Cyrix Instead - Desktop Build

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Cyrix Instead - Desktop Build

Postby foey » 2015-11-26 @ 21:25

Hey all,

I've not been doing much retro recently due to work and family commitments however I stumbled on a brand new/un-used desktop case which was not far from where I was working a week back on ebay. I popped in and picked it up for the pricey sum of ... 50p.

Now it left me with a dilemma, what to build in it? I've got Pentium MMX, K6-2, Athlon K7, Pentium III & Pentium 4 builds already nested away. So went through my parts and found it!

Image

I'd build a Cyrix DOS based machine. I have a number of socket 7 boards but ended up going for the Abit AB-PX5 due to it's 430 Chipset and the easy CPU clock selector in the bios.
The Cyrix processor in question is a Cyrix 6x86-PR166+ which was meant to compete directly with the Pentium 166 as a much cheaper alternative. Although rated at 166 (PR Rating) it runs at 133mhz.

So onto the build. The internals of the case has some terrible sharp edges, after an few minutes of building my hands were covered in cuts. I don't know if you can see but the top rail I actually covered with some black electrical tape to soften it! It was quite roomy inside.

Image

Being a ATX case I used a ATX to AT converter and mounted the switch on the rear as I didn't want to mess with the pre-installed power button on the front (Cheaply made case!) I've also mounted the PS2 onto the case as I hate using the risers as they always tend to bend.

Image

My brand new, un-used socket 7 cooler in action cooling the Cyrix. Apparently rated up to 1.4Ghz - can you imagine cooling a 1.4 Athlon Thunderbird :lol:

Image

Case needs a Cyrix Badge :happy:

Image

Available speeds selectable :- PR120, PR133, PR150, PR166 (Currently being used) & PR200 (Yes, it does run without any issues at this speed)

Image

Specifications

Cyrix 6x86-PR166+ (133mhz) Processor
32mb SD-RAM
Abit AB-PX5, Intel 430 Motherboard
4mb ATi Rage IIC (Mach64) PCI Graphics Card
Creative AWE64 Value (CT4500) Sound Card
48x Compaq CD-ROM / Using QCD to limit to 4x
Seagate 4.3Gb ATA Hard Drive
Intel 100 PCI NIC (From 1996)
Windows 95c with Plus Pack
DELL ATX 250w Power Supply

Overall I'm happy, part of me wants to get a more period correct CD-ROM drive - then again QCD solves the noise issue and it reads everything including CD-RWs. I need to get a floppy drive, currently only have black ones spare.

I need to swap out the ATi card at some point, whilst the quality is clear, it's very noisy - almost like your using a poor quality pass through cable.

I do have a Intel Pentium MMX 200mhz staring at me on the desk, whilst it would be much quicker (Esp in games such as Quake) I already have a MMX233 AT build. It's something about it being different :happy:
Cyrix Instead Build, 6x86 166+ | 32mb SD | 4mb S3 Virge DX | Creative AWE64 | Win95
ATC-S PIII Tualatin Win9x Build :- http://www.vogons.org/viewtopic.php?f=25&t=40248
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Re: Cyrix Instead - Desktop Build

Postby brassicGamer » 2015-11-26 @ 23:03

Nice idea. I think if you have a Cyrix part then it's nice to use it but I think most people looking to build a socket 7 machine would go AMD or Intel because of availability nowadays. I have this same CPU but have never used it. I understand the pipeline was more efficient on the Cyrix models which is why it could complete more instructions per cycle, thereby performing akin to a faster-clocked Intel part. Are there any other benefits to using Cyrix?
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Re: Cyrix Instead - Desktop Build

Postby feipoa » 2015-11-27 @ 05:03

foey wrote:Being a ATX case I used a ATX to AT converter and mounted the switch on the rear as I didn't want to mess with the pre-installed power button on the front (Cheaply made case!)

You can use your existing case button on that motherboard if you follow the circuit I made for a similar build. The circuit converts a momentary ATX power button to that of a latching AT style power button. viewtopic.php?t=31525

You should also create an AT-to-ATX I/O shield.

What is that turbo frequency option in the BIOS for?
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Re: Cyrix Instead - Desktop Build

Postby gdjacobs » 2015-11-27 @ 05:55

Better to use an edge triggered TTL JK flip flop. All preset and clear options are wired to be inactive, J and K are wired to toggle, and clock is fed by the pushbutton. You can insert a MOV or Zener as well as current limiting resistors if you want to get more fancy.
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Re: Cyrix Instead - Desktop Build

Postby feipoa » 2015-11-27 @ 06:06

gdjacobs wrote:Better to use an edge triggered TTL JK flip flop. All preset and clear options are wired to be inactive, J and K are wired to toggle, and clock is fed by the pushbutton. You can insert a MOV or Zener as well as current limiting resistors if you want to get more fancy.

Could you present a schematic of your design which is proven to work for this intended purpose? I do not understand why you think using a flip-flop is better than the design I presented. I started off thinking I was going to use a flip flop for this design decided my bin of desoldered BJT's wouldn't get used otherwise.
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Re: Cyrix Instead - Desktop Build

Postby gdjacobs » 2015-11-27 @ 07:43

Everyone's free to do their own implementation. I'm certain it could be done purely with electromechanicals -- whatever floats your boat. I like J-K better simply because of the simpler implementation. At it's core, we're talking one dip chip and a pull up resistor.

I've used circuits like this in the past, although I haven't proven this particular example in a test circuit. As such, there may be some slop and error.
Image

Another option is to use a basic DIP pack micro for the logic. There's a youtube video featuring this approach, although I can't locate it at the moment (Phil might have the link). It allows preservation of state logic and auto power on.
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Re: Cyrix Instead - Desktop Build

Postby feipoa » 2015-11-27 @ 08:00

That certainly would require less soldering! However, I do not anticipate any functional advantage. My circuit did require some optimisation of resistor values, however the values I have presented in the schematic are tried and true. I haven't had one hickup with operation in hundreds of power cycles. Unfortunately, I do not have a JK flip-flop to test this with.
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Re: Cyrix Instead - Desktop Build

Postby gdjacobs » 2015-11-27 @ 08:27

Agreed, functionally no different. Like you, I'm afraid I don't have a J-K on hand (and not enough NAND or NOR logic to build one).
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Re: Cyrix Instead - Desktop Build

Postby foey » 2015-11-27 @ 11:19

brassicGamer wrote:Nice idea. I think if you have a Cyrix part then it's nice to use it but I think most people looking to build a socket 7 machine would go AMD or Intel because of availability nowadays. I have this same CPU but have never used it. I understand the pipeline was more efficient on the Cyrix models which is why it could complete more instructions per cycle, thereby performing akin to a faster-clocked Intel part. Are there any other benefits to using Cyrix?


The Cyrix 6x86 appears to be quicker in most "business" benchmarks at the time than the Pentium where integer performance was key however Cyrix struggled on its floating point performance which compared to the Pentium was mediocre.

I did a very quick test last night. I plugged in a Pentium MMX 200 and set it as a 166 processor. Then then benchmarked Quake - which was primary built around the Pentiums very strong floating point operations.

320 x240 (*I think, as I upped the resolution)

Cyrix PR166+ - 20.1 fps
Intel Pentium MMX 166mhz - 33.5 fps

If I get any time, I'll try and clock the Pentium at 133mhz and run the test again.

feipoa wrote:You can use your existing case button on that motherboard if you follow the circuit I made for a similar build. The circuit converts a momentary ATX power button to that of a latching AT style power button. viewtopic.php?t=31525

You should also create an AT-to-ATX I/O shield.

What is that turbo frequency option in the BIOS for?


Yes, need to find a blank. I seen a couple of people cutting out their own holes?

Good Question, taken from the manual :-

The increase by 2.5% of the CPU speed is not a standard feature of this product. It is only for use by our development department to verify that the CPU is able to work normally when CPU speed, operating temperature and power supply are 2.5% higher or lower than the standard values. This is to guarantee product stability. We require the manufacturer of the Clock Generator to meet the demands of our development department and to add a TURBO Frequency feature used for testing purposes by our R&D department. Of course, you can use this feature to test the stability of your own system, but after you have tested the product, we recommend that you set it back to its normal value in order to guarantee system stability.

The Turbo mode allows you to speed up the external clock byapproximately 2.5%. This feature is used to verify the design flexibility.It is a very important tool for test units to verify CPU stability. Do not use this feature.

Disable: CPU external clock is operating within the normal limits.
Enable: CPU external clock is operating within the limits of the Turbo mode.


It makes no difference on the Cyrix Processor, assuming due to CPUID being disabled by default. However I've tested the feature on the Intel Pentium MMX 200, set at 166mhz and it increased the clock speed to 177mhz (Verified in speedsys) It seemed to be stable.
Cyrix Instead Build, 6x86 166+ | 32mb SD | 4mb S3 Virge DX | Creative AWE64 | Win95
ATC-S PIII Tualatin Win9x Build :- http://www.vogons.org/viewtopic.php?f=25&t=40248
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Re: Cyrix Instead - Desktop Build

Postby bjt » 2015-11-27 @ 11:54

Nice machine, it's pretty much the same spec as my first home-built PC. I had an ATI Mach64 and a VX chipset board.
Later on I tried overclocking the Cyrix (bad idea...) and killed the VCore VRM on the motherboard. It still worked with non-MMX CPUs though :lol:
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Re: Cyrix Instead - Desktop Build

Postby BSA Starfire » 2015-11-27 @ 12:03

Great stuff, I use a 6x86 in a DOS build myself, have tested many speed grades of Cyrix/IBM from 150+ to MX 300, all on a Intel TX based board.
You might find this optimiser for the Cyrix CPU's useful, I found it made a real difference in performance with both the M1 & M2.
http://www.helsinki.fi/~mpjohans/6x86opt/
All the best!
Chris
386SX 33MHz,4MB Ram,ALi M1217 motherboard,OAK OTI077 1MB. Seagate ST1144A.
386DX 25MHz,IIT 387,8MB RAM,Opti,32K cache,WDC90C30 512K.Conner CF170A.
IDT Winchip C6 200MHz,DFi P5BTX/L,Number Nine S3 ViRGE 2MB,SoundBlasterCT2260,1.2Gb Fujitsu.
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Re: Cyrix Instead - Desktop Build

Postby foey » 2015-11-27 @ 12:07

BSA Starfire wrote:Great stuff, I use a 6x86 in a DOS build myself, have tested many speed grades of Cyrix/IBM from 150+ to MX 300, all on a Intel TX based board.
You might find this optimiser for the Cyrix CPU's useful, I found it made a real difference in performance with both the M1 & M2.
http://www.helsinki.fi/~mpjohans/6x86opt/
All the best!
Chris


Thanks Chris,

I actually installed that tool last night, when enabled it actually slowed the machine down - so I took a couple of switches off and enabled CPUID and performance went back up to normal.

What switches do you have in your Autoexec/Config sys for the tool? - I was going to have a play tonight.
Cyrix Instead Build, 6x86 166+ | 32mb SD | 4mb S3 Virge DX | Creative AWE64 | Win95
ATC-S PIII Tualatin Win9x Build :- http://www.vogons.org/viewtopic.php?f=25&t=40248
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Re: Cyrix Instead - Desktop Build

Postby BSA Starfire » 2015-11-27 @ 12:27

Not home right now so working from memory(never a good thing), think i left in on defaults pretty much, just specified the video RAM size for the linear frame buffer. If you enable the CPUIDEN i do remeber that Speedsys ceases to work, it locks up during reading the machine specs.
Quake is just not a fair test for any non Intel CPU in mu opinion, as you said yourself it was hand coded specifically for the Pentium so all the rest come up short, I'm sure if it had been written/optimised for the 6x86 or K5 then the pentium would have looked like a dog.
Best,
Chris

Thread here you might find useful too, I asked the same questions about 6x86 opt.
viewtopic.php?f=46&t=45252
386SX 33MHz,4MB Ram,ALi M1217 motherboard,OAK OTI077 1MB. Seagate ST1144A.
386DX 25MHz,IIT 387,8MB RAM,Opti,32K cache,WDC90C30 512K.Conner CF170A.
IDT Winchip C6 200MHz,DFi P5BTX/L,Number Nine S3 ViRGE 2MB,SoundBlasterCT2260,1.2Gb Fujitsu.
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Re: Cyrix Instead - Desktop Build

Postby BSA Starfire » 2015-11-27 @ 12:33

Just reading the text file and this jogged my memory, pretty sure I have this switch on. Might well help you too.

*REDUCED PERFORMANCE AND THE -x PARAMETER*
------------------------------------------
If running 6x86opt gives a decrease in performance you should give the
-x command line parameter to 6x86opt when executing it. When defined,
bit 1 of DBR0 will be set, and a performance increase should result.

Some systems need to have this parameter defined. Also other systems can
can benefit from setting this bit. But as the documentation for this bit
like so many others is not available to me, I do not (yet) know exactly
what it does. Therefore it is not included in the default optimization
process.

Feedback of experiences with this is very welcome!
386SX 33MHz,4MB Ram,ALi M1217 motherboard,OAK OTI077 1MB. Seagate ST1144A.
386DX 25MHz,IIT 387,8MB RAM,Opti,32K cache,WDC90C30 512K.Conner CF170A.
IDT Winchip C6 200MHz,DFi P5BTX/L,Number Nine S3 ViRGE 2MB,SoundBlasterCT2260,1.2Gb Fujitsu.
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Re: Cyrix Instead - Desktop Build

Postby Anonymous Coward » 2015-11-27 @ 12:57

Even though the original Cyrix 6x86 (non L version) kind of sucks I still admire it, being one of the few times that another company was almost able to give intel some real competition. The original 6x86 was also the only time in Cyrix's history that they came close to offering a competitive CPU. Plus, that blazing 6x86 logo just kicks ass.

The 166+ was supposed to be my 486 replacement, but by the time I actually had enough money to build my system the 6x86 was more or less finished (and I got a K6-200 instead). Strangely, I still went with an SiS 5571 based motherboard, which would have been much better suited for the 6x86.
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Re: Cyrix Instead - Desktop Build

Postby feipoa » 2015-11-27 @ 18:48

I have never seen a Turbo frequency feature like that on a S7 board. That is pretty nifty.

I spent much time with these Cyrix optimisation programs for 5x86, 6x86, MII, and GXm. For the 6x86, I think you should try DTE_EN, NOLOCK, WT_ALLOC, FAR_COF, fast framebuffer, and data forwarding options. If I recall correctly, NoLock had the largest impact.
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Re: Cyrix Instead - Desktop Build

Postby BSA Starfire » 2015-11-27 @ 20:10

That is intersting, what program and settings would I need for Cyrix Media GX(Compaq presario 2232), it sure could do with a boost if one is available.
Best,
Chris
386SX 33MHz,4MB Ram,ALi M1217 motherboard,OAK OTI077 1MB. Seagate ST1144A.
386DX 25MHz,IIT 387,8MB RAM,Opti,32K cache,WDC90C30 512K.Conner CF170A.
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Re: Cyrix Instead - Desktop Build

Postby feipoa » 2015-11-27 @ 21:11

The MediaGX requires quite the convoluted path to enable the enhancements, a combination of 5x86 programs and 6x86 programs which fix and reverse the negative effects of each other's default parameters. I will need to boot up my GXm system later today to let you know exactly which combination I ended up with. I can do the same for my MII-433 system, which is a little different than the original 6x86 systems.

The problem with the 5x86/6x86 enablers is that they have a check to see if the CPU in use is supported. So nearly all programs don't let me use them. It is only the crappiest, bug-filled programs I could use. I ended up having to use two programs in series to correct some of their incorrect default settings. The only downside is that you end up with a pink font in DOS. You can get the white font back by running a DOS program and exiting, however it would be nice if someone has a simple autoexec program to put the font back to white.

Which CPU do you have in your MediaGX system? Is it MediaGX or GXm, the "m" being MMX-capable, if I recall correctly.
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Re: Cyrix Instead - Desktop Build

Postby BSA Starfire » 2015-11-27 @ 21:47

I'm pretty sure it's a plain GX, but as most diag progs don't seem to recognise the CPU correctly I'm less than certain. Removing the CPU heatsink involves stripping the entire system apart and I'm kinda loath to do that. Here is my original thread when I bought the machine.
viewtopic.php?f=25&t=39809
You actually provided me the drivers(via PM) to get up and running once I had the correct size HD(thanks again!).
386SX 33MHz,4MB Ram,ALi M1217 motherboard,OAK OTI077 1MB. Seagate ST1144A.
386DX 25MHz,IIT 387,8MB RAM,Opti,32K cache,WDC90C30 512K.Conner CF170A.
IDT Winchip C6 200MHz,DFi P5BTX/L,Number Nine S3 ViRGE 2MB,SoundBlasterCT2260,1.2Gb Fujitsu.
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Re: Cyrix Instead - Desktop Build

Postby foey » 2015-11-27 @ 22:03

BSA Starfire wrote:Just reading the text file and this jogged my memory, pretty sure I have this switch on. Might well help you too.

*REDUCED PERFORMANCE AND THE -x PARAMETER*
------------------------------------------
If running 6x86opt gives a decrease in performance you should give the
-x command line parameter to 6x86opt when executing it. When defined,
bit 1 of DBR0 will be set, and a performance increase should result.

Some systems need to have this parameter defined. Also other systems can
can benefit from setting this bit. But as the documentation for this bit
like so many others is not available to me, I do not (yet) know exactly
what it does. Therefore it is not included in the default optimization
process.

Feedback of experiences with this is very welcome!


Thanks, I've just been having a play for some time on the various switches. I've been benchmarking via Speedsys which gives me some kind of indication but Speedsys seems to vary on each boot - obviously there is a margin each time.

Basically I've been playing with the switches and currently using this...

6x86opt.exe -x -F -A -v


(The V is verbose mode so I can see what is being applied) But I'm not sure its providing me any benefit! The above switches do not appear to be slowing the machine down now - just the results show no jump/consistency in performance.

My Speedsys result is :- 91.54 which after a number of runs I'm getting more of, previously I was getting 91.45-48 without the optimization program.
Cyrix Instead Build, 6x86 166+ | 32mb SD | 4mb S3 Virge DX | Creative AWE64 | Win95
ATC-S PIII Tualatin Win9x Build :- http://www.vogons.org/viewtopic.php?f=25&t=40248
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