After upgrading to MacOS X 10.2., I decided to put a fanless Geforc2MX into to my Cube.

I've already tried with a PixelView 2MX Twinview from my PC. But without flashing a BIOS, it wasn't possible to boot the 10.2 installer CD. However, I could boot successfully to MacOSX 10.15 and MacOS 9. This was possible because the Cube Firmware 4.18 already contains a 2mx BIOS. See details here:
http://www.xlr8yourmac.com/G4ZONE/G4firmwareMXrom.html#storytop.

Because the PixelView 2mx has a fan, and it's in use in my PC, I started to look for a fanless 2mx card. Eventually, I managed to buy a Elsa Gladiac 2MX with 32MB of RAM for about 25EUR. The card has a relatively big heat sink, however the cooling fins do not support the airflow in a cube. On the other hand, there's a hole for a screw exactly at the right position for attaching the card to the cube's chassis (like the original ATI graphics card).

The speed gain with Quartz Extreme was surprising, the whole interface became fluid as water. However, the card overheated after a few minutes of using OpenGL (Quake 1). Well, maybe I should have read this page in advance: http://www.cybercoment.com/macgeforce.htm

The reason for overheating is the higher clock speed of the apple cards: while the Gladiac normally runs at 175Mhz core and 166Mhz memory when used on a PC (175/166), it seems to run at a higher clock speed of (200/183) when setup by the apple firmware bios. (The mac firmware controls the card clock speed, true of all Mac cards. There have been various tweaks for this in the past to reduce or overclock the core/ram speeds.-Mike) For a fanless card this seems to be too much, especially for the Gladiac. The PixelView 2MX Twinview went fine at 200/183, but has a fan (Bah).

In order to get the Gladiac 2mx running stable, its clock speed must be lowered to meet its specs or even less. The lower the clock speed, the cooler the card. Power consumption also decreases, this might be a big deal for cube owners with CPU upgrade and/or a lot of extra gear plugged in.

Since the clock information is stored in the BIOS of the card. it should be possible to change the clock speed by changing the corresponding values in the card's BIOS. The trick is to find these values and change them to more appropriate ones.

While most PC-related article discuss overclocking in order to increase the speed of the card, my goal was to lower the clock speed to allow the card runing fanless and stable in an Apple Cube.

I decided to underclock from 200/183 to 166/166 Mhz. This is below/within the specs of the Gladiac. The memory clock matches the specs, while the core clock is about 5% lower. If you're trying this out, I would consider an even less clock (133/133) because the card still gets reasonably hot in the cube (however the heat sink can stil be touthced with bare fingers). The following instructions use clock speeds of 166/166 setting as examle values.

For editing the BIOS, you'll need the ROM image (I tried 1027 and 1075 Twinview, available here: http://www.eden.net.nz/7/20011005geforce2mx.html)

Next you need a hex-editor for the PC. I used UltraEdit. XVI32 or any other hex editor is just fine, too.
(Note - there's a utility for easy modifying the GeForce2MX rom available at http://macmagna.free.fr/-Mike)

As stated on http://mozcom.com/~ronnieg/articles/gf2mx.html, the clock values are stored as Value = Clock in Mhz * 10, so the value for 200 Mhz would 200* 100 = 20000. In little endian hex notation, this equals 20 4E (32 + 4*4096 + 14 * 256)

With this information, we can modify the values for the following clock speeds:

• 200Mhz = 20000 = 20 4E
• 183Mhz = 18300 = 7C 47
• 166Mhz = 16600 = D8 40

Now the tricky part (examples are valid for the 1027 rom, but the approach also works with the 1075 rom):

Follow these instructions to obtain the 1027 ROM image:
http://www.xlr8yourmac.com/graphics/flash_PC_geforce2mx.html

You can also download ROM images from these places:
http://www.cybercoment.com/macgeforce.htm
http://www.eden.net.nz/7/20011005geforce2mx.html

Open the bios image with your hex-editor and search for occurences of 20 4e. You will find it at a lot of places. I was completely lost, until I assumed the clock values would be stored next to each other in some kind of data structure.

There are two of these data structures:

• The first at 0x6e1d, from where we can find the values 7c 47 20 4e sixteen times (8 times in 1075 rom).
  
  
• The second at 0x7a11, where 20 4e can be found 16 times in a row, followed by 16 occurences of 7c 47 (version 1027 and 1075)

In order to change the clock speed, change all the values to the desired clock speed. I replaced all values with d8 40 (166Mhz), because I've chosen to have core/memory clock the same.
After changing values, verify what you've changed as well as the size of the ROM . Use a PC to flash the card. A PCI graphics-card is mandatory if you want to have a second shot. I flashed the 1027 rom as described here:
www.xlr8yourmac.com/graphics/flash_PC_geforce2mx.html

I got a checksum error at 45056 (right number?), but this turned out to be okay, because the ROM really is only that big (and not 64K, as the file size suggests)

In a first attempt I only changed the values in the first structure only, with no effect.

After having changed all values (in first and second struct), the card worked as expected. I assume that its only necessary to change the second data structure (and ignoring the first). Could someone verify this?

I retried with the 1075 rom image (altough the Gladiac isn't twinview) and it also works fine.

The result is a Cube with a fanless card capable of running Quartz Extreme for the cost of about 25 bucks and an evening of fun.
Kind regards, Jens-Olaf Hemprich (jenz@alpenmil.ch)

Another reader replied to this article:

" Hi Mike
I just thought I'd email you after reading the article on under clocking a GeForce 2 to use in a Cube.

I recently purchased an Asus 7100 Pro 64 Mb GeForce 2 MX 400 for about 100 AUD probably only 50 USD. This card has a reasonably sized heatsink and no fan. I bought this card in hope that it would already have a Mac ROM as apparently some of the ASUS 7100's do, it didn't. However I then went on to flash it using the files and instructions available at http://www.cybercoment.com/macgeforce.htm and the card worked fine. I only just noticed but this site says that 64 Mb GeForce cards will not work but this one does. Mac OS 9 and X both report the card as having 64 Mb which surprised me as I thought the ROM determined how much RAM was used on the card.

I've used it in OS 9 and 10.1.5 When I upgraded to 10.2 some of the resolutions stopped appearing as recommended ones, although they were still available by un-ticking "show recommended only" and worked fine when selected.

I've been using this card for about a month now, it does get hotter than the Rage 128 but it has never overheated or caused any problems even after extensive use or a couple of hours of gaming. The only slight problem is that when the Cubes end bracket is used the card does not seat 100% in the AGP slot although it is secure and works perfectly. A little filing of the end bracket is all thats needed if you want a perfect fit. QE is enabled and the card is a huge improvement over the old card, I would not be surprised if this is the best card that can be used in a Cube without a fan.

The other day I also noticed a Mac GeForce 2 ROM editor is available at http://macmagna.free.fr/ for over and under clocking the card
Hope this is helpful and thanks for the great site.
Adam "

I had posted the ROM editor link in the main site news earlier this year when it was released the french site macbidouille.com but had forgotten about it. The macmagna.free.fr site has the utility linked as well as others like the ATI 8500 ROM editor. (See forums video card section here for past comments on flashing PC 8500 cards, etc.)

Related Articles:
For previous reviews and graphics cards related articles, see the Video topics page link below. The Systems page, Cube section has other Cube related articles. For those that missed past news/articles here - the fastest card currently that fits the Cube without mods is the OEM Mac GeForce3. (But it has a fan and you really should install a 80mm fan in the Cube case in addition for cooling.) I and several readers have been running OEM Mac GF3 cards in Cubes with Dual G4/500s and other CPU upgrades modes for some time - but there's never any guarantee of long or short-term reliability with mods like this. The Geforce4MX and faster Nvidia cards won't fit the Cube and as noted in the FAQ, the GF4MX and GF4 Ti Mac roms have to date never been reported to work when flashed in PC versions of those cards. (Ditto for the GF3 Ti series - the Mac rom/card was a pre-Ti version.)