Underclocking 1.4GHZ to 733 Concerns

[Bowlsnapper]

Since the ICs for the reduction circuit are getting harder and harder to find, I was thinking that any build I do will involve dual bios options for 1.4GHZ and 733MHZ. That would require that the underclocked bios be set to 66/67MHZ FSB. My question is, would slowing things down that much affect things like memory speeds or anything else affected by it to a degree that would be noticeable? Will I create a bottleneck anywhere else in the system by clocking the FSB that insanely low?

[dust08]

I have been worried about the same and wanted to know before buying a 1.4ghz box. I believe zzattack is going to test some games soon with an underclocked tualatin 1.4ghz hopefully can give us some answers. 

[Bowlsnapper]

2 hours ago, dust08 said:

I have been worried about the same and wanted to know before buying a 1.4ghz box. I believe zzattack is going to test some games soon with an underclocked tualatin 1.4ghz hopefully can give us some answers. 

His "CPU Upgrade x10" thread has been dormant for a while now, and he DID mention that he tends to shift his interests/obsessions often, so I hope he continues his work, as his contributions thus far have been pretty interesting and impressive, and it's rare to see enthusiasm for this niche segment of the hobby.

Glad I'm not the only one wondering about this.

[coldasijs]

There was somebody in another topic who said that you cannot down clock the 1.4 ghz to 733 mhz. Apparently they don’t accept a fsb lower then 100.

 

I still need to test my 1.4 ghz. 

Edited October 9, 2022 by coldasijs

[Bowlsnapper]

1 hour ago, coldasijs said:

There was somebody in another topic who said that you cannot down clock the 1.4 ghz to 733 mhz. Apparently they don’t accept a fsb lower then 100.

 

I still need to test my 1.4 ghz. 

Shit. Well, there goes that idea.

I actually remember this thread. It's a VERY unfortunate problem with the upgrade, but thankfully, the list of games that DO run when patched is not necessarily too small... Can anybody else confirm that the reduction just straight up doesn't work in some/any games at all? If that's the case, then I don't know what its purpose is.

I wish I understood coding so I could understand why some engines are built around CPU timing and others are not.

[Bowlsnapper]

Minimum FSB speeds seem to differ between 1GHZ and 1.4GHZ CPUs. Not even remotely sure why that would be. 

[dust08]

I have seen that thread as well, however I have been messaging zzattack directly about purchasing one of his 1.4ghz boxes and he indeed has an underclocked bios that works at approx 740mhz. I asked if he would be willing to test some games on the underclocked bios referencing that thread for the problem games. Last I heard he literally downloaded the entire xbox library.

My main concerns with compatibility would be the memory speeds with the FSB clocked so low as well as the slight difference from the stock speeds 733 vs. 740. As far as reports that they were unable to underclock 1.4ghz cpus, it's likely that they had a 100mhz FSB celeron tualatin(256k cache) with a 108mhz FSB making it run at 1480mhz, so to get close to stock speeds the FSB would have to go down to around 50mhz which must be too low to boot. 

Edited October 9, 2022 by dust08

[Bowlsnapper]

6 hours ago, dust08 said:

I have seen that thread as well, however I have been messaging zzattack directly about purchasing one of his 1.4ghz boxes and he indeed has an underclocked bios that works at approx 740mhz. I asked if he would be willing to test some games on the underclocked bios referencing that thread for the problem games. Last I heard he literally downloaded the entire xbox library.

My main concerns with compatibility would be the memory speeds with the FSB clocked so low as well as the slight difference from the stock speeds 733 vs. 740. As far as reports that they were unable to underclock 1.4ghz cpus, it's likely that they had a 100mhz FSB celeron tualatin(256k cache) with a 108mhz FSB making it run at 1480mhz, so to get close to stock speeds the FSB would have to go down to around 50mhz which must be too low to boot. 

Hmmm. I'm gonna have to contact him directly about that. If it IS possible, then that would simplify things a LOT, as long as memory speeds don't suffer, of course.

A 7Mhz speedup is, thankfully, not going to be noticeable in most games, so that's not a biggie. And if it is true that they already had to underclock their bios for compatability, then that would have been useful information to have... What would that 100mhz tualatin's stock frequency be if that was the case? What model do you suspect that might be? That would be a much more affordable way to source CPUs, since the ones we want are 100 bucks more than every other P3 on Ebay (SL5SX and SL6BY, the 1.4/133/512 models).

[dust08]

https://www.ebay.com/itm/225181721775?epid=74053811&hash=item346de064af:g:eZYAAOSw5stiER6h&amdata=enc%3AAQAHAAAA0GnhAAADDKZn5cBnGkyaTMPilOuOeeSUkwJMshB419%2Bqkvyy0blquDHqiix9ehrTFD%2FWsF7DaldJoxDJuwUUhK2HKrRqYspvuplwwhCvaCmt3tcx%2FYm9K9rjxcQ%2FJFf%2BxJRaVZKbTcKA4piZklIGQ7Dxg4uWnW31DtbOKiXs2BlrTy1DDG%2BoXmPkKdpThYN3psRvynqrpIbx7kREmRqSUf5G%2Fh2Q7sbpr14NrmYXdT9omuZyuG7%2FlNa%2BCi00n%2BiNBX8ZmfpGkYv%2FujmOjMWp5mw%3D|tkp%3ABk9SR_bsxt_3YA

 

There's one of the 100mhz FSB Tualatins. Using one of those would mean that you could get pretty crazy overclocks if voltages could be changed on the xbox, back in the day people were able to get up to 2ghz with them on watercooling. I believe the old dreamx xboxs used the 100mhz celerons from what I've been able to find.

[Bowlsnapper]

2 hours ago, dust08 said:

https://www.ebay.com/itm/225181721775?epid=74053811&hash=item346de064af:g:eZYAAOSw5stiER6h&amdata=enc%3AAQAHAAAA0GnhAAADDKZn5cBnGkyaTMPilOuOeeSUkwJMshB419%2Bqkvyy0blquDHqiix9ehrTFD%2FWsF7DaldJoxDJuwUUhK2HKrRqYspvuplwwhCvaCmt3tcx%2FYm9K9rjxcQ%2FJFf%2BxJRaVZKbTcKA4piZklIGQ7Dxg4uWnW31DtbOKiXs2BlrTy1DDG%2BoXmPkKdpThYN3psRvynqrpIbx7kREmRqSUf5G%2Fh2Q7sbpr14NrmYXdT9omuZyuG7%2FlNa%2BCi00n%2BiNBX8ZmfpGkYv%2FujmOjMWp5mw%3D|tkp%3ABk9SR_bsxt_3YA

 

There's one of the 100mhz FSB Tualatins. Using one of those would mean that you could get pretty crazy overclocks if voltages could be changed on the xbox, back in the day people were able to get up to 2ghz with them on watercooling. I believe the old dreamx xboxs used the 100mhz celerons from what I've been able to find.

Are you SHITTING me? 2Ghz speeds have been achieved before? ...Dude, are you SURE? How does one even change voltages? Changing SMD components?

And why are the 133Mhz FSB 1.4Ghz processors so much more god damn expensive than ones like this? Do people know we're trying to mod our Xboxes or something?

Edit: ZZ has informed me that it IS possible to underclock the processor to 745Mhz by setting the FSB to 67Mhz. XBOverclock can only make adjustments in 6Mhz increments, and I guess 67Mhz in one of the steps in that table.

I have also been given a starting point for adjusting voltages, although I will have to figure out how to make the necessary adjustments to kick up the SL64V to a point where it would run at 2Ghz... my assumtion being that it would be equal to the big 2 processors - about 1.65 - 1.7. But what do I know?

[dust08]

Not 2ghz on the xbox but on pc socket 370 motherboards that had unlocked voltages.

[Bowlsnapper]

8 minutes ago, dust08 said:

Not 2ghz on the xbox but on pc socket 370 motherboards that had unlocked voltages.

Should be theoretically possible though, shouldn't it? We can adjust the voltages on our mainboards also, albiet in a very painstaking way, but regardless... is there any upper limit to how much we can increase the voltages on the Xbox mobo?

 

Although, upping voltages to the point of enabling functionality DOES traditionally involve trial and error in getting it to a point where the processor runs, but doesn't create unncessary heat. Doin that using hardware mods would be a LOT of work... unless you just throw caution to the wind and start with a voltage that you KNOW will work and just make sure to keep the CPU PLENTY cooled. Does the interposer interfere with changing voltages the traditional way (modifying the IC below the processor)?

[dust08]

I know nothing about changing voltages on an xbox, sure it's possible but you would probably need a better PSU and idk if the ram could handle the FSB speeds needed, would need watercooling, a lot of work basically....

Here's the thread I saw with some great info about overclocking these old tualatins: https://www.vogons.org/viewtopic.php?t=49028

Edit:

another link I found with a lot of really good info when I was researching about these old cpus: http://brassicgamer.blogspot.com/2020/10/the-almost-definitive-piii-tualatin.html

Edited October 9, 2022 by dust08

[Bowlsnapper]

 

Thank you, sir! 

[Prehistoricman]

If RAM speed ever becomes an issue, you can reduce it by 33% by increasing the frequency divider from 2 to 3. On a normal Xbox, that reduces the clock from 200MHz to 133MHz.

The memory frequency divider is the '2' digit in the PLL register that usually has the value 0x00230801.

[Bowlsnapper]

2 minutes ago, Prehistoricman said:

If RAM speed ever becomes an issue, you can reduce it by 33% by increasing the frequency divider from 2 to 3. On a normal Xbox, that reduces the clock from 200MHz to 133MHz.

The memory frequency divider is the '2' digit in the PLL register that usually has the value 0x00230801.

Please forgive my stupidity, but could you clarify that a bit? I'm not as knowledgeable as I would like to be. If RAM speed becomes an issue when slowing down? I actually wasn't aware that you could control memory and CPU speeds independently from one another. Is this an option in XBOverclock? By divider, do you mean multiplier? JESUS I'm retarded.

[Bowlsnapper]

With regard to OCing to 2Ghz, there a LOT of considerations, the PSU is one for sure, but I think an ATX power supply can be used, for experimental puposes temporarily, at least. The other two considerations that come to mind, at the moment anyway, are binning the processor (or researching which batches were best) and whether or not the Xbox's cheapo RAM will even work with a processor running at that speed, regardless of whether the FSB is set to something within traditionally stable ranges... Maybe I should start a thread on it.

Looks like I found a new obsession.

[dust08]

30 minutes ago, Prehistoricman said:

If RAM speed ever becomes an issue, you can reduce it by 33% by increasing the frequency divider from 2 to 3. On a normal Xbox, that reduces the clock from 200MHz to 133MHz.

The memory frequency divider is the '2' digit in the PLL register that usually has the value 0x00230801.

Oh well that's new information to me and would solve that problem, actually this could probably get much higher overclocks on a stock xbox as my hunch has been that memory is the main limit stopping higher clocks on the stock coppermines, although it could just be the FSB on the motherboard. How would one go about editing this register?

Edited October 9, 2022 by dust08

[Prehistoricman]

24 minutes ago, Bowlsnapper said:

Please forgive my stupidity, but could you clarify that a bit? I'm not as knowledgeable as I would like to be. If RAM speed becomes an issue when slowing down? I actually wasn't aware that you could control memory and CPU speeds independently from one another. Is this an option in XBOverclock? By divider, do you mean multiplier? JESUS I'm retarded.

dust08 has it right: if RAM speed becomes an issue when increasing the FSB too much, you can reduce the memory clock independently.

XBOverclock can be modified to do this. Go to its main.c file and after line 93 put bios_data[i+6] = 0x33; to reduce the memory clock by 33%.

[dust08]

1 minute ago, Prehistoricman said:

dust08 has it right: if RAM speed becomes an issue when increasing the FSB too much, you can reduce the memory clock independently.

XBOverclock can be modified to do this. Go to its main.c file and after line 93 put bios_data[i+6] = 0x33; to reduce the memory clock by 33%.

Awesome! My xbox is out of commission right now but when I get it back together and working I'll compile and test it. Do you know if it's possible to raise the memory clock as well? That could help downclocking a 1.4ghz box while keeping the memory speeds up if in fact that's an issue.

[Bowlsnapper]

19 minutes ago, Prehistoricman said:

dust08 has it right: if RAM speed becomes an issue when increasing the FSB too much, you can reduce the memory clock independently.

XBOverclock can be modified to do this. Go to its main.c file and after line 93 put bios_data[i+6] = 0x33; to reduce the memory clock by 33%.

OKay, well that's interesting. I wonder how hard the SL6BY (or any other 1.4, regardless of FSB spec) can be pushed without RAM limiting the FSB speed. I guess that would then be limited by how hard the CPU can be pushed on stock voltages. Taking that even further,I wonder how far voltages can be tweaked before needing PSU modifications. SO many questions.

Christ,I need a Computer Science degree.

[dust08]

3 minutes ago, Bowlsnapper said:

OKay, well that's interesting. I wonder how hard the SL6BY (or any other 1.4, regardless of FSB spec) can be pushed without RAM limiting the FSB speed. I guess that would then be limited by how hard the CPU can be pushed on stock voltages. Taking that even further,I wonder how far voltages can be tweaked before needing PSU modifications. SO many questions.

Christ,I need a Computer Science degree.

Also as far as voltages go there was a "pin mod" to tweak the voltages on the Tualatin you might wanna research if you really want to go all out on this. How that would work with the interposer is beyond me.

[Bowlsnapper]

11 minutes ago, dust08 said:

Also as far as voltages go there was a "pin mod" to tweak the voltages on the Tualatin you might wanna research if you really want to go all out on this. How that would work with the interposer is beyond me.

Are you talking about that wire mod linking two of the pins? Yeah, I saw that. Using it with an interposer (at least as far as fitting goes) wouldn't be an issue, as the CPU's pins are sitting on a PCB and have a fair amount of open space in there. However, I'm pretty sure that one of the interposer's functions is modifying voltage, as Coppermines (stock CPU) and Tualatins run on wildly different core voltages. So I'm not sure how THAT would come into play. I'm unclear on WHERE the best place to install a component to tweak voltage would be... because I don't know what I'm doing.

It seems that the SL6BY maxes out at about 1.8Ghz (1,750Mhz) at 1.525V. I cannot find ANY info about overclocking the SL64V.

[Bowlsnapper]

1 hour ago, dust08 said:

Oh well that's new information to me and would solve that problem, actually this could probably get much higher overclocks on a stock xbox as my hunch has been that memory is the main limit stopping higher clocks on the stock coppermines, although it could just be the FSB on the motherboard. How would one go about editing this register?

Yes, it IS the memory that causes lockups around 150Mhz or so. Certain revisions of the Samsung RAM went a bit higher, but not by much.

[coldasijs]

this sounds like good news for my 1.4 ghz xbox. I got it from zzattack and I had the plan to build it up as my one and only XBOX, although in reality I don't think I could get rid of my 1.6 :).

I already have an openxenium, so I can run 2 bios versions. I should start making time for my XBOX projects again