VOGONS


486 CPU upgrade

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First post, by LewisRaz

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Hello all.

I have a 486 system I enjoy using but would really like it to upgrade it to the best it can be (before costs become silly)
although my first pc was a 486 I am still fairly unfamiliar with the differing socket types and requirements etc.
I blindly got a 486 dx4 100 for it without even thinking about sockets or voltages. I have since checked and the curent sx50 is a 5v chip and the dx4 a 3v. There are no voltage jumpers on the board so I wont be able to use it.

What cpu would I be able to upgrade to on this system? The board has settings for up to a dx2 66 but the socket says it can accept overdrive chips. Something I have never seen in person before.

The usage of this machine is DOS and early windows games. Windows 95 is installed and as expected it isnt exactly snappy.

I have since found JP6 which the case just labels "Default pins 1-2". It does not describe what the jumper is used for. Could potentially be a voltage switch?! The PC is a trigem 486/33mm and hard to locate any information about other than what is printed on the case.

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Reply 1 of 32, by Tiido

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Take a photo of the entire board, if no voltage regulator is visible anywhere the board is likely 5V only.

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Reply 2 of 32, by dionb

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Assuming 5V only, the fastest easily/cheaply available CPU is 486DX2-66.

As for exotic stuff...
- Intel's DX4 overdrive is basically an i486DX4-100 with built-in 5V-3.3V converter. It would let you do 100MHz.
- Evergreen, Kingston and various other vendors made similar upgrade modules with DX4-100 and DX5/5x86-133 CPUs
- With a generic voltage converting interposers you can stick a 3.3V or 3.45V CPU on a 5V board. That would let you use an Am5x86-133.

Cyrix CPUs need more specific settings, if not present on the board they probably won't work. Despite the socket loudly proclaiming Overdrive compatibility, it can't handle the physically bigger Pentium Overdrive (PODP-83) .

Reply 3 of 32, by LewisRaz

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Tiido wrote on 2020-03-06, 23:59:

Take a photo of the entire board, if no voltage regulator is visible anywhere the board is likely 5V only.

Here is the board, there is some hidden under the drives but that is just where the cache sockets are.

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Reply 4 of 32, by Tiido

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It doesn't seem this board has a voltage regulator (usually a 3 legged part attached to a heatsink) so 3V CPUs aren't supported. Dionb has presented options to explore.

T-04YBSC, a new YMF71x based sound card & Official VOGONS thread about it
Newly made 4MB 60ns 30pin SIMMs ~
mida sa loed ? nagunii aru ei saa 😜

Reply 5 of 32, by Anonymous Coward

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[edit by Dominus: removed ebay link]

So now posting eBay links is not allowed? That's retarded.

Last edited by Anonymous Coward on 2020-03-09, 00:22. Edited 2 times in total.

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Reply 6 of 32, by derSammler

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LewisRaz wrote on 2020-03-06, 23:20:

but the socket says it can accept overdrive chips. Something I have never seen in person before.

800px-KL_Intel_Overdrive_DX40DPR100.jpg

That's a 5V DX4-100 Overdrive CPU. They shouldn't be that hard to find on ebay and the like.

Reply 7 of 32, by LewisRaz

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derSammler wrote on 2020-03-07, 09:17:
https://upload.wikimedia.org/wikipedia/commons/thumb/3/35/KL_Intel_Overdrive_DX40DPR100.jpg/800px-KL_Intel_Overdrive_DX40DPR100. […]
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LewisRaz wrote on 2020-03-06, 23:20:

but the socket says it can accept overdrive chips. Something I have never seen in person before.

800px-KL_Intel_Overdrive_DX40DPR100.jpg

That's a 5V DX4-100 Overdrive CPU. They shouldn't be that hard to find on ebay and the like.

There are 2 on eBay UK right now. They are 169 pin and my Cpu is 168. Are they compatible?

Thanks

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Reply 10 of 32, by derSammler

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Really? The two I see there are both the ones you need. If in doubt, check cpu-world.com:

http://www.cpu-world.com/sspec/SU/SU004.html
http://www.cpu-world.com/sspec/SZ/SZ959.html

Both are PGA168.

Reply 13 of 32, by mpe

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derSammler wrote on 2020-03-07, 15:01:

Well, the original DX2 and DX4 CPUs were Overdrive only. The non-Overdrive versions were released later. So this makes sense.

Where is that information coming from?

The original DX4 was announced and shipped to OEMs from March 1994. The overdrives (ODP and ODPR) in July 1994 (first informally mentioned by Paul Otellini at PC Expo, not shipped before 3rd quater of 1994). The write-back version in Oct 1994.

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Reply 14 of 32, by derSammler

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Have to check, but I know for sure I read many sources stating that. Note that I'm talking about retail CPUs only. The non-Overdrive was probably available to OEMs earlier. I'll see if I still have the link to the sources.

Reply 16 of 32, by mpe

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Not sure if the DX4 was ever shipped to non-OEMs (apart from the Overdrive). Estimating that vast majority of CPUs back then was sold through OEM channels. Nobody was really buying CPUs in a super market back then apart from these overdrive boxes which was a niche product.

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Reply 17 of 32, by derSammler

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Well, I bought a Cyrix DX2-80 CPU in 1994 or 1995 (not sure which year was it) in a computer store. That was kind of normal. The Overdrive was for upgrading older boards, I if only that went retail, Intel would have made a very bad decision.

Reply 18 of 32, by LewisRaz

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After thinking about this system I decided to take a look at the cache area and it was unpopulated so I thought I would add some chips from a dead socket 7 system.
One thing I am unsure of is the TAG chips. These are not present on the socket 7 system. Underneath the socket it is asking for 16K x 4 and it is a dip22 socket. a quick search online locates these for sale in germany: "CY7C164-15PC"
My question is would those be suitable and how many would I need? I do have 4 more matching cache chips to go with the ones I have already added if I wanted to.
I am mostly bewildered by this add-in cache business but am trying to learn what I can from past threads on this forum!
I do plan to add a dx4 overdrive when/if I find one for a better price than currently available.

Thanks

Lewis

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Reply 19 of 32, by CoffeeOne

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LewisRaz wrote on 2020-03-08, 22:22:
After thinking about this system I decided to take a look at the cache area and it was unpopulated so I thought I would add some […]
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After thinking about this system I decided to take a look at the cache area and it was unpopulated so I thought I would add some chips from a dead socket 7 system.
One thing I am unsure of is the TAG chips. These are not present on the socket 7 system. Underneath the socket it is asking for 16K x 4 and it is a dip22 socket. a quick search online locates these for sale in germany: "CY7C164-15PC"
My question is would those be suitable and how many would I need? I do have 4 more matching cache chips to go with the ones I have already added if I wanted to.
I am mostly bewildered by this add-in cache business but am trying to learn what I can from past threads on this forum!
I do plan to add a dx4 overdrive when/if I find one for a better price than currently available.

Thanks

Lewis

Now I must comment on that 😁
Has that board 4 Tag RAM chips?
I never have seen such a board. Or maybe just 2 tag rams, but what are the other 2 sockets then?
Can you make a photograph of the cache area where we can see the writing?

Another remark:
You seem to have 4 pieces of 32x8 cache srams, so it would be 128kB L2 cache
But when you have NO tag/alter ram chips, you have in fact zero L2 cache.
You don't have that board for a long time, do you? Somebody has removed the tag rams 😁