PB450, Cache, and Melting

A) what you're calling 10-pin is DIP-20 package. I'm not aware of SRAM of that size, but if it is, I suspect that it is incompatible.

C) Intel 4004? That is not any sort of PC processor. That is a very early intel design pre-dating the IBM PC by several years. The original PC had an 8088 at 4.77MHz.

fitzpatr wrote:

PB450, Cache, and Melting

A) what you're calling 10-pin is DIP-20 package. I'm not aware of SRAM of that size, but if it is, I suspect that it is incompatible.

C) Intel 4004? That is not any sort of PC processor. That is a very early intel design pre-dating the IBM PC by several years. The original PC had an 8088 at 4.77MHz.

The last part of "C," was more of a dumb joke than anything else. I was basically asking if it would end up being slower than sin.

As for A, I hope that's not the case. There are other removable chips with 8 pins on each side, but I'm not sure if they're cache at all.

If your memory chips really have 20 pins, chances are it wa dram, not sram. You should really avoid popping chips smaller than 28 pin into you cache sockets unless the manual says it's okay. Go on eBay and get yourself some proper 28 pin cache chips.

Anonymous Coward wrote:

If your memory chips really have 20 pins, chances are it wa dram, not sram. You should really avoid popping chips smaller than 28 pin into you cache sockets unless the manual says it's okay. Go on eBay and get yourself some proper 28 pin cache chips.

I've been looking around, and it does seem that these chips are in fact SRAM of some kind. They are Sanyo LC324256P-80 chips, and I've seen "SRAM," associated with them a few times in various places.

I've also tried looking for manuals, although they don't seem to give any useful information regarding the L2 cache.

[EDIT]

It is dynamic RAM. The shorter chips I also mentioned are dynamic RAM, Intel P21256-08 chips. So now my question is why?

Why are there multiple kinds of socketed DRAM chips on this board and no SRAM in sight? Isn't DRAM just ordinary RAM? The sticks of RAM on the motherboard aren't enough? I don't understand any of this. It's also incredibly frustrating because I really don't have any money left to spend on this machine. 28-pin cache like that is always described as "386/486" cache when I look it up, yet this specific 386 motherboard just happens to use some sort of different, arguably infuriating design.

So why the extra socketed DRAM chips when the friggin thing has normal RAM slots?

A picture is worth a thousand words

Take one of the board and post back

No way. If they're 80ns, they're definitely DRAM. The whole point of using SRAM is that it's faster than DRAM. The slowest SRAM I've ever seen used in PCs was 35ns.

Anonymous Coward wrote:

No way. If they're 80ns, they're definitely DRAM. The whole point of using SRAM is that it's faster than DRAM. The slowest SRAM I've ever seen used in PCs was 35ns.

I just bought 128KB (4 32k chips) of 28-pin 20ns SRAM from eBay. I was very lucky to be able to do that.

on ebay and from china? they are most likely not originals but the counterfeit Chinese ones still do the job ok, however there is a higher failure rate so if u get a batch there might be 1 or 2 faulty keep that in mind when you install and run them.

simplest test is keep checking temperature with your finger to see none are shorting

treeman wrote:

on ebay and from china? they are most likely not originals but the counterfeit Chinese ones still do the job ok, however there is a higher failure rate so if u get a batch there might be 1 or 2 faulty keep that in mind when you install and run them.

simplest test is keep checking temperature with your finger to see none are shorting

Nope, not cheap Chinese chips. I even looked up the part number and got datasheets for them. https://www.datasheets360.com/part/detail/km6 … 00167914331251/

They're from the US (Massachusetts), and so shipping will be much faster than if I bought them from overseas (I'll get them in roughly 3 days). Here's the eBay link:

https://www.ebay.com/itm/KM68257CP-20-SAMSUNG … ec4da%7Ciid%3A1

I specifically make sure that I avoid things like that. These are Samsung memory chips, and I did pay a premium for them (compared to the cheap ones), but the only others I found were unlabeled and sketchy.

The more I learn about this, the more I want to rip my hair out. I installed all 4 cache chips correctly, set all the jumpers and even the BIOS settings correctly, and...

Nothing.

Guess what, folks? You now need a "Cache TAG module"! Something that I have never heard of once, nor have I heard anybody else discuss it before. Not LGR on his 486 build, not anybody else on any 486 builds at all, either.

Here's what the diagram on the inside of the case says:

And yes, I avoided the top two rows of pins. The cache doesn't get hot or anything, it just does nothing.

If you can more of that photo would actually help us help you. all the information is probably on it.

flakes wrote:

If you can more of that photo would actually help us help you. all the information is probably on it.

Sorry it took me a bit, I've had work and it's taken me a little bit to get up to actually getting a picture of it. Here's the entire diagram:

It's sideways, but it should be high-resolution enough to where you can see everything including the small text.

Hi
You will definitely need Tag chip in Location 5. The jumpers may be set fine (0 or 128k) if you are only using 128K. If you were buying more to get a Tag ram, you may as well populate the 2nd row and set the jumpers according to the table for J16 and J17.

flakes wrote:

Hi
You will definitely need Tag chip in Location 5. The jumpers may be set fine (0 or 128k) if you are only using 128K. If you were buying more to get a Tag ram, you may as well populate the 2nd row and set the jumpers according to the table for J16 and J17.

If you're suggesting that I fill the rest of the slots with another 128k, I don't think that I can do that right now. I was lucky enough to be able to get the US$16 set in the first place, and I ended up going with that because I had no idea that TAG RAM even existed. What I'm now confused about is the TAG RAM- is it a different kind of chip, or is it the same as the other chips? Are they hopefully easy to find?

If I can get a RAM chip that will work as a TAG chip for a somewhat cheap price, I'll try and go for it. I just don't think I could afford another 128k at the moment.

it's the same chip, usually 9 identical chips work fine. And it's completely normal: just look at any picture of a 486 board with cache and you'll see 9 chips in most cases.

meljor wrote:

it's the same chip, usually 9 identical chips work fine. And it's completely normal: just look at any picture of a 486 board with cache and you'll see 9 chips in most cases.

Oh. If I can find an identical chip, I'll use it. Though the chips I'm using are 20ns, and the diagram on the inside of the case says it uses a 15ns chip for the TAG module. Is that something I should worry about, or just one of those things where the manufacturer says you need a specific kind of item when other things will work just fine?

I should also mention here that I'm very thankful for the help. I always felt like I could work on a PC of this age with no problem, but there are learning curves I figured out that I have to get past. I've said it before that I now am very good with the Slot 1 platform, at least, boards using the 440BX and similar chipsets, but this is quite a large jump from Slot 1, skipping Super Socket 7, Socket 7, and Socket 5, all in one go.