VOGONS


First post, by Robhalfordfan

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hello all

i was wondering something about socket 7 mobos and cpus

if my socket 7 mobo say in manual that the max it supports is 200mhz and split voltage etc
i taking into account the original release of mobo and cpu etc

would it be possible to put in higher clocked cpu of the time where it doesn't mention anything about it in mannal as long the voltage and fsb etc is set on mobo to match what the cpu, like say change from p200 mmx to p233 mmx

even though the manual doesn't say anything about that because the p233 mmx didn't exist yet at the time

would that ruined dos compatibility with some because its too fast

just an idea that crossed my mind

Reply 2 of 12, by dionb

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mpe wrote on 2020-06-26, 12:04:

For the 233MMX you just need a higher multipler.

If your board supports a 200MMX I would be surprised if the 233 wouldn't work.

Actually you don't need a higher multiplier for 233MHz, as Intel recycled the basic 1.5x setting (that every So5/7 board has) for 3.5x in the P55C. So if your board supports 200MMX it's always possible to run 233MMX. The only limitation is current - if the board has an old linear voltage regulator, it might be at its thermal limits at 200MHz. Then again, the difference between 200MMX and 233MMX is a measly 1.3W, so it's not likely to be a show-stopper.

More generally, for CPU support you need the following:
1) Core voltage. You can get away with minor overvolting (0.1 or 0.2V, with added cooling), but if your board can only do 3.3V and your CPU does 2.0V, forget it.
2) BIOS support. This has various shades of grey. Biggest issue is OEM BIOS refusing to boot with unknown CPU, but sometimes there are cache issues (Tillamook mobile MMX...) or other features not enabled if unsupported. If contemplating K6plus, take a look here for official and unofficial BIOS.
3) FSB+multipliers support. Least relevant, as the CPU will run of 1+2 are OK, but if you want to run a CPU designed for 4x100MHz on a board that can't support more than 2x66MHz, you're not going to get as much out of it as hoped.

Note that there is wiggle-room here:
- 1.5x multiplier is remapped to 3.5x in Pentium MMX and K6 and faster CPUs.
- 2x multiplier is remapped to 6x in later K6-2 and all K6-3 and K6plus CPUs.
- if your board lacks multiplier settings, you can hack them in: look at So7 pinout. Find BF2 (and BF1 if needed). Connect pin in socket (or on CPU) to a Vss=ground pin. Congratulations, you just unlocked the higher settings 😉
- FSB options depend on the PLL and on jumpers/switches. n jumpers give you 2^n options. So two jumpers give 4 options, three 8 etc. Frequently boards have undocumented settings. Set multiplier to lowest non-remapped setting and play around with the undocumented FSB options. With three jumpers you'll usually have 75MHz and 83MHz options. They overclock the PCI bus and connected devices (IDE!), but can be stable and if so help get a faster CPU. Take a K6-2 500 on an i430HX chipset board. At 66MHz FSB, it does max 6x66=400MHz. At 6x83 it will run at 500MHz. If you don't have the jumpers/switches, find the PLL chip and look up its data sheet. If it's capable of more, you might be able to hack an extra switch onto unused legs for those missing speeds. Or for real pro-level hacking, consider replacing the PLL. Take the Asus XP55T2P4. It's the ATX version of the legendary P55T2P4. Great board, particularly as last revisions have VRMs that can deliver 2.0V for K6plus CPUs. Unfortunately the XP55T2P4 PLL only goes up to 66MHz, where the P55T2P4 can do 83MHz. Swap PLLs and you can run those K6Plus CPUs at 500MHz 😀

Reply 3 of 12, by Tetrium

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Robhalfordfan wrote on 2020-06-26, 11:49:
hello all […]
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hello all

i was wondering something about socket 7 mobos and cpus

if my socket 7 mobo say in manual that the max it supports is 200mhz and split voltage etc
i taking into account the original release of mobo and cpu etc

would it be possible to put in higher clocked cpu of the time where it doesn't mention anything about it in mannal as long the voltage and fsb etc is set on mobo to match what the cpu, like say change from p200 mmx to p233 mmx

even though the manual doesn't say anything about that because the p233 mmx didn't exist yet at the time

would that ruined dos compatibility with some because its too fast

just an idea that crossed my mind

Your assumption about manuals often not including all possible upgrades is a correct one. These were often added on the manufacturers website.
Of course not all pages exist anymore, but google will be your friend here.
One website I kinda like is https://www.cpu-upgrade.com/
It includes even some AT style s7 boards.

DOS incompatibility has more to do with CPU speed and less so with whether or not the 233MHz P1MMX will work on your particular motherboard. It's somewhat like asking 2 separate questions even though things like cashes can also have an effect.

Whats missing in your collections?
My retro rigs (old topic)
Interesting Vogons threads (links to Vogonswiki)
Report spammers here!

Reply 4 of 12, by Robhalfordfan

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ok dokey

the only different i noticed between the p200 mmx and p233 mmx other than the higher clock speed is the multiplier as my p200 mmx has 3x multiplier and the p233 mmx needs a 3.5x multiplier otherwise everything else is the same (voltage, fsb etc)
looks like the manual doesn't say anything about 3.5x but i heard heard about 1.5x remapped to 3.5x but do all old mobos do it are is that kind of like a hit or miss, like s7 mobo was almost wild west like back then

i tried cpu-upgrade website and unfortunately my s7 mobo isn't there but i managed to find the mobo manufacturer website via wayback machine (slight nostalgia of 90s websites 😁) and again nothing about p233 mmx support

i am assuming there is no harm in trying as i can find that cpu for cheap and since the voltage and fsb etc are the same, just try messing about with the multiplier (prob a stupid thing to worry about but doubt it damage the cpu of mobo) and if it truly doesn't support it - never try, never know

no loss if it doesn't and could come it handy in the future for another project 😁

Reply 5 of 12, by Robhalfordfan

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mpe wrote on 2020-06-26, 12:04:

- if your board lacks multiplier settings, you can hack them in: look at So7 pinout. Find BF2 (and BF1 if needed). Connect pin in socket (or on CPU) to a Vss=ground pin. Congratulations, you just unlocked the higher settings 😉

the no multiplier settings in bios as all, its all on mobo with jumpers and don't know if have the confidence to try and hack it as scared in case i damage the cpu or mobo (or am i being silly 😁)

mpe wrote on 2020-06-26, 12:04:

- FSB options depend on the PLL and on jumpers/switches. n jumpers give you 2^n options. So two jumpers give 4 options, three 8 etc. Frequently boards have undocumented settings. Set multiplier to lowest non-remapped setting and play around with the undocumented FSB options. With three jumpers you'll usually have 75MHz and 83MHz options. They overclock the PCI bus and connected devices (IDE!), but can be stable and if so help get a faster CPU. Take a K6-2 500 on an i430HX chipset board. At 66MHz FSB, it does max 6x66=400MHz. At 6x83 it will run at 500MHz. If you don't have the jumpers/switches, find the PLL chip and look up its data sheet. If it's capable of more, you might be able to hack an extra switch onto unused legs for those missing speeds. Or for real pro-level hacking, consider replacing the PLL. Take the Asus XP55T2P4. It's the ATX version of the legendary P55T2P4. Great board, particularly as last revisions have VRMs that can deliver 2.0V for K6plus CPUs. Unfortunately the XP55T2P4 PLL only goes up to 66MHz, where the P55T2P4 can do 83MHz. Swap PLLs and you can run those K6Plus CPUs at 500MHz 😀

what is PLL

Reply 6 of 12, by Robhalfordfan

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i was wondering if this cpu http://www.cpu-world.com/CPUs/Pentium/Intel-E … FV80503266.html

would work in this build my first vintage pc build (DOS 6.22/Win 3.11/Win 95)

if not - what is the different between these two cpus - other than the part number

http://www.cpu-world.com/CPUs/Pentium/Intel-P … FV80503233.html
http://www.cpu-world.com/CPUs/Pentium/Intel-P … BP80503233.html

Reply 7 of 12, by jakethompson1

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Robhalfordfan wrote on 2020-09-12, 13:52:
i was wondering if this cpu http://www.cpu-world.com/CPUs/Pentium/Intel-E … FV80503266.html […]
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i was wondering if this cpu http://www.cpu-world.com/CPUs/Pentium/Intel-E … FV80503266.html

would work in this build my first vintage pc build (DOS 6.22/Win 3.11/Win 95)

if not - what is the different between these two cpus - other than the part number

http://www.cpu-world.com/CPUs/Pentium/Intel-P … FV80503233.html
http://www.cpu-world.com/CPUs/Pentium/Intel-P … BP80503233.html

The 266 is a laptop processor. I didn't think it came in a form that fits a desktop board.
If you get a 233, I think the best way forward is to configure your board for a Pentium MMX 200 and get everything working. Then, figure out which jumper is the multiplier and set that for a Pentium 100, but leave all other jumpers (esp. voltage) alone. That will bump you up from 200 to 233. Here are your jumper settings http://www.uncreativelabs.de/th99/m/A-B/34084.htm

Reply 8 of 12, by dionb

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Pentium 266MMX, Tillamook core, is a very interesting beast - but getting it working - with cache is pretty challenging. Here's the definitive thread about it: Tillamook 266MHz and working L2 cache?

Reply 9 of 12, by Robhalfordfan

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jakethompson1 wrote on 2020-09-12, 23:31:
Robhalfordfan wrote on 2020-09-12, 13:52:
i was wondering if this cpu http://www.cpu-world.com/CPUs/Pentium/Intel-E … FV80503266.html […]
Show full quote

i was wondering if this cpu http://www.cpu-world.com/CPUs/Pentium/Intel-E … FV80503266.html

would work in this build my first vintage pc build (DOS 6.22/Win 3.11/Win 95)

if not - what is the different between these two cpus - other than the part number

http://www.cpu-world.com/CPUs/Pentium/Intel-P … FV80503233.html
http://www.cpu-world.com/CPUs/Pentium/Intel-P … BP80503233.html

The 266 is a laptop processor. I didn't think it came in a form that fits a desktop board.
If you get a 233, I think the best way forward is to configure your board for a Pentium MMX 200 and get everything working. Then, figure out which jumper is the multiplier and set that for a Pentium 100, but leave all other jumpers (esp. voltage) alone. That will bump you up from 200 to 233. Here are your jumper settings http://www.uncreativelabs.de/th99/m/A-B/34084.htm

ok i thought that but wasn't sure as the manual doesn't mention anything about 233 (i imagine because the mobo came out before the 233 even existed)

since i am already using a mmx 200 in this build and jumpers are all set for it, it is only the multiplier that need to be changed

i thought the 266 was a laptop/mobile cpu hence the embedded part of it - but was playing devils advocate but wanted to be 100% sure

Reply 10 of 12, by Robhalfordfan

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dionb wrote on 2020-09-12, 23:59:

Pentium 266MMX, Tillamook core, is a very interesting beast - but getting it working - with cache is pretty challenging. Here's the definitive thread about it: Tillamook 266MHz and working L2 cache?

mmmm - had a look a at link and seems a bit fiddly and the Clock multiplier is 4x and the highest the mobo can go - as far as i know is 3x

Reply 11 of 12, by dionb

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Robhalfordfan wrote on 2020-09-13, 11:19:
dionb wrote on 2020-09-12, 23:59:

Pentium 266MMX, Tillamook core, is a very interesting beast - but getting it working - with cache is pretty challenging. Here's the definitive thread about it: Tillamook 266MHz and working L2 cache?

mmmm - had a look a at link and seems a bit fiddly and the Clock multiplier is 4x and the highest the mobo can go - as far as i know is 3x

3.5x multiplier is simple, just set 1.5x (100MHz) and a P55C (regular MMX) will interpret that as 3.5x.

266/300MHz on the Tillamook requires an extra, third, multiplier pin (BF2) of 4x / 4.5x. If you want to set that you have to manually connect the relevant pin to Vss/GND if your motherboard doesn't have a setting for it.

Reply 12 of 12, by Robhalfordfan

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dionb wrote on 2020-09-14, 05:55:
Robhalfordfan wrote on 2020-09-13, 11:19:
dionb wrote on 2020-09-12, 23:59:

Pentium 266MMX, Tillamook core, is a very interesting beast - but getting it working - with cache is pretty challenging. Here's the definitive thread about it: Tillamook 266MHz and working L2 cache?

mmmm - had a look a at link and seems a bit fiddly and the Clock multiplier is 4x and the highest the mobo can go - as far as i know is 3x

3.5x multiplier is simple, just set 1.5x (100MHz) and a P55C (regular MMX) will interpret that as 3.5x.

266/300MHz on the Tillamook requires an extra, third, multiplier pin (BF2) of 4x / 4.5x. If you want to set that you have to manually connect the relevant pin to Vss/GND if your motherboard doesn't have a setting for it.

ok thank you and will keep in mind, if i decide and/or find any but think 233 mmx is more common and more easy to find and set up but thank you