Logistics wrote:

While researching some ancient DIP20 cache for a 486 board, I started thinking about adapters, specifically some to convert SOIC and SOJ to DIP, which I had come across on the net. I ended up finding, iirc, an SOIC chip which was pin-compatible with the original DIP. However, rather than being around 100ns, it was more around 40 or 50 nanoseconds.

25ns chokes at maximum 1/25ns=40MHz bus; it was common in 486SX-25 boards.
20ns chokes at 1/20ns=50MHz bus; it was more or less mainstream for most 486, DX-33 to DX4-100.
15ns chokes at 1/15ns=66MHz; it is quite fast and capable of running at 50MHz bus (hello, 5x86 at 3x50!)
10ns is considered ultra fast and there are people here who know how to obtain some.

Where did you see 100ns?

RacoonRider wrote:

25ns chokes at maximum 1/25ns=40MHz bus; it was common in 486SX-25 boards. 20ns chokes at 1/20ns=50MHz bus; it was more or less […]
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Logistics wrote:

While researching some ancient DIP20 cache for a 486 board, I started thinking about adapters, specifically some to convert SOIC and SOJ to DIP, which I had come across on the net. I ended up finding, iirc, an SOIC chip which was pin-compatible with the original DIP. However, rather than being around 100ns, it was more around 40 or 50 nanoseconds.

25ns chokes at maximum 1/25ns=40MHz bus; it was common in 486SX-25 boards.
20ns chokes at 1/20ns=50MHz bus; it was more or less mainstream for most 486, DX-33 to DX4-100.
15ns chokes at 1/15ns=66MHz; it is quite fast and capable of running at 50MHz bus (hello, 5x86 at 3x50!)
10ns is considered ultra fast and there are people here who know how to obtain some.

Where did you see 100ns?

I do believe there is also 12ns cache. I think feipoa has some but if 15ns maxes out at 66mhz, then you shouldn't need anything faster than that.

Thank you for adding that, I totally forgot about 12ns!

I have one in 430FX-based Lucky Star motherboard as Tag RAM, other chips providing 256kb PB. Interesting thing though, cheap Lucky Star board has 12ns Tag, while much better ASUS PI-P55T2P4 has 15ns. I installed P233MMX on ASUS, overclocked FSB to 75 MHz and it worked fine. Adding the 12ns Tag RAM into an empty socket gave a minor performance increase, and made 83 MHz FSB stable. 291MHz on Pentium I is kinda cool, yet I decided to spare the system I love so much and not to torture it anymore.

This is all very interesting. I didn't know there was a correlation between fsb and cache speed.

However, I realize, now that the cache, with much slower speeds, I was thinking of belonged to an ISA video card. Now, I have to wonder about increasing a 16-bit ISA video cards' speed by replacingall the RAM.

I have not seen any improvement in performance or stability on a 486 when using 10 ns or 12 ns over 15 ns cache on a 486. I think I tested this up to a FSB of 66 MHz.