Sounds awesome. DIP switches for Ram config sounds odd! Looking forward to the photos.

Until I get some photos up, here are some shots from the ebay auction

Wow that is a massive motherboard! Bigger than my Dual Pentium Pro.

Nice system. I've been kinda wanting to play with an EISA system, but could never really justify it. The boards are hard to find (or rather,good ones are hard to find.. there seem to be plenty of those POS HiNT boards around), plus I'd have to track down EISA cards too, which makes for a rather significant investment.

TBH, though, what caught my eye the most is the hard drive setup... an ISA card that supports PIO4/DMA2? How the hell does that work? I've seen a couple that purport to do PIO2, but even with an overclocked ISA bus, 8-10MB/sec is sorta pushing the practical limits of throughput.

You mentioned maybe getting a SCSI drive, and yeah, that's the way I'd go. I'd personally get a SCSI CD-ROM drive too and lose the IDE altogether. However, I'm not sure if the 2740W supports >8GB drives... not that it would really be a huge loss, even one of the common-as-dirt 4.5GB drives would be more than enough for a 486, but it's something you may want to check on before you go buying hard drives.

The AHA-2740 series BIOS supports drives right up to the 8.4GB INT13H limit. Sadly it doesn't support CD-ROM booting, and I can't seem to get SBM to see my IDE CD. As for the I/O card, its a SIIG SC-JEE012 with a giant "Enhanced IDE" logo on it. Period documentation states it does DMA transfers up to 8.3MB/sec

http://web.archive.org/web/19980214041955/htt … de/eideenha.htm

The operating mode is what HDAT2 reports for the drives under plain DOS. I don't know if its accurate or not.

I hear you about the lack of good EISA boards. It seems wiredforservice on ebay has the market cornered and won't part with them. There is an older EISA only Mylex MAE486 board up, but someone pulled the BIOS, keyboard controller, and the two RTC modules off of it! I found a copy of the BIOS online, but getting that board up and running would be costly if one can't find the Dallas chips for it.

Ah, OK... from what I can gather from the documentation you linked, it looks like the VLB version is capable of PIO4/DMA2 (16.7MB/sec), but the ISA version is a bit more limited... it doesn't state clearly what modes it supports, but 8.3MB/sec is the spec for PIO2 and single-word DMA2. Still, though, that's not bad at all for an ISA card... most don't even have the option for higher speeds, it's just the original PIO0. And it wasn't until the later '90s that IDE drives came out that could push more than 7-8MB/sec sustained anyhow, so 8.3MB/sec is certainly adequate bandwidth for that sort of machine.

About the SCSI CD-ROM, I hunted down the manual for the 2740-series (here, if you haven't already found it), and according to that, there should be an option to enable CD-ROM booting through the ECU, under the BIOS configuration section.

I ran across that revision of the manual (dated 1996). It seems to be from a later version of the card, but all of Adaptec's EISA config and overlay files simply don't show the option. I was hoping for a ROM upgrade, but the ROM Adaptec has posted for the cards is older then the one my board came with! (2.10 is posted, I have 2.11)

Hm... strange. Maybe somebody more familiar with those cards can offer some insights... I think there are a couple people on here who have them.

Of course I suppose the other question is... when would you actually need to boot from a CD on a 486? Everything CD-based I can think of that would be 486-friendly either isn't bootable to begin with, or can be started from a boot floppy.

Got the 100Mhz DX4 overdrive today, so here are some SPEEDSYS numbers for this board.

This program seems to ID the HD running at PIO3/DMA1, reasonable given that its an ISA interface. Testing the CF card lead to some amusing results. It pegged the HD speed bar on the bottom, but actual linear read speed isn't much faster then the HD I got.

Great looking motherboard. It seems it uses some custom Micronics chipset. What are the Intel chips near the CPU socket?

I'll doublecheck, but thats likely the Intel 82350 series EISA chipset. One of Intel's first chipset efforts date back to 1990.

How much did this beauty set you back? I've always had an interest in EISA systems but could never justify the effort and cost. Any serious effort to source an EISA system fizzled when I found a stable super fast PCI socket 3 board.

Is that a RTC module in the first image? Is it compatible with the Dallas 12887 units? If not, are they difficult to find new? What is the production date on your RTC? I've never seen an RTC battery last more than 18 years. You can get new production date code Dallas 12887 RTC's on digikey for a pretty penny ($10+).

The RTC chip is a Benchmarq bq3287mt, which is pin compatible with the Dallas chip and still holds a charge! Replacements are still made by TI. RTC batteries can last a long time in some cases. My circa 1987 Apple IIgs still holds a charge with its "5 year" lithium battery.

The board was $50 after using ebay's "best offer". You have to find a seller who is willing to negotiate prices though. wiredforservice doesn't from what I can see, even though some of the equipment is clearly damaged and noted as such in the auction listing.

EISA boards are certainly odd for the most part. Many of them are seemingly 1991 designs even though they had VLB slots and Overdrive sockets tacked on. So we get stupid limitations like no write back L2 cache, and 16MB limits for BIOS shadowing (which is ridiculous on a 32bit machine!). The most modern boards seem to be based on the Opti chipset. The AIR 486EI seems to be the best board, sporting a full 5v/3.3v Socket 3 design. Don't know if it does write back L1 cache though.

Forum user 'Anonymous Coward' is the guy to ask about EISA 486s. He seems to have one of the better configured EISA 486s still out there and has tested many EISA cards. He has 1 MB cache on his board and 128 MB RAM, etc. You can check it out here,
My Ultimate VL/EISA 486

What is the longest you've seen a Dallas 12887 RTC last? The longest I've seen a 12887 last is in a HOT-433 board I have. It has a 1994 date code and may still work, but in the past few months, the time keeping has slipped quite a bit. It was off by several months at last power up and is probably entirely non-functional now.

I think most of us don't even look at the wiredfor* listings anymore. One glance at those crummy cell phone quality photos and I move onto another listing. From what I've heard, a lot of what he sells is defective or mis-labeled.

There are some other EISA boards, like the Everex 'Step 486 EISA' series, Gigabyte GA-486SA/486TA and the AMI Enterprise III, that use the SiS EISA chipset and are a fair bit more modern. Finding one is a bit of a challenge, but they are out there... a few members here have them, and yes, Anonymous Coward is the one to talk to about those boards.

But the reason a lot of the EISA boards seem to be 1991/1992 designs, is because they are 1991/1992 designs. VLB came around in '92, as did the overdrive sockets (even though nothing actually made use of 'em until quite a bit later). The limitations you're talking about are pretty standard for early VLB boards, so it's really no surprise that they also exist on consumer-level EISA boards. Remember, the Micronics board you have wasn't really a business-class board, it was primarily used in Gateway's upper-end home system... something akin to the Dell XPS series of today.

And don't bother getting worked up about the lack of write-back L2 cache. That's majority of all 486 boards... they didn't even start making 486-class processors that supported it until mid-late '94, which was getting to be near the end of the 486 era, and it never became a common thing on VLB or EISA boards because VLB and EISA were on their way out in favor of PCI. Write-back L1 is worth having, but you're not really missing much performance with write-through L2 on a 486 machine anyhow.

About wiredforservice/newsgroups... that clown is one of the primary reasons I wish eBay would implement a seller blacklist, so I wouldn't have to go through the extra steps to filter out all his crap listings every time I make a search. Him and that guy that uses the same track runner picture on all his listings.

Yes, this board was used in the Gateway 2000 4DX2/66E in that giant tower case they used. Regarding L2 cache, I coulda swore my 486 purchased back in 1993 had write back L2 cache.

As for clock chips, those Dallas modules were failing in the late 90s, on machines that were only 5 years old. I hated fixing those things, usually we just replaced them. We weren't afraid of soldering.

Also, are the memory benchmark numbers in-line for a WT L1 cache DX4 100Mhz? Its been awhile since I had a 486, although I could compare numbers with my newer SiS based Soyo SY-25N board.

Yeah, your numbers look decent... they're actually not too bad even compared to some of the cheaper boards that do support WB cache.

As far as having a 1993 board with WB L2, it's certainly possible there were boards that technically supported it, but there wouldn't have been any processor at the time that could've used it. The standards were a mess during that period... board manufacturers were scrambling to support all sorts of features that were "just around the corner," that ultimately ended up being delayed or cancelled entirely. The POD is probably the best example of that, it was originally expected to come out in '93, and everybody started adding the sockets and BIOS functions to support it, but the chip didn't actually get released until '95 and by that point the specs had been changed enough that it didn't work in some of the early 'Overdrive capable' boards.

About the Dallas chips... on some boards it may be possible to solve the problem once and for all by converting 'em to use a DS1285/12885 and an external battery. Your board looks like it could be a candidate for that, I see unpopulated spots for a battery and 32.768khz clock crystal. You'd have to work out the values on the other associated components, but I'd imagine it's based mostly off some sort of reference design so it'd probably be doable just by looking at datasheets. I've thought about doing something similar on a Biostar board I have, but I haven't had the time to really investigate it much.

The board I had in 1993 was a "Typhoon 486" based on what the manual said. TH99 says a "Target Micro" made it, but the board layout doesn't look like I remember. The board was from late 92-early 93 if I recall, the AMIBIOS was dated 06/06/92 and it lacked a ZIF socket. I do have an old VHS video of it booting, but the BIOS string is hard to read and what I can decipher of it, the vender number doesn't appear on any of AMI's lists.

Anyway, I remember many vendors advertising WB L2 cache based 486 systems in Computer Shopper at the time. They all touted the Overdrive Ready bit too.

Just a guess, but I suspect the two things probably went hand-in-hand, since AFAIK the Overdrive was always specced to support WB cache since its original inception.

OTOH, that was also the era when a bunch of the fly-by-night Taiwanese manufacturers would blatantly lie about specs, and "Typhoon 486" sounds suspiciously like one of the generic boards that would typically be guilty of such a thing. So that's a possibility too.