I have a P166MMX running on a Rev 1.51 board and a K6 233 on a Rev 1.55 board.

So, popped the 233MMX in and did some experimenting. Tested all 16 possible FSB speed/multiplier combos, and while the MMX chip boots just fine, it seems to interpret the 1.5 multiplier jumper setting as 2.0 (expected 3.5), and the 3.0 one as 2.5. Here's a table:

1FSB	Multi   Freq   Note
250    1,5     100	 50*2?
355    1,5     110	 55*2?
460    1,5     120	 60*2?
566    1,5     133	 66*2?
650    2,0     100	
755    2,0     110	
860    2,0     120	
966    2,0     133	
1050    2,5     125	
1155    2,5     133	
1260    2,5     150	
1366    2,5     166	
1450    3,0     125	 50*2,5?
1555    3,0     133	 55*2,5?
1660    3,0     150	 60*2,5?
1766    3,0     166	 66*2,5?

Kind of odd behaviour, can it be explained, and perhaps even fixed somehow?

Also did some testing with Setmul and Speedsys. What's interesting here is that all the TR12 options (BPD, VPD, L1DX, CCD, DCD) seems to work, thought they weren't supposed to with MMX chips. Another table, using 66*2.5=166MHz as baseline:

1No switches:      124.57
2BPD:              106.46
3VPD:              118.64
4L1DX:             33.40
5CCD:              68.09
6DCD:              46.40
7All of the above: 26.17

Not that I complain, but thought it was common consensus that the test registers were disabled on MMX chips other than PODs.

I think at one time it was thought that regular MMX did not do TR12, mainly because my POD worked while one other person's 233MMX did not. But since then some other people on here have come forward with their MMX cpu working. lvader has results of his 233MMX on the cachebench chart. I put his results on their own tab because he wired his FSB to some case switches and was able to get a much wider range of results. It's nice to see them all without being mixed in with the other results.

kaputnik wrote:

So, popped the 233MMX in and did some experimenting. Tested all 16 possible FSB speed/multiplier combos, and while the MMX chip […]
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So, popped the 233MMX in and did some experimenting. Tested all 16 possible FSB speed/multiplier combos, and while the MMX chip boots just fine, it seems to interpret the 1.5 multiplier jumper setting as 2.0 (expected 3.5), and the 3.0 one as 2.5. Here's a table:

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1FSB	Multi   Freq   Note
250    1,5     100	 50*2?
355    1,5     110	 55*2?
460    1,5     120	 60*2?
566    1,5     133	 66*2?
650    2,0     100	
755    2,0     110	
860    2,0     120	
966    2,0     133	
1050    2,5     125	
1155    2,5     133	
1260    2,5     150	
1366    2,5     166	
1450    3,0     125	 50*2,5?
1555    3,0     133	 55*2,5?
1660    3,0     150	 60*2,5?
1766    3,0     166	 66*2,5?

Kind of odd behaviour, can it be explained, and perhaps even fixed somehow?

Also did some testing with Setmul and Speedsys. What's interesting here is that all the TR12 options (BPD, VPD, L1DX, CCD, DCD) seems to work, thought they weren't supposed to with MMX chips. Another table, using 66*2.5=166MHz as baseline:

Copy code to clipboard

1No switches:      124.57
2BPD:              106.46
3VPD:              118.64
4L1DX:             33.40
5CCD:              68.09
6DCD:              46.40
7All of the above: 26.17

Not that I complain, but thought it was common consensus that the test registers were disabled on MMX chips other than PODs.

I have an explanation and possible fix.
The multiplier settings on both P54C and P55C are determined by BF0 and BF1 pins, but P54C and P55C respond differently when the two pins are float.
P54C: both are pulled high.
P55C: BF0 is pulled low, BF1 is pulled high.

So if your board can only toggle the two pins between pulled low and float, lacking the ability of pulling them up, you will observe the described multiplier outcome. You can confirm this by measuring the voltage on the pins.

To fix it you can jump wire the floating pin of the jumper/switch to VCC3 with a 1k ohm resistor.

Here is an article describing a similar problem and the solution.
http://vobarian.com/8500tvx.html

clueless1 wrote:

I think at one time it was thought that regular MMX did not do TR12, mainly because my POD worked while one other person's 233MMX did not. But since then some other people on here have come forward with their MMX cpu working. lvader has results of his 233MMX on the cachebench chart. I put his results on their own tab because he wired his FSB to some case switches and was able to get a much wider range of results. It's nice to see them all without being mixed in with the other results.

Ah, that explains it. Quite sure I at least partly got that info from the discussion in your benchmarking thread 😀

lazibayer wrote:

I have an explanation and possible fix. The multiplier settings on both P54C and P55C are determined by BF0 and BF1 pins, but P5 […]
Show full quote

I have an explanation and possible fix.
The multiplier settings on both P54C and P55C are determined by BF0 and BF1 pins, but P54C and P55C respond differently when the two pins are float.
P54C: both are pulled high.
P55C: BF0 is pulled low, BF1 is pulled high.

So if your board can only toggle the two pins between pulled low and float, lacking the ability of pulling them up, you will observe the described multiplier outcome. You can confirm this by measuring the voltage on the pins.

To fix it you can jump wire the floating pin of the jumper/switch to VCC3 with a 1k ohm resistor.

Ah, that must be it, thanks! Got my jumper headers wired up to a bunch of SPDT switches used as SPST ones mounted on a 3.5" bay panel. Posted a few pics of the mod, if you're interested. At a glance it looks like it should be easy enough to implement if I got it right, will just have to replace the BF0 switch with a SPDT on-off-on one, and find some point on the board to connect it to VCC3 through that resistor, or just rewire the existing switch between VCC3 and ground 😀

lazibayer wrote:

I have an explanation and possible fix. The multiplier settings on both P54C and P55C are determined by BF0 and BF1 pins, but P5 […]
Show full quote

I have an explanation and possible fix.
The multiplier settings on both P54C and P55C are determined by BF0 and BF1 pins, but P54C and P55C respond differently when the two pins are float.
P54C: both are pulled high.
P55C: BF0 is pulled low, BF1 is pulled high.

So if your board can only toggle the two pins between pulled low and float, lacking the ability of pulling them up, you will observe the described multiplier outcome. You can confirm this by measuring the voltage on the pins.

To fix it you can jump wire the floating pin of the jumper/switch to VCC3 with a 1k ohm resistor.

So, did the hack tonight, works like a charm 😀 Was some work with it though.

First I removed the CPU from the socket, located the VCC3 holes, put a sewing pin in one of them, and closed the socket to make contact. Started continuity testing all jumper headers I could find on the board. Nothing...

Began searching for some other point to tap in on the VCC3 plane. Quickly found that two pins of the unpopulated and undocumented header JP4 was connected to it, so decided to pull the mobo from the case, and populate the header. Did that, and put the computer back together again. Rewired my custom BF0 front panel switch, and patched in a 1kohm resistor. Used the same method with the sewing pin to find out which one of the BF0 jumper pins that is the floating one.

Only thing left to do now is writing a new frequency table for the front panel 😀

kaputnik wrote:

So, did the hack tonight, works like a charm :) Was some work with it though. […]
Show full quote

So, did the hack tonight, works like a charm 😀 Was some work with it though.

First I removed the CPU from the socket, located the VCC3 holes, put a sewing pin in one of them, and closed the socket to make contact. Started continuity testing all jumper headers I could find on the board. Nothing...

Began searching for some other point to tap in on the VCC3 plane. Quickly found that two pins of the unpopulated and undocumented header JP4 was connected to it, so decided to pull the mobo from the case, and populate the header. Did that, and put the computer back together again. Rewired my custom BF0 front panel switch, and patched in a 1kohm resistor. Used the same method with the sewing pin to find out which one of the BF0 jumper pins that is the floating one.

Only thing left to do now is writing a new frequency table for the front panel 😀

Haha nice!

Necro time!

I have Rev 1.52 of the GA-586HX. BIOS is the latest.
The manual states, that I can use MMX166 and MMX200:

Is this true? Do the normal jumper settings work for the MMX200?
Can I use it without modifications?

elianda wrote on 2017-07-16, 13:14:

I have a P166MMX running on a Rev 1.51 board and a K6 233 on a Rev 1.55 board.

I have also a Rev 1.55 here with Pentium 133.
How do i have to set the board for the AMD K6 233 ANR and do I have to modify something?

Oh yeah, this is relevant to a thread I started the other day.

Re: Bf0, Bf1, Bf2 Multiplier Mod

Follow it, I’m hoping to eventually have a pcb that can be soldered to the back of the motherboard with a bunch of tricks built in to solve problems like this.

I am not familiar with this board or its versions. But images that I see look like it’s from the time right after socket 5 so it’s possible that some of these boards may be single plane and socket 7 (a oxymoron, I know) but anyway, if the manual for your version claims that it supports a non overdrive mmx cpu, then it should be dual plane.

If it’s dual plane then you can probably use whatever socket 5/7/ss7 cpu you want all the way up to a 400-500mhz k6-3+

But you’ll probably want to look into a patched bios for that.
DIY Bios Modding guide Jan Steunebrink k6-2+/3+ 128gb

But yeah, if it supports a 166 mmx then it will support a 233mmx.

If your multipliers are acting funny, then it’s probably because of the reasons mentioned in above replies. (Also see my 1st link)