Cyrix DX50 is pretty rare, yes. It definitely exists, or those two reputable collectors couldn't and wouldn't have posted separate photos of it. Never seen one for sale, and I've been watching sales on CPU-World for well over a decade. Can't comment on integer or FP performance yet though, as I've not done my own tests (hope to get round to testing a few 486 boards and a broad selection of CPUs this year).

I see, that definitely makes sense. I figured insofar as that those collectors' photos were evidence of its existence, but have been wondering why they're so elusive; it seems as if the Cyrix DX-50 is up there in rarity with some of the true oddities of the 486 world like the UMC U5SD or Cyrix 5x86-133.

I can't lie that it's elusiveness definitely contributed some to my skepticism there.

Do you think that a Cyrix DX-40 might be able to cope with such an overclock, just to see the performance delta between that and an Intel DX-50?

Thanks for your thoughts, I really appreciate them! 😀

As long as it has a heatsink, I see no harm in trying to boot it at 50MHz. I certainly will be trying all my 486 at higher clocks, just to see which can cope.

I've definitely seen the Cyrix DX-50. I always found it amusing that Cyrix ever bothered with these. The Intel version was never that popular outside of engineering and academia, and seeing as how the market for the DX-50 was already basically dead in 1993 it didn't make any sense to clone it. I Could be mistaken, but didn't AMD also have a DX-50?

I won’t lie, the fact that Cyrix even considered a DX-50 intrigued me, and that’s really what prompted me to inquire. I feel as if the Intel DX-50 has a (somewhat deserved?) black sheep status amongst its peers and I figured a Cyrix equivalent would be even more interesting.

I can’t say I’ve seen an AMD DX-50, but that would be interesting! I wonder what stepping it’d have been, and on what process node it would have been fabbed? Perhaps it’d have shared a process with the early 5V DX2-80s and DX2-66s?

Out of curiosity, was there ever a Cyrix v50, as in a 3.3V DX-50? Now that would be an interesting CPU.

I just looked into it. AMD had the 40MHz DX, but sadly no 50.

Any evidence of those Cyrix DX-50 chips actually being available on the market back in the era?
Or was it just prototypes?

Grzyb wrote on 2022-01-05, 09:13:

Any evidence of those Cyrix DX-50 chips actually being available on the market back in the era?
Or was it just prototypes?

The two links in the original post show production models. Very uncommon though, I'd not heard of them before.

debs3759 wrote on 2022-01-05, 09:33:

Grzyb wrote on 2022-01-05, 09:13:

Any evidence of those Cyrix DX-50 chips actually being available on the market back in the era?
Or was it just prototypes?

The two links in the original post show production models. Very uncommon though, I'd not heard of them before.

Occasionally would notice them in the “big lists” of prices in the Computer Shopper usually with an ISA motherboard.

They arrived comparatively late and never made much sense to me, my guess is most folks felt the same so sales were low

Anonymous Coward wrote on 2022-01-05, 07:58:

I just looked into it. AMD had the 40MHz DX, but sadly no 50.

I see. Interesting. That probably makes sense, as the AMD DX-40 was not exactly the most well-regarded chip, by all accounts I’ve read.

rmay635703 wrote on 2022-01-05, 15:12:

debs3759 wrote on 2022-01-05, 09:33:

Grzyb wrote on 2022-01-05, 09:13:

Any evidence of those Cyrix DX-50 chips actually being available on the market back in the era?
Or was it just prototypes?

The two links in the original post show production models. Very uncommon though, I'd not heard of them before.

Occasionally would notice them in the “big lists” of prices in the Computer Shopper usually with an ISA motherboard.

They arrived comparatively late and never made much sense to me, my guess is most folks felt the same so sales were low

This makes sense to me. I pretty much figured the same.

I wonder if any of the early, high-end EISA 486 boards supported this CPU properly. That would be a pretty neat combination, and at least the 50MHz bus wouldn’t be much trouble on an EISA board.

WJG6260 wrote on 2022-01-02, 23:44:

Hello all, […]
Show full quote

Hello all,

I know this sounds like a foolish question, but I've been looking around here and there and have never seen a Cyrix DX-50 CPU. There's a few references out there to this particular CPU, namely on x86-guide here and on CPU-World here.

From what I understand--and from my personal experience--the Intel DX-50 is pretty fast, but the added wait states from the 50Mhz bus are somewhat disadvantageous when building such a system, especially if the motherboard is not up for the task of a 50Mhz bus. It seems like a well-tuned DX2-66 is just an all-around simpler, faster, and easier choice.

Cyrix 486s are another subset of oddities, in the sense that their off-cache accesses are quite fast, and their ALU performance is slightly less than that of their Intel/AMD counterparts. Their FPUs seem a little stronger though, at least from my rudimentary comparison of a 5V Cyrix DX2-80 to a 5v Am486DX2-80.

To that end, then, is it safe to presume that the Cyrix DX-50 is somewhere around an Intel DX-33 or AMD DX-40 in terms of sheer performance?

I feel like I've read something to the extent that the early Cyrix 486s post-Fascache models (Is it "M6," for the full 8k cache Cx486DXs?) had heat issues, and that's why the 4.0V and 3.6V models are more common, as they supplanted those earlier, hotter models. Is the Cyrix DX-50 then a pretty rare bird?

Thanks for the input, and I hope you all had a wonderful holiday and New Year!

Yes, it exist. And I have one in a socket 3 motherboard and working!
I have had many troubles to make it work correctly.
Sometimes the mouse didn't work, or i have troubles with the video card, i put Windows 3.1, and Dos 6.22 and an adapter from MicroSD to Ide as a harddisk.
This Cyrix work with 5 V

Anonymous Coward wrote on 2022-01-05, 07:58:

I just looked into it. AMD had the 40MHz DX, but sadly no 50.

These tend to overclock to 50. I had Am486DX 40 and it ran well on 50MHz back in the day.

Cheers,

WJG6260 wrote on 2022-01-06, 16:00:

I see. Interesting. That probably makes sense, as the AMD DX-40 was not exactly the most well-regarded chip, by all accounts I’v […]
Show full quote

Anonymous Coward wrote on 2022-01-05, 07:58:

I just looked into it. AMD had the 40MHz DX, but sadly no 50.

I see. Interesting. That probably makes sense, as the AMD DX-40 was not exactly the most well-regarded chip, by all accounts I’ve read.

rmay635703 wrote on 2022-01-05, 15:12:

debs3759 wrote on 2022-01-05, 09:33:

The two links in the original post show production models. Very uncommon though, I'd not heard of them before.

Occasionally would notice them in the “big lists” of prices in the Computer Shopper usually with an ISA motherboard.

They arrived comparatively late and never made much sense to me, my guess is most folks felt the same so sales were low

This makes sense to me. I pretty much figured the same.

I wonder if any of the early, high-end EISA 486 boards supported this CPU properly. That would be a pretty neat combination, and at least the 50MHz bus wouldn’t be much trouble on an EISA board.

Here are another photos:

Jujoba wrote on 2023-12-20, 23:20:

WJG6260 wrote on 2022-01-06, 16:00:

I see. Interesting. That probably makes sense, as the AMD DX-40 was not exactly the most well-regarded chip, by all accounts I’v […]
Show full quote

Anonymous Coward wrote on 2022-01-05, 07:58:

I just looked into it. AMD had the 40MHz DX, but sadly no 50.

I see. Interesting. That probably makes sense, as the AMD DX-40 was not exactly the most well-regarded chip, by all accounts I’ve read.

rmay635703 wrote on 2022-01-05, 15:12:

Occasionally would notice them in the “big lists” of prices in the Computer Shopper usually with an ISA motherboard.

They arrived comparatively late and never made much sense to me, my guess is most folks felt the same so sales were low

This makes sense to me. I pretty much figured the same.

I wonder if any of the early, high-end EISA 486 boards supported this CPU properly. That would be a pretty neat combination, and at least the 50MHz bus wouldn’t be much trouble on an EISA board.

Here are another photos:

Some nice pics of the CPU. You should perhaps run some benchmarks from Phil's DOS benchmark pack. However, you'll probably then need a VLB graphics card for faster performance (with some wait states applied).

Nice ! Understand the issue with getting it to work well with other parts....yep need a good VLB card to run some tests...
Have a 5x86-100GP (not that rare) that can run at 50Mhz clock but is 3.3v and in an Aries97 interposer, worked ok in the board I pulled it from but was using the 3x mult not the 2x (wouldn't boot proper iirc)

Jujoba wrote on 2023-12-20, 21:52:

[...]

I have had many troubles to make it work correctly.
Sometimes the mouse didn't work, or i have troubles with the video card, i put Windows 3.1, and Dos 6.22 and an adapter from MicroSD to Ide as a harddisk.

The interesting question: were these CPU-specific or just regular issues with 50MHz bus (i.e. you would have had same issues with i486DX-50, or with an Am486DX-40 overclocked to 50MHz)?

50MHz VLB would be insane. Just pre VLB some manufacturers released 50MHz local bus graphics systems, but everything was soldered on the board. Example Re: Pre-VESA Proprietary 32-bit Local Buses?
May 1992 "Swan 486/33 DB, The blinding speed of Swan Direct Bus" with S3 86c911. CPU and graphic chip on a single, separate PCB daughterboard.
PC Mag 12 May 1992 https://books.google.pl/books?id=jcrsPJb76HAC … irect+local+bus
June Swan 486/50 DB running S3 86c924 at 50MHz
PC Mag 30 Jun 1992 https://books.google.pl/books?id=uummfdS7yF8C … local+bus+50mhz

I have a Chicony CH-471A socket 3 motherboard with an Intel 486DX 50 MHz (not 486DX2-50) CPU installed and it's running fine at a 50 MHz FSB with an S3 805 VLB graphics card.
You obviously have to apply slower wait states in the CMOS setup to ensure that your system is running stable at that speed. Some motherboards (and VLB graphics cards) also had jumpers that could be set to select between a 0 or 1 wait state.

rasz_pl wrote on 2023-12-21, 12:41:

50MHz VLB would be insane. Just pre VLB some manufacturers released 50MHz local bus graphics systems, but everything was soldere […]
Show full quote

50MHz VLB would be insane. Just pre VLB some manufacturers released 50MHz local bus graphics systems, but everything was soldered on the board. Example Re: Pre-VESA Proprietary 32-bit Local Buses?
May 1992 "Swan 486/33 DB, The blinding speed of Swan Direct Bus" with S3 86c911. CPU and graphic chip on a single, separate PCB daughterboard.
PC Mag 12 May 1992 https://books.google.pl/books?id=jcrsPJb76HAC … irect+local+bus
June Swan 486/50 DB running S3 86c924 at 50MHz
PC Mag 30 Jun 1992 https://books.google.pl/books?id=uummfdS7yF8C … local+bus+50mhz

Basically the calculation is:
50 MHz --> 0 VLB slots (just one onboard device)
40 MHz --> 1 VLB slot
33 MHz --> 2 VLB slots
25 MHz --> 3 VLB slots

It may be possible to add one VLB slot, but that is out of spec then. If you want to go borderline you even may try to run 3 VLB slots at 40 MHz.

Jujoba wrote on 2023-12-20, 21:52:

Yes, it exist. And I have one in a socket 3 motherboard and working! I have had many troubles to make it work correctly. Sometim […]
Show full quote

Yes, it exist. And I have one in a socket 3 motherboard and working!
I have had many troubles to make it work correctly.
Sometimes the mouse didn't work, or i have troubles with the video card, i put Windows 3.1, and Dos 6.22 and an adapter from MicroSD to Ide as a harddisk.
This Cyrix work with 5 V

Even an empty VLB slot raises the capacity on the Bus. Perhaps this may cause troubles even if you don't use a VLB card.

Does your Cx486DX-50 run its cache in write through or write back mode?