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DayStar Digital Turbo 040 Overclock

Some notes by Tyler Sable, spam at fenestrated dot net.

Theory | Pictures | Links

The DayStar Digital Turbo 040 card is an accelerator for Macintosh computers based on the Motorola MC68030 microprocessor. It fits into the cache slot of a Mac IIci computer, and with adaptors can be used in many other Macs. Notably, the SE/30 can be dramatically accelerated with this card. I've written about it before, on Low End Mac.

Theory

The Turbo040 implements a data/address bus for the 68040 chip on-card, and the Turbo040 ASIC (or chipset, for earlier versions) takes care of passing data between the host Mac and this on-card bus. The bus (and thus the 68040 chip) runs at twice the speed of a standard 4-pin crystal oscillator soldered onto the card.

By desoldering the crystal oscillator and installing an appropriate socket, new crystals (and thus new CPU speeds) can be easily slotted into place and tried. DayStar wasn't kidding around when they attached these, and desoldering may not be as easy as it should. Also, remember that Turbo040s aren't getting any easier to find; be careful not to ruin your accelerator!

These crystals seem to be going out of production: there are fewer listed here than were available when I modified my card in 2005. You may have to scavenge from other old equipment.

DigiKey part numbers:
SocketA462-ND
Crystal SpeedPart #68040 Speed
12MHzCTX131-ND24MHz
14.3MHzCTX205-ND28.6MHz
18.4MHzCTX207-ND36.8MHz
19.6MHzCTX208-ND39.2MHz
20MHzCTX209-ND40MHz
24MHzCTX210-ND48MHz
25MHzCTX211-ND50MHz

Pictures: 48MHz Turbo040 | Top

As you can see, I went a little crazy with my Turbo040 card. It started out as a 40MHz Turbo040. I added a socket for the crystal oscillator, down in the lower-left corner. Testing revealed that it would run no faster than 40MHz.

I added a lot of little heatsinks to the cache SRAM chips and the ASIC. The thin DayStar heatsink has been reattached using the old video card overclocker's trick of arctic silver and super glue, and a laptop-style sideways blowing fan added to increase airflow through the card stack.

This 40MHz Turbo 040 actually came overclocked! DayStar shipped it with a 33MHz 68040 chip clocked at 40MHz. That a lowly 33MHz chip ran at 48MHz for any length of time was amazing! I swapped the 33MHz chip out for a real 40MHz one, and now 48MHz is extremely stable. 50MHz is usable, but crashes about once per day. The speed difference between 48 and 50MHz is unnoticable, so I choose stability

When using the Turbo040 with a Macintosh IIsi Daystar Adaptor, the Turbo040 is sandwiched right up against another expansion card. (An Asante ethernet card, in my SE/30.) Consequently, there is very little room to add a powerful CPU heatsink. I'm confident that in a IIci or other roomy Mac, a larger heatsink would make 50MHz (or more) readily attainable.

Previously, a GPU cooler from a GeForce 4 AGP card took care of the 68040. The fan in this heatsink eventually failed and I upgraded to the current setup you see above.

Links | Top

20MHz Turbo 040i overclock by Brad Wilson
33MHz Turbo040 overclock by Tan Tywee
40MHz Turbo040 overclock by Marc Schrier

I have used my Turbo 040 at 48 and 50MHz for quite some time now, and I have never noticed the floppy drive problems described on the pages above. 800k and 1.44MB floppy disks work fine in my SE/30 with Turbo 040 @ 48MHz.

Turbo040 revision ID guide @ artmix.com, maker of the fabulous, expensive TwinSpark Adaptor for SE/30 owners. In Japanese

Turbo040 ROM version FAQ also @ artmix.com. In Japanese

DayStar Sales page about Turbo 040 archived @ lowendmac.com

Powered By DayStar sticker. I carefully traced a picture of the original Powered by DayStar sticker that shipped with DayStar accelerators. Now, an accurate reproduction is available! Just download, print, clip, and tape this file and show off your DayStar pride!

Text and Images copyright 2003-2008 Tyler Sable