Look for 128K X 8 BIT chips. You can buy counterfeit IS61C1024-15N on eBay or elsewhere. You'll need 8 + 1 for tag (that one can be 64Kx8 chip). Order more than you need as those fakes are often faulty.

I don't see any power regulator on the board so the POD83 is likely the fastest that can run on this board. Or use a separate 5V->3.3V interposer if you have one. Then you can use 5x86

Don't know exactly what chips you'd need, should be any "regular" ones. but I'd take a look at AliExpress. I got some 256x1 chips there for my 286 and they work just fine 😀 so I expect cache chips to be ok too.

About the CPU:
Have you benchmarked this one side by side with your other 486 with the same cpu?
I'd play around with the CPUs and put the fastest CPU on the fastest motherboard.
Do you have the voltage regulator board? That would make things easier for the 5x86 or any dx4. Otherwise the overdrive would be possible to pair.If you don't want the pod on this board, you could look into a dx2-80. These I find always intriguing because of the higher bus speed.
A DX2 100 (50x2 with a supported dx4) setup would also be cool, but the onboard controllers may disagree. And would require the voltage regulator.
For an odd config on 5v, you could try a DX at 40 or 50 MHz. That is of you don't mind not getting the max out of it.

Those 128kx8 cache chips won't fit this board unless you do a modification. The chips on eBay are 300mil, and it looks like your board needs something wider for the high density cache chips.

You are right actually (just zoomed in on sockets). Narrow DIP28 32kx8 chips would only produce 256kB if I am correct. For more, it looks like wide package SRAMs are needed. Don't have any model numbers at hand.

The wide ones are pretty rare from what I've seen. If you're lucky you might be able to pluck some off an old DEC Alpha motherboard, but getting faster than 20ns might be hard.

It would probably be easier to make adapters.

Can you explain why the narrow chips would be limited to 256kb?
I'm assuming its some kind of addressing limit and finding 256x1 like waterbeesje mentioned wouldn't help?
(not that I can, best I find so far is is 256K 32Kx8)

Few years away from having the tools/space/time to create my own adapters sadly.

Because your narrow sockets can only take DIP28 chips which have a maximum of 15 address pins. So the biggest chip you can use is 32kx8. And that produces 256kB when you use 8 of them.

There are narrow DIP32 chips (64kx8 or 128kx8) but you don't have sockets for these...

That photo looks like an IBM 486dx4 motherboard for a desktop 330.

I would start with the motherboard cache first. See how much can work. Then select a CPU.
66mhz thru 100mhz does not make much of a performance difference when playing DOS games.
A pentium overdrive 83mhz would make the most performance improvement from posts I have read.
5x86-133 is okay but not compared to the
Pentium overdrive.

This looks like the same layout as my IBM Valuepoint (which I thought was a proprietary form factor), was this some kind of standard?

There are jumpers for 3.3v operation but looks like you would need to add a voltage regulator.

mpe wrote on 2020-08-04, 13:16:

Because your narrow sockets can only take DIP28 chips which have a maximum of 15 address pins. So the biggest chip you can use is 32kx8. And that produces 256kB when you use 8 of them.

There are narrow DIP32 chips (64kx8 or 128kx8) but you don't have sockets for these...

What about this? looks like a narrow dip 28 to my untrained eye?
https://www.ebay.co.uk/itm/Samsung-256K-20ns- … fcff8%7Ciid%3A1

chublord wrote on 2020-08-04, 15:17:

This looks like the same layout as my IBM Valuepoint (which I thought was a proprietary form factor), was this some kind of standard?

There are jumpers for 3.3v operation but looks like you would need to add a voltage regulator.

Yes that same jumper is why I assumed it could do 3.3v on closer inspection it says 3.3v regulator board on. So looks like the decision is made for me, which is fine. It's got a DX2/50 currently which is an interesting chip but my Dx2/66 is already holding back majority of my games don't have the need for anything slower.

The PC itself is also called a TCS-9510 what's left of it's official page is below. It's using the semi standard LPX or "pizza box" form factor.
https://www.taiwanexcellence.org/en/award/product/18494

chinny22 wrote on 2020-08-04, 16:20:

What about this? looks like a narrow dip 28 to my untrained eye?
https://www.ebay.co.uk/itm/Samsung-256K-20ns- … fcff8%7Ciid%3A1

Yes. DIP28 but only 256kbit = 32kBytes chips. So they'll make 256kB cache when you use 8 of them.

IMHO 256kB L2 is totally fine for a 486...

ahhh ok yeh bit slow but I get ya now.
I agree 256k is fine, but more is always better in my book 😉

With cache in my opinion it is ok as long as your ram can be cached. So with a 486 and 4-8MB you should be ok with only 64kB.

More cache will improve the performance of course but from 128kB to 256kB only gives you 1-2%. More will not give you any more performance, except if you run programs that fit entirely in the cache memory. But those usually don't need the performance of cache memory or a 486 CPU.

Personally I think going to 1MB only is worth it if you need it to cache a crazy amount of ram. Which in turn isn't even usable with a 486 any way.

The because-I-can-factor is another thing of course... I'd go for it if the chips can be found for reasonably good prices 😀

Basic question which would be pin 1?
Left (side facing the raiser slot) or
Right (side facing the edge of the M/B)

I think pin 1 should be close to the edge of the mb (third one if using DIP28) so chips marking will be upside-down (just like the cirrus logic and other chips on the board) given orientation of your picture.

It might be easier to confirm that by finding pin 14 (VSS or ground) or Pin 28 (VDD or +5V) using a multimeter.

awesome thanks, installed and benching as we speak 😀
glad I checked I'd of assumed the other way round!

Out of curiosity what BIOS options do you have for cache/RAM timings, and write-through vs. write-back L2 cache?
I ask because I have a UM491F board where I have the trouble of not being able to go faster than 3-2-2-2, and write-back vs. write-through making no performance difference, and possibly "always dirty" cache.

On a similar note, do you know if this board supports write-back L1 cache? If not, that would be reason not to put one of the last-line 486 CPUs in it since it won't take 100% advantage of them.

I have seen people on this forum with socket adapters before, I might of seen some on ebay.

Anyways I been looking for 128x8 20ns dips for my Alaris cougar and never found any. Sorry for Hijacking the thread.

jakethompson1 wrote on 2020-08-24, 21:04:

Out of curiosity what BIOS options do you have for cache/RAM timings, and write-through vs. write-back L2 cache?
I ask because I have a UM491F board where I have the trouble of not being able to go faster than 3-2-2-2, and write-back vs. write-through making no performance difference, and possibly "always dirty" cache.

On a similar note, do you know if this board supports write-back L1 cache? If not, that would be reason not to put one of the last-line 486 CPUs in it since it won't take 100% advantage of them.

Not many at all. It's running a Phoenix BIOS which was never known for having many options but this looks to be an even earlier version with even lass options then my other 486 also with Phoenix.
I am already thinking of swapping CPU's around once I repair that other 486 but for much less technical reason.
Post shows it as a DX2 100 which is kind of funny as the jumper settings silkscreen on the board say DX4, I guess no one updated the bios code. Bench marking confirms it's running at 83Mhz so it's only cosmetic but I want people to know I'm running a POD damn it 😀

I'll check the memory timings system that I pulled the POD out of once I install its 5x86. That has an award BIOS with proper memory options

Warlord wrote on 2020-08-24, 22:32:

I have seen people on this forum with socket adapters before, I might of seen some on ebay.

Anyways I been looking for 128x8 20ns dips for my Alaris cougar and never found any. Sorry for Hijacking the thread.

No problem hijack away I've gotten everything I need from this thread.
I did come across some solder-less adapters on somewhere like digikey but they were going for more then the chips themselves. This will have to be a project for after the kids get bit older and I get my afternoons back 😀