a 386 with 256K cache? It is done and works, mostly (questions inside)

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a 386 with 256K cache? It is done and works, mostly (questions inside)

Postby Jed118 » 2017-4-14 @ 14:33

So, after a few hours of wrestling the 64K tag chip off the board (I ended up carefully dremeling the legs off) and unsoldering a 28 PIN connector off a parts mobo I have (which also took quite a bit of time) and then carefully soldering that to the legs of the old tag chip,and having to route three pins directly to the reverse side of the board via wiring, it works! It did not work immediately, and I suspect I will have to revisit this and solder a new connector onto the board directly to stave off any future BAD CACHE errors and then (6000:1A40) halt errors after booting. I've left the computer on all night doing testing, and powered it on and off several times and all is well for now.

Not the most elegant solution, but it works for now:

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It was pleasant to see this:

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Now for my question : Are there diagnostic test out there designed to test L2 cache memory specifically?

Also, in the interest of science, I have another identical m321 board (with a DX40) with 128K cache which I would like to benchmark against this one (I can revert this one to a DX40 for testing purposes, then re-add it, then add the co-pro, etc) - Which benchmarking software would best reflect that?
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Re: a 386 with 256K cache? It is done and works, mostly (questions inside)

Postby TandySensation » 2017-4-14 @ 16:02

Amazing, great job!

Don't know of any specific tools for L2, sure you know of all the standard ones. Speedsys should show a graph of the cache, cachchk7 will show in txt, WinTune 2.0 looks pretty if you want to use Windows.

Looking forward to seeing the results posted.
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Re: a 386 with 256K cache? It is done and works, mostly (questions inside)

Postby mrau » 2017-4-14 @ 17:06

so whats the main goal here? any performance comparison to show off?
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Re: a 386 with 256K cache? It is done and works, mostly (questions inside)

Postby 386_junkie » 2017-4-14 @ 18:04

I have to hand it to ya... that is a great, wilful and persevering job you did there, I like it!

I love modding 386 era hardware as and when I need, I can relate.

Crafty goodness! :D
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Re: a 386 with 256K cache? It is done and works, mostly (questions inside)

Postby Jed118 » 2017-4-14 @ 19:02

mrau wrote:so whats the main goal here? any performance comparison to show off?


I never had a 386 with that much cache. I will compare it to an identical one that has only 128K, but I will have to wait until July to do that as I have several PSUs (and other parts) waiting in Poland for me which I will bring back, somehow.
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Re: a 386 with 256K cache? It is done and works, mostly (questions inside)

Postby mrau » 2017-4-14 @ 20:01

i see, so you got some plans there, powodzenia :)

i wondered a bit about modding too, i was thinking to what extent those now slow as a fly in tar cpus could be used years later if we improved their supporting hardware and used adequate software;
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Re: a 386 with 256K cache? It is done and works, mostly (questions inside)

Postby Jed118 » 2018-2-03 @ 04:29

Now that it's the middle of winter, and my summer car (and project car) are firmly stuck in storage (due to snow), I decided to revive the 486DLC project.

I started by removing the shit work I did on the tag chip, carefully desoldering each lead and then putting in an IC socket first, THEN putting in a new TAG chip (actually, I bought 10, and just used the spare).

First shot, stable system operation.

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This looks a hell of a lot better, and less messy:

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Also, it works a lot better :D

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Re: a 386 with 256K cache? It is done and works, mostly (questions inside)

Postby DonutKing » 2018-2-03 @ 08:07

Nice work, and I appreciate the effort of replacing components on the board... but I've been running 256KB cache in my 386 for over 7 years now.....

viewtopic.php?f=25&t=27015&p=208850

As I'm only running 8MB of RAM I don't see any performance or benchmark increase at all from 128KB, but its always nice to max out your system.
I also have 1MB of L2 cache in my 486 but again, I don't see any difference from 256KB.

BTW - here is a utility to test and benchmark L1 and L2 cache: ftp://69.43.38.172/mirrors/cd.textfiles ... chchk5.zip
It also includes a utility to enable/disable L2 cache but IIRC it only works on 486 or better.
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Re: a 386 with 256K cache? It is done and works, mostly (questions inside)

Postby kixs » 2018-2-03 @ 09:06

Sure, a few % can't be seen but it can be measured in benchmarks. Doubling the cache size usually gains around 3-5% - depends on the app used.
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Re: a 386 with 256K cache? It is done and works, mostly (questions inside)

Postby Anonymous Coward » 2018-2-03 @ 12:18

That's a nice, clean Cyrix chip you have there.
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Re: a 386 with 256K cache? It is done and works, mostly (questions inside)

Postby Jed118 » 2018-2-03 @ 16:48

Thanks! I have the matching co-pro, 83C87, which the POST summary doesn't see but any and all diags report it and it passes tests.
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Re: a 386 with 256K cache? It is done and works, mostly (questions inside)

Postby derSammler » 2018-2-03 @ 16:56

I don't get it. That's a PC Chips M321, isn't it? Why any soldering, that board supports 256 kb L2 cache without modification..?
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Re: a 386 with 256K cache? It is done and works, mostly (questions inside)

Postby Jed118 » 2018-2-03 @ 17:07

M321 apparently came in many flavours - Here's the original one I removed from the system:

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The one I had to mod to get 256K was an eBay special, with 64K initially. What I liked about this board is that ALL the DIPs (except the TAG) were socketed, meaning I only had to unsolder the TAG chip vs the TAG chip plus 4 cache chips if I were to do that on the original board pictured above.

I suppose I could have just stuck in an extra 4 256K modules here, but the speeds wouldn't match up (I have 15ns) - I doubt that would make a performance difference, but aesthetically it would - I don't even like mixing RAM speed ratings.

Curiously, the board with 64K had a more advanced BIOS revision (autodetect hard disk, RAM timing, etc) so that one was swapped to the other 256K M321 board.
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Re: a 386 with 256K cache? It is done and works, mostly (questions inside)

Postby Jed118 » 2018-5-10 @ 16:28

So, to address possible stability issues, I've added some heatsinks to the CPU (which gets arbitrarily hot) and to the FPU (which remains at room temperature most times).

I've also put in heat sensors into both of them to get a readout. I plan on replacing the LED readout that tells me the speed of the computer with a tiny LED readout that is programmable via arduino. I already have it and it fits in the stock location just fine. I plan on it displaying the speed and +12 +5 rail voltages, then flipping to FPU and CPU temperatures, alternating every 3-4 seconds.

I cut the heatsinks to fit from a larger heatsink I got from ebay.

For now though, I'll run the system with these on and a big ass fan pointed at them with the case cover off to see if it is indeed a thermal event that's locking up my system.

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Some thermal paste and:

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This JUST clears my AWE32

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