StriderTR wrote on 2024-12-10, 09:09:

I have an IBM branded PR166+ in my current DOS build, may drop this one in there to test it, and if it works, it's a bit faster. Though for most DOS games I play, the current PR166 (133MHz) is good enough. 😜

DOS Build: https://theclassicgeek.blogspot.com/2024/02/a … s-3x-retro.html

Your build use very similar motherboard to mine: ATC-5020+. I have started my projekt from 6x86 PR150 (120 Mhz), but then i get 6x86 PR266 (I used it as 225 and 233 Mhz -perfectly stable) and now i have MII-333GP 3x83 Mhz (but i use it as 3,5x75 MHz - 263 MHz because my motherboard don't have 83 fsb option). This 333 is max what this motherboard can handle and it fits perfect for my nostalgic hardware and software requirements 1996-1999 😀

The PLL on Your Motherboard has the ability to do 83mhz but You would need to modify the motherboard I suspect.

In my thus far limited testing, more like general screwing around, I have thought that, whichever way you like to say it, the MX and MII don't suffer much from lower bus, or don't appear to gain much from higher bus, due to that generously large 64kB cache. Though that possibly ceases to be the case as you get close to 300mhz.

Imperious wrote on 2024-12-11, 00:29:

The PLL on Your Motherboard has the ability to do 83mhz but You would need to modify the motherboard I suspect.

Thanks for that info, i will check it out. But my current setup with 75 MHz works perfectly fine for me - cpu runs stable at 263 MHz on stock voltage. I doubt that it go up to 290 MHz on 83 bus because this cpu has production stamps of November 98. As BitWrangler said higher FSB don't change much in Cyrix MII case. Higher core frequency is more important to put more life in fpu 😀

Just for fun, some days ago I tested two Cyrix 6x86L (M1) PR200+ about their OC-potential: one made by Cyrix and one made by IBM.

Using air cooling, both of them run stable at 200 MHz (FSB 100 MHz and 3,5 Vcore - yes, they still seems to accept it in accordance to the earlier non-L-models, even they run normally at 150 MHz/2,8 Vcore as L-model).

Both CPUs are able to run !NOT STABLE IN WINDOWS! at 210 MHz (FSB 105 MHz), too, so here are for instance the results for this frequency, as this was the highest possible I was able to reach, just to show the theoretical potential of those CPUs.

The rest of the hardware: GA-5AX (Rev. 4.1, 512 KB L2), ATI Radeon 7500 (AGP 2x on this board), 1x 256 MB RAM PC-133,CL3 @ PC105, CL2.

BTW, in case of 210 MHz, the POST shows still 200 MHz only.

next pics

and the last pics

Finally, it can be seen the poor FPU-performance (and the good Integer-performance), as this is usual for those CPU-models.

Only Cyrix CPU I have is this "value-oriented" one that I also don't seem to have a board for. Probably went out as e-waste years ago.

OVERK|LL wrote on 2025-02-01, 15:25:

Only Cyrix CPU I have is this "value-oriented" one that I also don't seem to have a board for. Probably went out as e-waste years ago.

Very nice CPU.
This is a Cyrix-CPU called "Media-GX". It is fully pin-compatible to the Socket 7 (Intel Pentium 1) - but it is NOT electrical compatible with this socket, so please do NOT use it with such a board.
This kind of CPU needs a spetial socket made espetially (and only) for it - they are very rare in the last years, so you will need a lot of luck to get one.
As far as I know, this was the first combined chip on the mainstream-market with an integrated VGA-chip "on die" next to the CPU-chip (e.g. similar to the Intel-iCore-Generation many years later).

gonzo wrote on 2025-02-05, 15:57:

Very nice CPU. This is a Cyrix-CPU called "Media-GX". It is fully pin-compatible to the Socket 7 (Intel Pentium 1) - but it is N […]
Show full quote

OVERK|LL wrote on 2025-02-01, 15:25:

Only Cyrix CPU I have is this "value-oriented" one that I also don't seem to have a board for. Probably went out as e-waste years ago.

Very nice CPU.
This is a Cyrix-CPU called "Media-GX". It is fully pin-compatible to the Socket 7 (Intel Pentium 1) - but it is NOT electrical compatible with this socket, so please do NOT use it with such a board.
This kind of CPU needs a spetial socket made espetially (and only) for it - they are very rare in the last years, so you will need a lot of luck to get one.
As far as I know, this was the first combined chip on the mainstream-market with an integrated VGA-chip "on die" next to the CPU-chip (e.g. similar to the Intel-iCore-Generation many years later).

Yeah, boards compatible with it seem to be rarer than hens teeth and I'm of course not even sure the CPU is good, since I have no way of testing it.

OVERK|LL wrote on 2025-02-05, 18:42:

gonzo wrote on 2025-02-05, 15:57:

Very nice CPU. This is a Cyrix-CPU called "Media-GX". It is fully pin-compatible to the Socket 7 (Intel Pentium 1) - but it is N […]
Show full quote

OVERK|LL wrote on 2025-02-01, 15:25:

Only Cyrix CPU I have is this "value-oriented" one that I also don't seem to have a board for. Probably went out as e-waste years ago.

Very nice CPU.
This is a Cyrix-CPU called "Media-GX". It is fully pin-compatible to the Socket 7 (Intel Pentium 1) - but it is NOT electrical compatible with this socket, so please do NOT use it with such a board.
This kind of CPU needs a spetial socket made espetially (and only) for it - they are very rare in the last years, so you will need a lot of luck to get one.
As far as I know, this was the first combined chip on the mainstream-market with an integrated VGA-chip "on die" next to the CPU-chip (e.g. similar to the Intel-iCore-Generation many years later).

Yeah, boards compatible with it seem to be rarer than hens teeth and I'm of course not even sure the CPU is good, since I have no way of testing it.

I have a Presario 2200 with a MediaGX 120 (P150+) and it's very very slow. Only slightly faster than a 486. It has an ISA VGA card on-board and there's no PCI expansion slots so that reinforces the 486 feeling. 3DBench 25. With a fast VGA card the experience would be different, maybe closer to a slow Pentium.

Has anyone removed a heatsink from a Cyrix 5x86 chip that has the heatsink already on them from the factory successfully?

Is the chip underneath the same as any other non-heatsink'd 5x86?

Don't know about success, but if it's like other epoxied chips of the era, cold makes it brittle. One cold or should twist off relatively easily.

Twist. Not lever.

Gotcha.

Safe to assume that the Heatsink'd Cyrix 5x86 chips are just regularly marked chips underneath the heatsink?

I'm pretty sure there are no markings under the heatsinks.

Tiido wrote on 2025-02-06, 06:37:

I'm pretty sure there are no markings under the heatsinks.

I've removed a green heatsink from a Cyrix 5x86. The chip was marked as:

Cyrix
5x86
5x86-100GP

No voltage or multiplier markings.

I have another chip which has the characteristic silhouette markings of the diamond shaped mesh structure from the heatsink's thermal pad. This chip was marked:

Cyrix
5x86
5x86-100GP/4X

feipoa wrote on 2025-02-06, 07:34:

I've removed a green heatsink from a Cyrix 5x86. The chip was marked as: […]
Show full quote

Tiido wrote on 2025-02-06, 06:37:

I'm pretty sure there are no markings under the heatsinks.

I've removed a green heatsink from a Cyrix 5x86. The chip was marked as:

Cyrix
5x86
5x86-100GP

No voltage or multiplier markings.

I have another chip which has the characteristic silhouette markings of the diamond shaped mesh structure from the heatsink's thermal pad. This chip was marked:

Cyrix
5x86
5x86-100GP/4X

What method did you use to remove the heatsink safely?

Ok, interesting, so there are markings to expect underneath the heatsink.

If it is epoxied, freeze + twist works good. If it is just some sticky thermal pad, then heating (50ºC+) will make the glue soft enough that it will come off without too much struggle.

I don't recall what I removed the heatsink with, it was 20 years ago, but I still have the CPU and the heatsink. Normally you'd start with the least invasive, so freeze the CPU then tap the side of the heatsink with a hammer. You can also take a fresh razer blade and tap it into the slot between the heatsink and the CPU.

If I recall, the thermal pads on these CPUs have a flat aluminium layer in the middle of the thermal pad, but I may be confusing it with the TI SXL heatsinks, which look identical.

OVERK|LL wrote on 2025-02-05, 18:42:

Yeah, boards compatible with it seem to be rarer than hens teeth and I'm of course not even sure the CPU is good, since I have no way of testing it.

Well, today I dig out the only appropriate board I have: a SuperTek ST-MGXm3A (chipset is a Cyrix 5530 GXm).
I have some Media-GX-CPUs here from Cyrix and from National Semiconductor (NSC; made with Cyrix-license).

Will try to set-up a Windows-system the next days. Still no idea if it works, or not.