VOGONS


First post, by Sunken

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Hello there!

I rescued a lovely Elonex Lumina PC with a Cyrix MediaGX133 inside. I thought that was a great idea to have somewhat a "boosted 486" but it drives me crazy...

My first main issue is the integrated soundcard, an Xpressaudio16 which is a SB16 clone. I bought this PC mainly for playing again on Dune and the PC keeps crashing when taking an orni. I tried all the possible configurations (Port, DMA, IRQ, Disable DMA-Hi, etc...) but it keeps crashing. Tried on MS-DOS 6.22 and Windows 95. The only way to play is to disable Sounds FX and playing only music.

My second issue is the impossibility to add a soundcard as the riser is missing. I saw some Elonex Liminas with the riser but only on higher models ans a chinese clone named "Leo Oasis Data Computer". You can see the riser here at 11:00:
https://www.youtube.com/watch?v=hHpdJC97Q24

So, if you have tips to find a riser like this, take my money!

My last issue is about performances... Doom is so slow on DOS (probably 12-15 FPS MAX) but plays perfectly on Doom95. Even DOS Quake runs better... Probably due to the CPU architecture.

Thank you all for your help!

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Reply 1 of 7, by Falcosoft

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My last issue is about performances... Doom is so slow on DOS (probably 12-15 FPS MAX) but plays perfectly on Doom95. Even DOS Quake runs better... Probably due to the CPU architecture.

Since Cyrix CPUs have much better integer than floating point performance (compared to a similarly clocked Pentium) it's very unlikely that Doom (that uses integer math) performs worse than Quake (that uses floating point math) because of CPU architecture.
It's more likely that the Doom performance problem is related to the integrated VGA. Some VGA implementations do not like the planar/unchained Mode Y that Doom uses.
You should try FastDoom to determine if the problem is Mode Y or not. FDoom.exe uses Mode Y but FDoom13h.exe uses the more traditional Mode 13h so you can compare the performance of the 2 different modes.
https://github.com/viti95/FastDoom/releases
FastDoom. A new Doom port for DOS, optimized to be as fast as possible for 386/486 personal computers!

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Reply 2 of 7, by ViTi95

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Cyrix MediaGX SoC doesn't perform well under VGA mode Y/X, specially when lot's of OUT instructions are sent. FastDoom fixes this issue on modes 13h and VBE2. Also you can try other DOOM ports such as MBF (Marine's best friend) which also include support for additional video modes. Other option is to add an external PCI video card, bypassing the flawed one.

Edit: small video of my MediaGX (300MHz) comparing mode Y against mode 13h https://www.youtube.com/watch?v=3PAfvDsmzVY

Reply 4 of 7, by Sphere478

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A warning, please note to anyone reading this that these systems often use sockets that look like standard socket but they are wired completely different they may even say socket three? or socket seven on them but they are not. do not attempt to put a normal CPU in them it could fry everything.

Cool setup 😀
As for the riser,
If you can find a comprehensive pinout or a user that has one, it might be possible to replicate it it and order the pcb

Sphere's PCB projects.
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Sphere’s socket 5/7 cpu collection.
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SUCCESSFUL K6-2+ to K6-3+ Full Cache Enable Mod
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Tyan S1564S to S1564D single to dual processor conversion (also s1563 and s1562)

Reply 5 of 7, by rmay635703

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This is something I’ve wondered about is the timeline
Of the different packages and types of MediaGX chips vrs the corresponding cpu socket and release dates.

I strongly remember “MediaGX” talk before the official 97 release date back in 1996 and vaguely remember prototypes being evaluated at that time. I did discuss the chip in newsgroups prior to its release.
Later My Highschool had Compaq MediaGX/180s in the library internet lab which was my first reliable/ fast internet experience.

Most of my magazines and other bs from that time were tossed and I can find no run up discussion of the MediaGX before it’s release date which I find disappointing since I followed Cyrix quite closely mid to late 90’s

I am curious when the changeover to a pseudo socket 7 happened as it must have been early
And curious when Cyrix started sampling MediaGX engineering samples.

Reply 6 of 7, by darry

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An example of a "popular" MediaGX based system is the Compaq Presario 2200 . Looking up its history might help answer some questions. IMHO, running the stock Windows 95 install that it came with was borderline masochism, even by 1997/1998 standards .

MediaGX had decent SB16 compatibility, AFAICR, but had lackluster legacy VGA performance and borderline CPU performance . People were attracted by the low price, but "low" was an accurate qualifier for pretty much everything that thing had to offer . IMHO, MediaGX was a desperate attempt to milk the 486-compatible clone cash cow to the very last drop by integrating as much support logic as possible into the design to keep costs low while branding the thing as a valid "next generation" option . Again IMHO, getting a used high-end 486 would have been a better, cheaper and more flexible choice for pretty much any use case . The sole exception to this might have been the institutional thin client market, where cost trumps almost everything else .

In 2022 these machines are an interesting curiosity and possibly a viable and cheaper alternative to a 486, if one can live with the limitations .

That's my opinion, at least .

Reply 7 of 7, by MarkP

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Has the mobo manufactures documentation stated that chip is supported by it's chip set??

From memory their pin output was different than other Socket/Super Socket 7 systems. Even though they fit in those cpu socket.

Pentium fpu performance was way better.

Just pulled one from an old ACER Thin Client. There was a sticker over the plastic "Socket 7" cast marking stating "Cyrix GXMedia "