The 486 bioses have never been online. The manuals have been.

Here's a person that seems to have a 486EI board: https://www.ckits.ca/blog/2018-12-19/128MB-in-486.html

The BIOSes were not on the website, but they *may* have been on the FTP server. The website did have a copy of the user manual, which also would have been nice to have.

Thanks for the tip on the guy with the Dolch Pac60. Though I don't think I'm going to be able to contact him because I don't use twatter. I guess he might have a VOGONS account. Does nobody use e-mail anymore?

I dug around for stuff on the Pac60, but I could only come up with the brochure.

Anonymous Coward wrote on 2020-09-04, 00:19:

The BIOSes were not on the website, but they *may* have been on the FTP server. The website did have a copy of the user manual, which also would have been nice to have.

Thanks for the tip on the guy with the Dolch Pac60. Though I don't think I'm going to be able to contact him because I don't use twatter. I guess he might have a VOGONS account. Does nobody use e-mail anymore?

I dug around for stuff on the Pac60, but I could only come up with the brochure.

I mean I do have an e-mail (kits at that domain if you want), just don't have it linked on that site at the moment (haven't updated it for quite a while). Or I'm on here.

Do you want a dump of the BIOS for it? It's specifically a Dolch modified one for the PAC 60, but I imagine it'll work on any 486EI board (It's a 1.5 in the PAC60 IIRC). Just let me dig up the ROM dump I made when I was going about reverse engineering it to try and find why it was limited to 64MB when the motherboard is advertised as supporting 256MB

The motherboard in the PAC 60 which is labelled as a 486EI 1.5 doesn't have 3.3v regulators to the best of my knowledge, or jumpers for it. But if it did support them that'd be something I'd be interested in too. Being able to upgrade it to a 5x86 rather than a 486DX266 would be nice.

EDIT: Here's the BIOS dump I took from mine, it's a 64kB image, so I believe it was from a 27C512 EPROM or similar https://www.ckits.ca/files/dolchpac60_486ei_bios.bin

EDIT EDIT: Attached it here in case I ever re-arrange the files folder on my website. I try not to break links

Yes, please upload the BIOS if you can!

As far as I know, V1.2 of the board and higher should have had DX4 support (maybe it was optional). Does your board at least appear to have solder pads for the regulator?
I think the fact that the BIOS has been customised for Dolch shouldn't be too big of an issue now, since one of the users on this site has figured out a way to permanently unhide all of the missing options.

The am5x86 should work on your board (with VRM upgrade module), except that it won't be detected properly by the BIOS and you won't be able to use writeback cache.
The cx5x86 probably won't POST on your board. There are ways to get it going, but it's kind of messy. Using the 5x86 databook I attempted to modifiy a few pins on my Nice Super EISA and Tyan S1437 (very similar to your board), but it didn't have any effect. These are the boards I want to try your BIOS on btw.

The AMIBIOS on the NiCE and Tyan boards does support 256MB albeit with 16x16MB 30pin SIMMs. The image uploaded is using the 06/06/92 HiFLEX core, so too early for DX4 support.

I doubled checked with a hex editor to see if "DX4" appears, but nope.
It's still nice to have, and I'll test it out on my boards anyway.
Hopefully the BIOS for the v2.0 will show up at some point.

Anonymous Coward wrote on 2021-09-04, 00:26:

As far as I know, V1.2 of the board and higher should have had DX4 support (maybe it was optional). Does your board at least appear to have solder pads for the regulator?
I think the fact that the BIOS has been customised for Dolch shouldn't be too big of an issue now, since one of the users on this site has figured out a way to permanently unhide all of the missing options.

There's no evidence of of any space for a regulator or even provisions for it, I've looked at it before to see about upgrading, but I imagine that it'd need to be done with an inline voltage adapter for the socket.

NJRoadfan wrote on 2021-09-04, 01:20:

The AMIBIOS on the NiCE and Tyan boards does support 256MB albeit with 16x16MB 30pin SIMMs. The image uploaded is using the 06/06/92 HiFLEX core, so too early for DX4 support.

Makes me curious to try some other AMIBIOS's to see if any will be fine in this board variant, I doubt anything is special for the Dolch (maybe something with it's special vga card). Would be nice for it to see more than 64MB of ram. Even if that's an excessive amount. I've never really messed with swapping around BIOSes on boards. Though I do have some 27C512 Winbond EEPROMs that I could try changing it.

Whatever the reason your system can't detect more than 64MB, the BIOS is not the issue. I tested your PAC60 BIOS on my SuperEISA board and it still counted 128MB.

Unfortunately, the PAC60 BIOS didn't solve my Cyrix 5x86 problem. Even though ELHVB and TH99 claim V1.2 of the 486EI supports 3.3V CPUs, I think it must be a mistake:

https://www.elhvb.com/webhq/models/486vlb3/486ei12.html
http://www.uncreativelabs.de/th99/m/A-B/33191.htm

I think V2.0 is what I need. It's kind of hard to believe it hasn't popped up by now. The 486EI was a pretty popular board.

Anonymous Coward wrote on 2021-09-04, 08:45:

Whatever the reason your system can't detect more than 64MB, the BIOS is not the issue. I tested your PAC60 BIOS on my SuperEISA board and it still counted 128MB.

Interesting, the 486 EI claims to support 256BMB in the configuration I was going for with 64MB simms, and the modules themselves are fine. And it notices incorrect configurations such as putting the second module in the wrong bank. I was figuring it was something broken with the specific bios revision. I still might try a different bios in case it doesn't like the particular dram controller on here or such. Will have to look into that more then, for now 64MB is plenty though, especially without more cache.

Anonymous Coward wrote on 2021-09-04, 08:45:

Unfortunately, the PAC60 BIOS didn't solve my Cyrix 5x86 problem. Even though ELHVB and TH99 claim V1.2 of the 486EI supports 3.3V CPUs, I think it must be a mistake:

Yeah, though to be fair I'm not actually sure where the V1.51 board in the Dolch actually fits in. It's possible that it's older than the V1.2 and just the numbering scheme changed. I haven't seen any references to this board revision besides my own.
But if it were to support 3.3v CPUs then I'm not sure where it'd be getting it's regulation from. There's no provisions for a linear regulator, and not enough passives or a coil near the CPU socket (including under the overhang from the heatsink).

That's likely the latest revision of the 486EI. Chips are dated 1994-95 for the most part. The real question is what revision/core BIOS did the unbranded AIR 486EI boards come with?

Also checking ebay, there appears to be a DEC OEM motherboard with the SiS 406/411 and a Phoenix BIOS (also too old for 3.3v and DX4 support). https://www.ebay.com/itm/324708650565

I suspect that Revision 1.5x of the 486EI may have been a special OEM product. Either that, or they sold Rev 1.5x and Rev 2.xx simultaneously with 1.5x being the 5V only version of the board.

It wouldn't surprise me at all if the 3.3V version of the board, if the BIOS is still 6/6/92 and misdetects the DX4 as either 487SX or 486DX2. At least when I read through the 2.2x manual it seemed like "DX4" was just kind of tacked in there.

Chartreuse, when you have 128MB of RAM installed does AMIBIOS count it all? You should have to do something with HIMEM.SYS to make all the RAM available to DOS.
If it's not being counted by the BIOS, maybe there is something different about 72-pin SIMMs (I'm using 30-pin), that requires them to be activated by EISACFG.
There's also the possibility that if the board is a special OEM version, maybe they gimped it a little by removing an address line to limit the RAM to 64MB. Does the PAC60 manual say anything about expanding RAM to 256MB?

Anonymous Coward wrote on 2021-09-05, 00:16:

I suspect that Revision 1.5x of the 486EI may have been a special OEM product. Either that, or they sold Rev 1.5x and Rev 2.xx simultaneously with 1.5x being the 5V only version of the board.

It wouldn't surprise me at all if the 3.3V version of the board, if the BIOS is still 6/6/92 and misdetects the DX4 as either 487SX or 486DX2. At least when I read through the 2.2x manual it seemed like "DX4" was just kind of tacked in there.

It's not like they really need to do much hardware wise to support DX4 and 5x86's beside having a 3.3ish V source. Besides internal caches they act the same as a DX or DX2, just higher internal multipliers.

Sure, in my experience both of those CPUs work flawlessly in my two SiS EISA boards with the exception that they are misidentified by the BIOS. I'm just really curious to see if the CPU detection routine was actually updated, otherwise it would be kind of half-assed for an otherwise high quality product.

*edit*

I just checked the PAC60/61 sales brochure. It says the maximum RAM is 64MB, so I suspect your board may be intentionally gimped. Maybe if you can get the pinouts for the 72-pin SIMM sockets you can check where the address lines are located, and you can check to see if they're all connected. If not, maybe you can use a bodge wire to hook it back up to the DRAM controller.

Anonymous Coward wrote on 2021-09-05, 00:29:

I just checked the PAC60/61 sales brochure. It says the maximum RAM is 64MB, so I suspect your board may be intentionally gimped. Maybe if you can get the pinouts for the 72-pin SIMM sockets you can check where the address lines are located, and you can check to see if they're all connected. If not, maybe you can use a bodge wire to hook it back up to the DRAM controller.

Could be an idea, though surprised it would be gimped but still be fine with 64MB modules, rather than requiring 4x16 instead. Next time I've got the time/energy to pull apart the Dolch to take the motherboard out I will check. Would be weird for the 1.51 board to be lacking address lines that the 1.2 supposedly has.

If the 1.51 was an OEM only version, maybe there was a reason to limit it to 64MB...like not undercutting other products in the company lineup.