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First post, by pico1180

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The motherboard is an Asus ISA-486S

I was hoping to get a lesson in how to read cache nomenclature. Or at least find a place that publishes the specs. I don't know how reliable stason is, or who has mucked around with this mother board in its 30 years of existence, but the cache configuration that is present on the board isn't one of the configurable combos shown on stason.org

When I boot the motherboard is says there is 64KB of cache. That does coincide with the setting on the motherboard (not pictured), but the configuration of the cache chips on the motherboard doesn't seem to coincide with... anything.

If I knew how to read the cache chips, or find a database containing the specs of these chips, I could sort this out.

Alternatively, I could just buy all new cache chips, but I don't know how sensitive the board is to specific chips.

A lesson in cache would be very helpful here.

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Reply 1 of 9, by Jolaes76

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You can easily investigate the type of chips with a little googling as the chips are clearly labelled, socketed and almost certainly, not fake 😀
You have a double-banked configuration of 8kb chips, 8 pieces = 64 kb. It is a very early 486 board, using dual TAG chips - but it is important that having both of them in place should NOT break any configuration (probably that is its factory configuration so that one can install any valid combination of chips).

The rule of thumb is that chips cannot be auto-detected so the jumper settings on the motherboard MUST be correct. Again, in some cases, larger capacity TAG chips or dual TAG chips are also allowed for the SAME cache bank configuration, so there is a little elbow room there.

In general, double-banked cache tends to be more common and reliable.

Your motherboard has write-thru cache, meaning that

64 kb cache is enough for 16 MB RAM
128 kb cache is enough for 32 MB RAM
256 kb for 64 MB RAM * this is not possible with using only commonly available SIMMs, memory add-on card must be installed

Later motherboards with write-back cache need twice the cache size for the same amount of RAM (128 kb for 16 MB, 256 kb for 64 MB and so on)

Your motherboard also has a proprietary 32 bit slot for a memory card, which might be unobtainium.

I would say either stick with this cache configuration,
or go up to 128 kb cache / 32 MB RAM and you will have a better Windows 3.1 experience index 😀
Cache speed is also a very important factor, so if you have decent SIMMs then you might want to switch to 15-20 nanosec cache chips and TAG chips with the same or better speed.

Currently you have 25 ns chips and TAG RAM ( "25N" means the speed rating on the cache chips)

"Ita in vita ut in lusu alae pessima iactura arte corrigenda est."

Reply 2 of 9, by pico1180

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Thank you very much for that information. I did try to google it, but I honestly couldn't find anything that I would take to be solid authority. I did find product advertisements though. For example, Amazon says they are 8kx8, and they are abundant on eBay, but the sellers do not advertise their capacity. To cause further confusion, the Sony TAG chips come back as "16x4" but the spec sheet from stason implies they should be 8kx8. So, ya. I couldn't find anything that I believed to be definitive.

Clarification on a few issues:

Would there be an issue if I added 256 without 64MB of RAM? I ask this because it seems as though the 32kx8 chips are abundant and plentiful on eBay.

Can I use any cache chips that are pin compatible and size appropriate? Or are ISSI's the only ones that will work?

Reply 3 of 9, by Jolaes76

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If speed is not important, then you can skip on the TAG question as the current TAG configuration supports 256k cache, too.

If you want faster cache, TAG swap is necessary.
In this case, it is indeed a bit of a gamble because the motherboard MIGHT be picky about the TAG.

When the cache is working OK, regardless its size, it must not cause any stability issue whatever your RAM size/configuration is.
Even a smaller-than-optimal cache configuration will work with a big RAM size, you only will notice the general speed drop under heavy load.
Having a bigger cache size and smaller RAM amount will absolutely do no harm (but no benefit either). So yes, you can safely upgrade to 256k.

The manufacturer is not important, having the same type of chip should do the trick. I would pick the best speed available (15ns, 12ns)

Before buying, think it over whether a general 5-8 percent speed increase is worth the price to you.
This motherboard can only go significantly faster with an overdrive processor.

25ns is the fastest TAG chip from SONY. Ebay ads say that these are compatible: AM99C165 , CY7C166 , HM6289 , HM6789 , HM65789 , IDT6198 , IDT7198
Maybe there is a 25/ 20 / 15 ns equivalent among them.
But as I said, a 33 Mhz 486 processor might not be the best platform to highlight the better cache configuration.

"Ita in vita ut in lusu alae pessima iactura arte corrigenda est."

Reply 4 of 9, by pico1180

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In your experience would these appear to work for the cache, or are they a different thing?

https://www.ebay.com/itm/SRAM-32kx8-Static-RA … 75.c10#viTabs_0

https://www.ebay.com/itm/SRAM-32kx8-Static-RA … 353.m1438.l2649

Reply 5 of 9, by Jolaes76

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No,

I think you did not specify "DIP 28" in your ebay search.
You need the sleek chips 😀
I.e.
https://www.ebay.com/itm/2pcs-UM61256FK-15-UM … GQAAOSwwzhZU03T

"Ita in vita ut in lusu alae pessima iactura arte corrigenda est."

Reply 6 of 9, by pico1180

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Sorry to keep asking mundane questions, but mucking with cache is new to me and I want to understand it the best I can.

I tried to set up, what I believed would be 128k, but it didn't change anything. I thought the IS61C256 were 32x8, but am I mistaken? Could you look over the settings and the chips and tell me what I missed. The cache amount still reports as 64k.

After that, I pulled out all the cache chips and it still reported 64k. I'm at a loss.

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Reply 7 of 9, by Eep386

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Did you make sure the jumper settings for the cache were correct? Also the TAG should match the cache setting.

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Reply 8 of 9, by Jolaes76

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The manual says that U28 TAG must be removed in this configuration, try that. Or perhaps it is U27 (=error in the manual).
Btw, you need to test the cache size in DOS as well, with cachechk or a similar utility.

On a sidenote, the BIOS of certain motherboards with fake-cache always report the same amount like "64 kb WRITE-BACK cache enabled", no matter what you change (jumpers/chips).
These chips do not look fake, of course. IS61C256 chips should work in this array.

"Ita in vita ut in lusu alae pessima iactura arte corrigenda est."