci death chimed immediately on power-on, before the Mac bong.

So I think the ROM itself is wrong. Otherwise it would have tried to boot and then crash.

 

[Unknown_K]

I just checked on of my Daystars with the cooling fan and the oscillator is 24mhz so the CPU is running at 48. This daystar is the original version with no cache card attached.

 

[Paralel]

The floppies stop working after a certain speed due to timing issues, no?

 

[olePigeon]

I have no idea.  I was hoping the Turbo 040 didn't fiddle with the BUS or timing somehow, and that the CPU could be clocked independently of any other systems.

 

[Paralel]

Unless you can find another clock crystal somewhere that is rated similar to the default CPU speed on the LB, it must use the CPU oscillator for system timing.

 

[olePigeon]

Darn.  Can't sniff at an extra 4MHz, though.

I wonder if it'd be possible to make an intermediary board that you stick between the Daystar and the PDS slot that separates the timings with two crystals.  You could then overclock the Turbo 040 without messing up the timing of the other components.

 

[Paralel]

Should be possible, you just have to interpose a board between the card and the slot that routes the pin that links the oscillator to the system for timing to one that is present on the interposed board, then the oscillator on the board for the Turbo 040 would be used for CPU timing only.

Not sure what happens when the CPU timing starts to diverge from the system timing. Could be ok, could be huge trouble. Depends on if anything in the system depends on a sync between the system timings and the CPU.

 

[olePigeon]

Wish I was knowledgable about that stuff.  Maybe I'll win the PowerBall this week and I can hire one of you guys to make one and test it.

 

[EtherRad]

This is a great thread. Were you able to get the DougG3 ROM to work with the Turbo 040? I've been trying to learn 68k assembly to little avail, it seems like the Turbo ROM references against the gestalt ID on the motherboard ROM if that has anything to do with it?

I have a new 68040RC40A that just came in and waiting on new oscillators to see this CPU's individual max. I use the Turbo 040 in my SE/30 with a TwinSpark, Asanté card, and SCSI2D. If I can get my CPU to 48MHz, would it help to change anything on the floppy drive itself to restore functionality?

For the DougG3 ROM, I was hoping to change the startup box to remove the IIci looking icon and also change the desktop icon to look something like a RAM drive. I'd like just a blank screen with 'Press R for ROM Boot' text only. Then default to the Turbo-Happy-Mac icon rather than Pirate-Happy-Mac icon.

 

[corradokid]

This is a great thread. Were you able to get the DougG3 ROM to work with the Turbo 040? I've been trying to learn 68k assembly to little avail, it seems like the Turbo ROM references against the gestalt ID on the motherboard ROM if that has anything to do with it?"

I'm also very interested in this! Have a programable ROM (2MB) for my IIci, though with a newly acquired Daystar Turbo 040 I've had to go back to a stock ROM to get it operating (assuming it's the ROM checksum as per http://www.synack.net/~bbraun/macromboot.html .)I do have the ROM programmer so I could reprogram a modded ROM with Turbo 040 tweak (hacked ROM checksum?) if one's available!