Mau1wurf1977 wrote:

Hehe no worries LOL […]
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Hehe no worries 🤣

Regarding the CPU voltage. Isn't it odd that a board with VLB and PCI doesn't have an option for 3V?

There are a set of jumpers around the voltage regulator. I'm thinking it should be possible to remove the CPU and measure the voltage at whatever pin...

I mean it does support the Pentium overdrive, so surely it would support the DX4? It does have a multi jumper (2x, 2.5 and 3x). But compared to other 486 boards, it does lack a lot of jumpers. E.g. most 486's have an armada of jumpers close to the CPU socket which sets the CPU type and things like that.

Also I have been removing jumpers here and there and everything still works. Quite odd to see all these jumpers with no description. Total mystery...

There were several CPU upgrades made specifically for fitting 3.3v parts into motherboards that supported only 5v parts.

Evergreen and the Kingston Turbochip are 2 of them.
Just fyi 😉

True...

I think I will just get the cache chips and be done with it!

Mau1wurf1977 wrote:

And another curious jumper:
W (with?) 1435
W/O (without?) 1435

Maybe you can disable the PCI bus because 1435 is the name of the VLB->PCI bus bridge device ?

Try upgrading video memory to 2 MB . The Mach32 can do 1024*768 @ 65k colors with 2 MB.

I will try it out!

That's a sweet little system you picked up! I've always liked the cases of the early Acers

I mean it does support the Pentium overdrive, so surely it would support the DX4? It does have a multi jumper (2x, 2.5 and 3x). But compared to other 486 boards, it does lack a lot of jumpers. E.g. most 486's have an armada of jumpers close to the CPU socket which sets the CPU type and things like that.

DX4's were available in both 5V Overdrive and normal 3.3V versions. I was using a 5V DX4 Overdrive in my machine for a while, the 3.3V ones are flat on top like any other ceramic processor while the Overdrive one had voltage regulators and a heatsink about an inch high built in to the top. The Pentium Overdrives just worked off either voltage I believe (they also had voltage regulators built in, plus a heatsink and unlike the DX4, a fan). I've actually got a new-in-box Pentium Overdrive 83MHz at home somewhere; I'll have to check the specs of it 😀

anyway, it really seems to be that your board only supports 5V CPU's; but its not really a big deal as there are ways around that 😀

DonutKing wrote:

anyway, it really seems to be that your board only supports 5V CPU's; but its not really a big deal as there are ways around that 😀

You can clearly see the voltage regulator onboard. It is possible, that the thing supports automatic voltage detection as most of the Asus 486 mb's do (e.g.).

Hmm interesting.

The DX2-66 does have 3V written on the cooler, but I can't get it off to see what's written on the chip.

I'm pretty sure that's actually a version number. I've got a DX2/66 with V4.0 written on top but its definitely a 5V processor. I've also seen some DX4 Overdrives with V1.0 or V1.1 written in that spot. You can tell by the s-spec, yours is SZ878 which is a 5V CPU 😀

Ahhh okido!

How are you getting on with this fun project? It's really good to see that you've got a 486. From the title of your thread, I understand that you want feedback as to what to do with it. I've got a suggestion. I'm in the very early stages of seeing how useful a 486 is, in order to run speed sensitive games from the 386 era. My very early conclusion is that it's more flexible than a 386 itself. In my tests, I used an Intel 486 DX-33 chip, and as luck would have it, I notice that you have one too, already installed! As a suggestion, why not try the following:

(A) Research the identities of 386 era games that are speed sensitive.

(B) Benchmark your 486, and draw up a kind of "speed table" by using the same CPU, but use different bus speeds, toggle the cache(s), toggle the turbo button, and alter the BIOS timings. You could also use a PCI and an ISA VGA card, but I would stick to a PCI card to begin with.

(C) Run as many games as you can get hold of from list (A) on DOSBox, to determine their optimum speed.

(D) Then rerun each game on your real 486, and alter the 486's configuration (B), so that the speed of each game equals that of the optimum speed determined in (C).

(D) Then "slot in" each game title in to the table (B)

(E) Get on with it! 😉 😉

(A) Research the identities of 386 era games that are speed sensitive.

Piece of cake! Wing Commander and Test Drive III are good examples!

(B) Benchmark your 486, and draw up a kind of "speed table" by using the same CPU, but use different bus speeds, toggle the cache(s), toggle the turbo button, and alter the BIOS timings. You could also use a PCI and an ISA VGA card, but I would stick to a PCI card to begin with.

Well as you know it's an ACER. The BIOS has zero options regarding performance. Also no Turbo button and currently no L2 cache installed.

Only option I have is disable L1 cache through software, which gets me a 3dbench score of 6.9.

At full speed I get a score of 25.

(C), (D), (E)

At this point it's an easy conclusion. Without L1 cache it's too slow for 386 games and with L1 cache too fast. Once I have L2 cache, disabling L1 cache should give me a decent 386 machine equivalent.

Get on with it! 😉 😉

I was hoping for more input regarding jumper settings, but most has been deciphered already, but some bits will likely remain a mystery (e.g. how to set 25MHz fsb) or getting documentation for the mainboard.

The PC has been assembled in Australia, so maybe that's why there is so little documentation. There is a chance of finding documentation is asia, but I have no idea how to approach this.

Australia has very strong ties to Asia, so it's likely this is a Asia Pacific region only model.

All in all I'm happy, the PC works, my SB 2.0 work, so does my PAS16 and I can test ISA, VLB and PCI cards if I want to 😜

I f I need more grunt, I have a excellent SS7 PC on the same bench.

PS: these 486 chips get quite hot. I take it this is normal? The 486DX-33 doesn't have a cooler and I believe that's fine right?

I do have some chips with coolers on them, but yea no idea what chips they are 🤣

Yeah they do get pretty hot but its normal.
When I had a 486SX back in the 90's it used to crash in the aussie summer heat. Not all the time though, and only after a few hours prolonged use.
The Overdrives have a built in heatsink which helps a bit.
I installed a case fan at 7V in my DEC to blow a small amount of air over the CPU and this made a dramatic difference to temps, before you could nearly burn your finger on it, with jsut a little bit of airflow it cooled down a lot.

I had another go at trying to track down the manual for your machine. Turns out there's another AcerPower SP that was a socket 478 machine 😒

Yea I think I will leave it at that. Just going to keep an eye out for some cheap cache chips.

The sockets are different sizes which is interesting. Are the larger ones for when you want to upgrade to 512kb?

I think the larger ones are just for different packages of SRAM chips. I've got a couple of motherboards that have sockets to accomodate both sizes, but they supposedly only take 256kb cache, which they have installed in the smaller chips. I don't know if there is any difference apart from the physical size.

I just noticed something. In this photo on the right there seems to be a bank of jumpers, JP15 and JP16, and Ithink I can see a '25M' and maybe a '40M' next to them. Perhaps these jumpers set the FSB as well? I didn't see anywhere that explains their settings (unless I missed it).

I just noticed something. On the right there seems to be a bank of jumpers, JP15 and JP16, and Ithink I can see a '25M' and maybe a '40M' next to them. Perhaps these jumpers set the FSB as well? I didn't see anywhere that explains their settings (unless I missed it).

OMG

You're the man! Australia represent 🤣

25, 33, 40 and 50 MHz! There they are!

Set it to 25 and fired it up. Had a "Computer missconfiguration" message but otherwise all good!

Happy to be of service 😀

After fiddling with this old stuff for a while you develop a keen eye for obscure silkscreen markings on circuit boards 😜

I can see 25M, 33M, 40M and 50M and the last one seems to be undocumented.....😁

Tetrium wrote:

undocumented

Must be warp speed 😜

Tiny update!

Now that I have 25MHz running and everything is stable, just need to pack it all together. I do have a CF reader for the rear slot, but the cabling is a pain, so I will get one of these 5.25" IDE bays:

http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewI … e=STRK:MEWNX:IT

Then can hook up my IDE DVDRW and CF adapter onto the single IDE port and also have a floppy drive.

Also what software should I use for >500MB support? Anything that's free, easy to use and "just works" would be nice 🤣