VOGONS


First post, by TELEPACMAN

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Recently someone was asking about upgrading a 486 33MHz with a DX2 66MHz and I was quite happy with the answer, because it seems it 's quite easy, as long as the board has the 2x multiplier you just drop the DX2 in and that is it. I can't find that post anymore... anyway my question is the reverse.

I have a dos machine that I like very much and it has a 486 DX2 66MHz. I would like to downgrade it to a 33MHz 486DX, however this is a late 486 system and only has a jumper to select between DX2 and DX4. One can also select 25 or 33 BUS. Although the DX2 I have is WBack I have the mboard set to Wtrough and it works fine.

Here is the only information on the 125 page manual about the jumpers for the cpu. It is a Hewllet Packard Vectra VE 4/66:

donni_zps1jrwy3yw.png

Reply 1 of 18, by dirkmirk

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It probably doesn't matter with that CPU as the internal clock is not doubled or tripled it will run at 33mhz regardless, A DX2 is internally clocked doubled and the DX4 is clock tripled, just have it set for DX2 if that doesn't work try DX4 otherwise its probably the write back/write through jumper should be set to write through I believe.

Reply 2 of 18, by TELEPACMAN

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Thanks, I will give it a try. I better get a heatsink, apply some thermal and put a fan on the heatsink in case it manages to boot at 66Mhz?

Reply 3 of 18, by Anonymous Coward

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If your board only supports 3.3V CPUs (which is rare, but possible), then a 5V DX-33 will not work.

There is no chance your DX-33 will accidentally run at 66MHz in your system which is set for a 33MHz bus. I wouldn't even worry.

"Will the highways on the internets become more few?" -Gee Dubya
V'Ger XT|Upgraded AT|Ultimate 386|Super VL/EISA 486|SMP VL/EISA Pentium

Reply 4 of 18, by carlostex

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Just try it. The CPU will never be overclocked as it won't respond any multiplier setting. It's just a matter if the Board supports 5V CPU's and the BIOS supports it as well. It's likely that even if the Board works with a DX-33 the BIOS could potentially misidentify it.

It's an OEM Machine, so the BIOS could have very exclusive CPU support.

Reply 5 of 18, by TELEPACMAN

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Ok, it boots and the bios identifies it as a 33MHz and it seems to work fine while at the prompt, so far I tried some Doom, but it freezes after a while...

Reply 6 of 18, by carlostex

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Did you set the cache as write thru?

Reply 7 of 18, by TELEPACMAN

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well, according to the manual JP8 is set to WT, but I can't find any JP10 and I'm just confused.

Reply 8 of 18, by dirkmirk

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Did you change the Voltage jumper on the motherboard? chances are it wil be 3.3/5V doubt it will have 4 as well, Like the others have said it may not support 5V if its one of the later oem systems.

If it doesn't support 5V CPUS it might have a silver square on the motherboard that's blank with the voltage settings silk screened nearby.

Reply 9 of 18, by TELEPACMAN

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carlostex wrote:

Did you set the cache as write thru?

Well I'm still trying to figure out the above instructions! What the heck am I supposed to do?! What do these cryptic Cache Mode Selections even mean???!!! 😵

This might help you to help me:

At the moment it is Write Back confirmed and the jumpers are: 2-3 for the JP8 and 1-2 for the JP10, should I simple reverse this? Because that's not what the instructions are saying, wtf?

Reply 10 of 18, by RacoonRider

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Perhaps you could try to run your DX2-66 as DX2-50? That would possibly give you the slowdown you need while keeping your system stable.

Reply 11 of 18, by TELEPACMAN

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I was considering installing the DX2 50MHz I also have, perhaps if I discover a game wich need more than 33MHz, thanks for the tip. By the way your new avatar is awesome!
I think there is an error in the manual and one can not guide from it, so here is waht I did: I went ahead and changed the JP8 to 1-2, and the JP10 to 2-3 (exactly the opposite of the default) , so far played a bunch of hours on Doom and also some Need for Speed. Completly stable with the 486 being correctly recognized in the BIOS.
You can play Doom and NFSpeed just fine but the DX2 makes a difference. However I still prefer the 33Mhz CPU.
I really like this DOS PC and want to do a post just showing off and telling why I like it so much. Bye.

Reply 12 of 18, by RacoonRider

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TELEPACMAN wrote:
I was considering installing the DX2 50MHz I also have, perhaps if I discover a game wich need more than 33MHz, thanks for the t […]
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I was considering installing the DX2 50MHz I also have, perhaps if I discover a game wich need more than 33MHz, thanks for the tip. By the way your new avatar is awesome!
I think there is an error in the manual and one can not guide from it, so here is waht I did: I went ahead and changed the JP8 to 1-2, and the JP10 to 2-3 (exactly the opposite of the default) , so far played a bunch of hours on Doom and also some Need for Speed. Completly stable with the 486 being correctly recognized in the BIOS.
You can play Doom and NFSpeed just fine but the DX2 makes a difference. However I still prefer the 33Mhz CPU.
I really like this DOS PC and want to do a post just showing off and telling why I like it so much. Bye.

We're looking forward for this post and lots of pics!

P.S. Thanks! Here's the full picture btw 😀
001.png

Reply 13 of 18, by TELEPACMAN

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Magnific! Is this 3D?

Here you have, with lots of pics! 😀 Showing-off my 486 :-)

Reply 14 of 18, by RacoonRider

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TELEPACMAN wrote:

Magnific! Is this 3D?

No, it's quite real!

There are more pictures/details in the article over here: http://www.phantom.sannata.ru/konkurs/2015/kt1506.shtml
It's in Russian, I'm looking forward to writing the same thing in English to share with Vogons 😀

Reply 15 of 18, by Stiletto

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RacoonRider wrote:
No, it's quite real! […]
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TELEPACMAN wrote:

Magnific! Is this 3D?

No, it's quite real!

There are more pictures/details in the article over here: http://www.phantom.sannata.ru/konkurs/2015/kt1506.shtml
It's in Russian, I'm looking forward to writing the same thing in English to share with Vogons 😀

That Front bay switch panel tho...

... that is not real... 😁

"I see a little silhouette-o of a man, Scaramouche, Scaramouche, will you
do the Fandango!" - Queen

Stiletto

Reply 16 of 18, by ODwilly

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Actually there is a thread where he fooled some people into believing that it was a 90's part that he found complete with a Boeing themed instruction booklet 😁 that was a great prank!

Main pc: Asus ROG 17. R9 5900HX, RTX 3070m, 16gb ddr4 3200, 1tb NVME.
Retro PC: Soyo P4S Dragon, 3gb ddr 266, 120gb Maxtor, Geforce Fx 5950 Ultra, SB Live! 5.1

Reply 17 of 18, by Stiletto

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ODwilly wrote:

Actually there is a thread where he fooled some people into believing that it was a 90's part that he found complete with a Boeing themed instruction booklet 😁 that was a great prank!

I remember and I was harassing him about it above 🤣
BusMaster2000: Ever seen such a device?

"I see a little silhouette-o of a man, Scaramouche, Scaramouche, will you
do the Fandango!" - Queen

Stiletto

Reply 18 of 18, by TELEPACMAN

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RacoonRider wrote:
No, it's quite real! […]
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TELEPACMAN wrote:

Magnific! Is this 3D?

No, it's quite real!

There are more pictures/details in the article over here: http://www.phantom.sannata.ru/konkurs/2015/kt1506.shtml
It's in Russian, I'm looking forward to writing the same thing in English to share with Vogons 😀

Google translator worked well enough. I'm in love with your PC, fake parts and all! 🤣