NeXT Computers

[helf]

sooo... would you mod my turbo color for a price?
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*INACTIVE*

[Slab]

Your benchmark results compare well with the Pyro and Nitro. Thanks for posting them. Now where did I put my soldering iron?
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Slab

[gborgns]

I just added a couple of added pictures and a corrected schematic to the original post.

The schematic was corrected to show a jumper on U6 to force the motherboard to think it is running at 33MHz, regardless of speed switch setting. I found if I didn't do this, the motherboard thought it was running at 25MHz when set to 50MHz. This caused VRAM errors on boot.

Added schematic for the homemade clock doubler.

The pictures show the completed installation.
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Turbo Color Slab, Tadpole P1000G and SS5

[Slab]

Ok, I’m trying to gather the parts and information to overclock my 33Mhz Turbo Color Slab. I have a few questions.

1. You swapped the MC88915 chip for a 100Mhz part. Would a faster part work, such as a 133Mhz or 160Mhz MC88915 chip?
2. Do you have a current source for the parts?
3. You mention the need for a ground plane PC board for the doubler circuit, do you have a current source for that?
4. Folks on several Amiga forums mention that Motorola made some 68040 40Mhz chips with a K63H & L88M mask that were die shrinks, and they supposedly ran cool to the touch, with no heat sink required. Would it be possible to run one of those at 66Mhz with proper cooling? What modifications/hardware would be required to attempt that? Do you think that other peripherals on the bus would run at that speed?

Thanks in advance for your help.
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Slab

[gborgns]

To answer your questions:

1. Yes, a 133MHz or 160MHz MC88915 would work.

2. Current source for parts:

I bought 2 each of the MC88915 and MC88916 from Digi-key. They no longer seems to stock them. Looks like Arrow Electronics might have them. http://www.arrow.com/

Here is the list of parts for purchase from Arrow:

Arrow Part Number : Cost : Value : Size : Type : Comment
C1206C106K8PACTU : 10 for $1.82 : 10uF @ 10V : 1206 : Ceramic : Cut strip
C1206C104M5RACTU : 10 for $1.76 : 0.1uF @ 50V : 1206 : Ceramic : Cut strip
RMCF 1/8 330 5% R : 10 for $1.75 : 330 ohm : 1206 : Thick film : Cut strip
RMCF 1/10 47 5% R : 10 for $1.75 : 47 ohm : 0805 : Thick film : Cut strip
RMCF 1/8 1M 5% R : 10 for $1.75 : 1M ohm : 1206 : Thick film : Cut strip

3. Doubler circuit card:
I used a custom modified model 9210 Surfboard for the circuit card: http://www.capitaladvanced.com/9210.htm I bought it from a local electronics store, Fry's. They have many distributors or you can order it from Digi-key http://www.digikey.com/ I used a piece of copper tape on the bottom for the ground plane.

4. A 40MHz 68040 would work. However, since it will be running at 50MHz, you will still need a cooling solution (i.e. heat sink and fan).

Good luck with your mod.
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Turbo Color Slab, Tadpole P1000G and SS5

[sdinet]

hey guys, I am about 80% complete with my 50mhz mod using gborgns surfboard clock doubler design, will post photos in the next couple weeks!

[Rob Blessin Black Hole]