i don't know of any.
all intel and most amd(8kb cache) have locked multiplier.
amd enhanced 486dx2/dx4(16kb) can run at 2x and 3x.
amd5x86 can run at 3x and 4x.

To get Cyrix 5x86 into 1X mode you need to use a software utility. I think you can also trick it into 1X mode by toggling it from 3X to 2X mode when the system is running.

noshutdown wrote:

i don't know of any. all intel and most amd(8kb cache) have locked multiplier. amd enhanced 486dx2/dx4(16kb) can run at 2x and 3 […]
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i don't know of any.
all intel and most amd(8kb cache) have locked multiplier.
amd enhanced 486dx2/dx4(16kb) can run at 2x and 3x.
amd5x86 can run at 3x and 4x.

I remember reading somewhere that an Intel Pentium Overdrive might be able to use 1x multi when its fan gets disabled..? Apparently, it downclocks for safety to prevent itself from overheating.

Anonymous Coward wrote:

To get Cyrix 5x86 into 1X mode you need to use a software utility. I think you can also trick it into 1X mode by toggling it from 3X to 2X mode when the system is running.

That's good to hear. Do you know which utility I need? Thanks in advance.

Yeah, I think you're right about the POD83 and the fan connector.

The utility for Cyrix 5x86 that I use is CTCHIP. I think Peter Moss Utility can do it too.

Or the Evergreen 5x86 DOS utility, but you will need to convert from 8-bit binary to HEX. Not a big deal, but it is an extra step.

The latest, but yet unreleased, SetMul does the switching to 1x as well. Pending is the writing of a Cyrix 5x86 CPU detection routine...
All my retro hardware is in external storage, so I cannot work on it for now. maybe in 2 months.

The Cyrix 5x86 1x mode is very useful, the main reason I now prefer this CPU over the intel DX4-100MHz.

What about Cyrix 6x86 and MII?

feipoa wrote:

What about Cyrix 6x86 and MII?

The Cyrix 6x86 and 6x86L do run with a 1.0x multiplier, when the multiplier jumpers are set accordingly. The 6x86MX and MII do not.
Last year I studied most Socket 7 and Slot 1 / Socket 370 related Datasheets, in the quest to find interesting CPU registers to toggle. The 6x86/MII datasheets do not mention a 5x86-like software clock adjustment. 🙁

Have you thought about adding multiplier functionality to SetMul for Cyrix 6x86/MII CPUs?

feipoa wrote:

Have you thought about adding multiplier functionality to SetMul for Cyrix 6x86/MII CPUs?

I tried to say, there is no way to do that. 6x86/MII will only set the multiplier based on jumper signals at boot. It does not have corresponding CPU registers. At least, no documented ones.

Have you tried experimenting with some of the "reserved" bits in CCR0-5? I seem to recall a Windows-based program called Rain which would slow down the clock of Cyrix 5x86/6x86 CPUs when they are idle.

I experimented a little with both the 5x86 and 6x86 registers using the IBM utility, but I can't remember to what extend.
Rain supposedly only uses the HLT instruction for power saving effect.

Anonymous Coward wrote:

Yeah, I think you're right about the POD83 and the fan connector.

The utility for Cyrix 5x86 that I use is CTCHIP. I think Peter Moss Utility can do it too.

Got some time to play around with some of these CPUs and utilities. I can confirm the Intel POD83 clocks at 1x multi with its fan removed, and 2.5x multi with its fan attached (managed 100MHz at 40x2.5). Should be able to rig a switch to flick between high/ low multipliers...

BTW, I can't get CTCHIP to work. This utility seems to be limited by motherboard chipsets - it doesn't recognise the Opti chipset on my board.

feipoa wrote:

Or the Evergreen 5x86 DOS utility, but you will need to convert from 8-bit binary to HEX. Not a big deal, but it is an extra step.

After trying a few utilities, this Evergreen one seems to be the most flexible. I've been using trial and error, but can't seem to change the multi from 3x on my Cyrix 5x86. Do you know which registers I need to change for 1x, 2x and 3x multi? An example would be great.

Whilst trying to figure this out using ET586.EXE, I've managed to accidently change the FSB from 33MHz to both 11MHZ and 10MHz by modifying the PCR0 and PMR registers - I didn't even know this was possible with the Cyrix. The ETDIAG.EXE utility is reporting these low FSBs. Are there any documents outlining what all these registers do when using this Evergreen utility?

gerwin wrote:

The latest, but yet unreleased, SetMul does the switching to 1x as well. Pending is the writing of a Cyrix 5x86 CPU detection routine...

I did a quick test with Setmul, and as expected, the Cyrix 5x86 isn't recognised. Setmul is working great with my K6-III+ though, so looking forward to the updated version...

Read these:

http://datasheets.chipdb.org/Cyrix/5x86/5X-ABDB.PDF
and
http://datasheets.chipdb.org/Cyrix/5x86/5XBIOSGD.PDF

The multiplier alteration register is well documented.

The CTCHIP 5x86 utility is NOT chipset specific. Does your copy of CTCHIP have CX586.CFG?

@feipoa: Thanks for the links - I'll check those out.

@ Anonymous Coward: When I run "CTCHIP34.EXE", or "CTCHIP34.EXE /? "at the command promt, I keep getting an error message in German, saying something like it cannot find .CFG file.

And when I look at the contents of the directory, there are a bunch of files named like 'motherboard-chipsets.cfg'... and my Opti chipset isn't present. What's the usage syntax for this executable? Do I need to run CTCHIP34.EXE with the CX586.CFG file? Looking at the directory, I do see that file amongst all the other 'chipset.cfg' files...