feipoa wrote:

Pentium running at what internal frequency? 1.5x40 = 60 MHz? I wouldn't mind seeing a first generation Cyrix 6x86 run at 1x40 MHz with accompanying Speedsys screenshot.

That is correct. 40mhz FSB.

From what I can find online the P54SP4 does not support Cyrix and AMD K5 CPU's. My PCI/I-P54TP4 does support it, and it can do 40mhz FSB, so that would be the board to test it with.

Did you try a 1st gen. Cyrix 6x86 on the P54SP4? If so, what happened?

feipoa wrote:

Did you try a 1st gen. Cyrix 6x86 on the P54SP4? If so, what happened?

Don't own one, so can't confirm. I do have a IBM 6X86 2V2P166GE 133MHZ-3.3V waiting for me in the US, but does this count as a first gen Cyrix? Is it only the 80 to 100 that are first gen and can do 1x multiplier?

I do own an AMD K5 first gen and that did not work.

I am not sure all of which 6x86's can do 1x. I only recall trying my 6x86-80 at 1x because I was shooting for 80 Mhz operation on a TX board. I ran it at 1x75 and 1x83. 1x75 ran fine, however one or two benchmarks at 83 MHz required a rerun. This chip got a lot hotter than my 6x86-P150, although they both run at the same voltage. I do not know what Cyrix changed between the 6x86-80 MHz and the 6x86-100 MHz series and the 6x86-P120, aside from their brilliant naming scheme. But from this anecdotal account, it seems they may have done something to reduce heat built-up. From past readings, it seems Cyrix made some incremental changes along the way within their core designs that didn't do a whole lot for performance. If you have an IBM 6x86-P166, could you let me know if it works in your P54SP4? I have a casual interest in getting an original Cyrix 6x86-80 running with a 40 MHz FSB on a socket 5 - the catch being that the board must take L2 DIP only, and hopefully up to 1024KB.

The P54SP4 supports only L2 async DIP cache (no PB) and 1024KB, so that criteria is met. I'll test my IBM 6x86-P166 when I get hold of it. I'll also try and get hold of a older CPU, but they seem to be more rare.

Patiently looking forward to some benchmarks whenever the parts are in.
Like I said, My Cyrix 6x86L PR200+ supports 1.0x reliably. This is the second generation 6x86 split voltage model, 2,8 Volt, socket 7 spec. Based on what is sometimes printed on the CPU, they are also sold as 3,3 Volt only, socket 5 spec. It kinda defeats the whole point of the L-versions. Don't have any to try. Instead I do expect another 6x86L PR200+ to arrive soon, an IBM branded one.
This evening I will expand my earlier post with the speedsys screenshot, as to include some of the benchmarks that vetz used. Currently I cannot properly compare.

I placed my Powerleap PL-K6-III adapter in my Socket 5 ASUS P54TP4. Since it has an undocumented FSB option of 80mhz, I managed these results:

AMD K6-III @ 480mhz:

3DBench2: 343,1
PCPBench: 114,5
DOOM FPS/TICKS: 113,86/656
Quake: 59,9

Quite impressive for a board from Jan/Feb 1995.

I've benched alot more with alot of CPUs in those Socket 5 boards, but I'll make those public very soon (need to make some graphs and stuff)

Is the board stable enough at 80 MHz to install WinXP without crashing?

feipoa wrote:

Is the board stable enough at 80 MHz to install WinXP without crashing?

No idea, but the board has been stable in DOS at that FSB. My AMD K6-III requires some heavy cooling to run at 480mhz since the AMD K6-III+ is not supported by the board (I tried)

feipoa wrote:

Did you try a 1st gen. Cyrix 6x86 on the P54SP4? If so, what happened?

Yes, I tried the 6x86, 6x86MX, AMD K5 and AMD K6-2 and K6-3 (In PowerLeap adapter) to no avail. The board just refuses to boot.

The fastest speed I managed without the Powerleap was with a Pentium MMX, but it required the L2 cache to be turned off (or else it crashed on boot). You are running the MMX at 3.3V by doing this, but I have 10 of them laying around so I don't care. The fastest possible speed you can get out of this motherboard is a Pentium 200 (3x) in a Powerleap adapter.

Since the MMX does not have a 1.5x multiplier it clocked itself to 133mhz:

1							                                   3DBench2  	PCPB	DOOM FPS/TICKS	   QUAKE	TOTAL
2133mhz MMX, PCI NORMAL, L2 OFF	          	            90,2	 	27,2	50,26 (1486)      	24,3	101,76
3133mhz MMX (1,5x & 3,5x), PCI @ 44mhz, L2 OFF	          95,6	    28,1	56,80 (1315)      	24,9	109,80
4With Powerleap adapter:
5166mhz MMX (2,5x & 3x), PCI OC, L2 OFF	                103,5 		30,8	61,22 (1220)      	27	  119,02
6200mhz Pentium (3x), PCI OC, L2 ON	                    117,9  	  37	  66,63 (1121)      	28,3	131,93

Undocumented jumper settings:
Pentium 25mhz 1-2, 1-2, 1-2
Pentium 40mhz 1-2, 1-2, 2-3
Pentium 50mhz 2-3, 2-3, 2-3

Basically the board can run the Pentium CPU from 25mhz up to 200mhz.

So the board has a 40 MHz FSB option but will not work with the only CPU designed around this bus, the Cyrix 6x86? And the Cyrix 6x86 will not run without the PowerLeap adapter either?

feipoa wrote:

So the board has a 40 MHz FSB option but will not work with the only CPU designed around this bus, the Cyrix 6x86? And the Cyrix 6x86 will not run without the PowerLeap adapter either?

Yes to both 😵 Then again, the SiS 501-502-503 chipset were even available with Socket 4, so I have my doubt they ever thought about Cyrix support, but just imagined other types of Pentiums

I only used the Powerleap on the AMD K6's and 6x86MX. The other two were put directly into the socket.

feipoa wrote:

I have a casual interest in getting an original Cyrix 6x86-80 running with a 40 MHz FSB on a socket 5 - the catch being that the board must take L2 DIP only, and hopefully up to 1024KB.

Feipoa, you're in luck. I just got hold of a Cyrix 6x86-80GP for a few dollars:
http://www.cpu-museum.de/?m=Cyrix&f=6x86#cpu0184

So I'll be doing the bench when I get it in the mail 😀

But will your motherboard work with a Cyrix 6x86?

Is that guy selling off his collection? I've been seeing a lot of that recently.

feipoa wrote:

But will your motherboard work with a Cyrix 6x86?

Is that guy selling off his collection? I've been seeing a lot of that recently.

It will work in my Asus P54TP4 (see this thread: ASUS PCI/I-P54TP4 Socket 5 motherboard thread/review ). I also have Asus P55SP4 (SIS 5511) which supports 1MB DIP L2 cache and the Cyrix 6x86 on the way to me (dunno about 40mhz FSB though)

I just linked to that site to show the version I'm getting (there are a PR90 version as well). It has nothing in common with the seller I bought from.