ABIT BM6 – Will the Iceman Cometh?

Suppose ABIT makes baseballs. They make some of the best baseballs around – the most popular one is the BH6 baseball. With a 32 ounce bat, it’s a home run every time. Now they introduce the BM6 baseball – only problem is you can only use a 16 ounce bat; lucky to hit a single. Which would you buy?

Well, in a nutshell, the problem I have with the BM6 is not the BM6 – it’s cooling (the bat), as in the lack of adequate. Socket 370 coolers (so far) are puny single fan units – for serious overclocking, they will not cut it. If you push your PPGA to something like 2.3 volts, the average Socket 370 cooler will be overwhelmed. In addition, even if you only push a little bit (like 300a to 450 @ 2.0 volts), the average socket 370 cooler will run the chip hotter than a good PII or Celeron 2 fan cooler.

PC Nut kindly supplied a BM6 and C300a PPGA to test, along with a PC Power and Cooling Z1 socket 370 cooler. Now off the bat I’m not going to run a slew of benchmarks that will tell you it’s as good a board as any other, because it is. There are a bunch of BM6 reviews around and read those for benchmarks.

The BM6 is basically the BH6 with a socket 370 to mount the PPGA. It’s not exactly the same, in fact is some respects it’s better.

Major differences compared to the BH6

First, the BM6 has much better temperature monitoring. It has one thermistor under the CPU, one for the system and a third 2 pin male plug on which you can mount your own thermistor. This is not difficult – go to Radio Shack and get part # 271-110A for about $3 and you now have a temperature probe you can place anywhere; I had a 2 pin female connector from something or other and soldered the thermistor to it and it worked fine. If you feel sick, you can use it as a thermometer or monitor your temperature while playing Quake II – where you place it is up to you. I personally would use it to monitor video chip temperature, but that’s me.

Now, the CPU thermistor is a joke – what it really monitors is the air temperature under the CPU – big deal. If you want to measure CPU temp, there is a workaround: If you look at the middle of the socket 370 hole, you will see a little white eye looking back at you – this is the thermistor. Cut a small piece of tubing so it will fit over the thermistor head. Now cut this little piece of tubing so that it touches the back of the CPU. You don’t have to mount the CPU to do this – use a card as the CPU and measure against it.

Next, once the length is OK, crumple a small bit of aluminum foil and place it in the top half of the little tube. Put a dab of thermal grease on the eye, a dab on the aluminum foil which contacts the CPU, and presto – a thermistor which really monitors CPU temperature (or at least the back of it).

Second, there is a better selection of bus speeds – 66, 75, 83, 100, 105, 110, 112, 115, 120, 124 and 133. These are very nice to have and, as you will see, allowed me to run this particular CPU at a higher speed than possible on the BH6.

Third, there are more PCI settings which help in keeping the peripherals close to spec; you can choose 124 and 133 with the PCI bus divided by 3 or 4, compared to only 133/4 for the BH6. But there is a real screwball setting – at 75 the PCI runs at 75/3 or 25 MHz, while at 83 it is 83/2 or 41.5. Now, I’m sure there is a rational explanation for this that has to do with clock speeds and dividers, but it is damned peculiar. And if you are running at 75 (e.g., C400a @ 6×75 for 450) the peripherals will crawl along at 25 MHz, possibly degrading overall system performance.

Fourth, you can manually assign IRQs for PCI slots 1-4; very handy for resolving conflicts Windows seems sometimes unable to resolve.

Fifth, the clock generator is different; the BH6 uses IC Works W124 and the BM6 uses the W144. This is important if you are using Soft FSB to change bus speeds, so make sure you select W144x if you use Oda’s Soft FSB – works great on both boards.

Sixth, it looks like some of the components on the BM6 are larger; now whether or not size matters is an ongoing debate I will not attempt to answer, but I thought it’s worth a mention.

And last, there is a system monitoring utility called HW Doctor on the CD. Not as robust as other monitor programs but OK nevertheless.

Testing the BM6

No benchmarks – plenty of those around in other reviews (see links below).

What I concentrated on was the BM6’s overclocking stability. To do this I used Soft FSB to vary bus speeds and Prime 95 to test stability. I used a Celeron 300a PPGA supplied by PC Nut, a week 51 Malaysian chip.

I mentioned cooling at the beginning – it should not come as a surprise that better cooling gave me better results, and that’s where I have a problem with socket 370 boards in general. Look at the socket – until someone develops a new cooler, the socket 7 coolers that are out there are inadequate for serious overclocking. Mind you, the cooler is the issue, not the board. BUT developing a great baseball to use with inadequate bats is not going to sell baseballs, and unless inadequate bats are your thing, a socket 370 board is going to disappoint you. I would hold off on a socket 370 board until there are really good cooling solutions available or, as I did, adapt what’s there.

Overclocking and Cooling PPGA’s

So, what did I find on overclocking? Well, this is a real nice board to get your CPU up to speed. Most gratifying are the 105 and 110 bus speeds, which allowed me to get this CPU cranking at a stable 473 (4.5×105) @ 2.0 volts. Nothing I did would get it to run stable (defined as surviving Prime 95) at 110 and 2.3 volts. However, better cooling did allow me to run this CPU at 110 in Windows 98 without crashing while running Prime 95 (although failing the test), and it would probably survive not too intensive use at 110 and 2.3 volts.

As a comparison, I mounted the PPGA on a slot adapter, rubber banding the TennMax TF onto the adapter to hold it in place. Not elegant but works fine. I tried to run the PPGA on the BH6 at 112: It booted but failed at the Windows splash screen. This was at 2.3 volts, similar to the BM6 attempt at 110 and 2.3 volts, so NG at above 105.

There are two things I would recommend for adequate cooling: One, use CPU Idle or Waterfall. Two, adapt a 2 fan Celeron cooler like the TennMax TF and use it on the BM6. On the BM6, this is not an easy task – it will take some ingenuity. I was able to use the TennMax TF because I tested the board outside the case – just plopped it on the ABIT cardboard box, hooked up drives, video and a power supply, and proceeded to test it out on my computer test stand (well, actually my dining room table- my wife is thrilled). Because the BM6 was flat, I could place the TennMax on top of the CPU and rest the overhanging end on the white pins holding the BX chip heatsink. By coincidence, this gives a completely flat platform for a long cooler.

The difference between the Z1 single fan cooler and the 2 fan TennMax TF was enough so that at 4.5×110 2.3 volts, the single fan unit would crash as soon as I selected 110 with Soft FSB. With the TF, 4.5×110 was not stable under Prime 95 but Windows 98 would run OK. The CPU temperature difference averaged 4-5 degrees Centigrade, obviously enough to allow 110. At 4.5×105 running Prime 95, CPU temperature with the Z1 was 43 C and 40.5 with the TF.

At 450 2.0 volts with Waterfall, the TF kept CPU temperature at 26 C and the Z1 30.5. Without Waterfall, the Z1 was 39 C and the TF 35.5. Running the CPU at 450 boosted CPU temp 2.5 C over the stock setting of 300. Any doubters about using software cooling take note.


So after all of this, what do I conclude? The BM6 is a really fine board with features that make it more attractive than the BH6 for overclocking PPGA’s with one major proviso: If serious overclocking is your goal, expect disappointment until you get really good socket 370 coolers or you are prepared to undertake some serious modifications to existing Celeron and PII coolers.

If this is not you cup of tea, then go with the ABIT BX6-2 and a good slot adapter, being prepared to adapt a good Celeron or PII cooler onto the slot adapter. This is what I am doing right now – I have the C300a PPGA running at 450 2.0 volts on my BH6 with the TennMax TF cooler rubber banded to the slot adapter – works great, chip seems happy, completely stable.

Final Comments

It is a shame that a board as good as the BM6 is handicapped by inadequate cooling solutions, but I find it preferable to the BH6 due to the enhanced features of the BM6 for PPGA’s. What would make this an absolutely great board for PPGA’s would be more bus speeds below 100 and enabling PCI dividers of 3 and 4 below 100. Compared to a BX6-2 with a slot adapter and modified cooling, I’d go with the BX6-2 – more upgrading options (re slot 1 chips).

Thanks again to PC Nut for allowing me to play with this stuff – only vendor I recommend without reservation.

Links to Other BM6 Reviews:

AnandTech – Comprehensive as usual.
BX Boards – Another thorough review.
Firing Squad – One of the first BM6 reviews.
OCP – Always a different twist at OCP.
Socket370.com – Go here for BM6 picture and feature list.
Sys Opt – Usual first class review.

Link to Abit’s Site:

ABIT – Who else?

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