10
Dec
15

Mainboard: Generic Socket 3

Today’s motherboard is a bit of a mystery as it doesn’t have any obvious markings that identify who made it or a model number. It is a late socket 3 board that supports fast 486 chips and the Pentium Overdrive. Socket 3 is interesting as it is where the CPU designs started to really diverge depending on the manufacturer, but the chips all still ran on the same boards. It didn’t last as long as the later socket 7 standard as it came part way through the life of the 486.

Here is the board in all it’s glory (or infamy). There are a few things to note about it, firstly it must be a later board as it has a PCI Bus instead of a VLB and only ISA slots. PCI wasn’t common on 486 boards, and some had early buggy versions of it (or the BIOS), but this board could be running a later 2.0 or 2.1 version of PCI which had the kinks worked out. Judging by the date codes it was made in late 1995.

Also you’ll note it has a very integrated chipset made by ALi (Acer Laboratories incorporated). I usually have seen their chipsets on boards that are in brand name PC’s rather than your usual beige boxes. They also ended up on value boards like SiS chipsets used to, but had better software support when that was required. This particular chipset is more integrated than many early Pentium boards, and is much smaller. It could have fitted a smaller chassis than normal.

Like other socket 3 boards this one has some cache on board in the form of the SRAM chips. There were a few dodgy manufacturers that put fake chips on their boards instead, but I don’t think this is one such board. To start with this has a genuine ALi chipset, where as the dodgy brothers boards often had a generic chipset that wasn’t much chop. To hide the fact they had a chipset like that they stuck stickers with the chip markings of other manufacturers over the laser etchings.

These cache chips are marked as Writeback, which turns out to be the chip maker rather than the cache type. I couldn’t find a datasheet, but from the basic information available they are basically SRAM chips arranged in two banks. There are an odd number of chips, one of which I’m guessing is used for parity checking.

Ugh look at the arrangement of the configuration jumpers. From a technicians standpoint this is horrendous. There is no silk screen for most of the jumpers, so I have no idea how you’d configure this board without the manual. Luckily the front panel jumpers are labeled, and the voltage selection for the CPU is labeled. Like many Socket 3 boards, this one will take both 3.3V and 5V CPUs.

This is the only mark on the board that identifies anything about it, apparently it is version 1.2A. I got this board from an uncle that had it in a beige case, and that unfortunately was generic, so I can’t even chase a possible manufacturer that way.

It might have been an ok board from an end users perspective, I got this board with a 100Mhz 486DX4 chip in it, and it did run Doom exceptionally well. I even was running DSL (Damn Small Linux) on it for a time. It had something like 16Mb, but probably could have taken more. It was unfortunately at the end of the DOS era, so it would have depended on whether Windows 95 was on it or MS-DOS. Windows 95 did run on 486 machines, but not really all that well.

It used to work some time ago, but something went wrong with the chipset as it doesn’t detect it’s memory properly anymore and it doesn’t boot. I’ve been thinking I’d like to have a go a reflowing some of the solder connections as I suspected some dry joints. Unfortunately I don’t have a heat gun, so that will have to wait. One thing I really liked is the use of a coin cell for the RTC and CMOS settings, so I might have to attempt a repair on it one day.

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9 Responses to “Mainboard: Generic Socket 3”


  1. 1 goughlui
    December 10, 2015 at 4:04 pm

    The chips do look a little odd with what appears to be laser/pressed markings rather than printed/painted, although the odd number is probably because there’s a “tag” store for the cache. That’s basically one extra bit to say whether the cache pages are valid or not if I recall correctly.

    • December 10, 2015 at 5:27 pm

      That would depend on what type of cache is being used, write back or write through. The write back cache would need such a flag to know which entries haven’t been stored in main memory yet. The write through cache doesn’t need this as the memory and cache are updated synchronously. Given the cache is controlled by the chipset here we’ll never know which it is (not without the manual anyway). But yeah it could be a tag for the cache rather than parity,

      I figured it might be parity because that was a feature of some 72 pin RAM. Obviously not all the actual modules had the parity chip fitted, but some did. It would also have the benefit of warning the chipset of faults with the cache memory.

  2. December 11, 2015 at 2:31 am

    I agree the cache chips look suspicious with the laser markings. They actually look like the fake chips on my infamous M919 board. also cache on early boards that are soldered directly to the board are never a good sign. its usually not a bad sign on a S7 board but on s3 its usually cause the manufacturer was to cheap to spring an extra 3 cents or whatever it cost for socketed chips. only way you’ll know for sure is run cachecheck on it. Ive had plenty of older boards that tried to fool me with fake cache and fake declarations of “256 l2 cache” on POST.

    • December 11, 2015 at 10:31 am

      Unfortunately the board doesn’t run anymore, so I can’t check that way. I did look up the chip markings and they do appear to be high speed SRAM chips. I suspect they are genuine cache chips, because many of the cheap boards with fake cache also had fake chipsets (many marked with stickers instead), also the board performed quite well with a 486dx4 100Mhz. It played doom quite well indeed, I can’t know for sure, but almost certainly better than a machine without the cache.

  3. December 11, 2015 at 12:05 pm

    Something that I forgot to mention (and couldn’t show) is that the board had a BIOS setup program modeled after windows! You could even use your mouse to navigate it. It wasn’t as intuitive as i would have liked, but it certainly was interesting.

  4. 6 Dave
    April 5, 2016 at 8:15 am

    Looks similar to one I have from the same era… mine definitely was a win95 machine, and it did well, back in the day, for the office tasks I had for it. I moved on to other hardware, and later loaded this with an earlier RedHat linux to play with, then set it aside and forgot about it. I just fired it up today, and with some guessing even found my Linux root password … hah … (says something about something, given I last touched it about 10 years ago). Like you, I cannot determine the maker. the closest I have found is the M912 ver 1.4. Mine says 1.3, but given the differences it may be a different model. If interested, I’ll send a pic of it. I just started exploring today to see a) if I could find information about it, b) if anyone was still using these antiques, c) if there was any hint that some might be interested in obtaining one. I see some similar boards being offered on ebay.

    • April 5, 2016 at 9:45 am

      Thanks for the comment! It’s interesting to hear that yours ran win95 quite well, as I’d seen a few 486s that certainly didn’t run it very well. It could be down to the newer bus architecture (PCI based bus) verus the older standards many 486 machines had.

      If you have a picture handy it would be interesting to see another one, are there any clues to the manufacturer in the case? Information on the board might be non-existant if the manufacturer went broke, that is if we ever identify who made it. Lots of people are still using old machines like this (and older) many for playing MS-DOS games in an authentic way. There is a thriving retro computing scene if you look in the right places. For old PCs the VOGONS forums seems the place to go for talking about these old beasts.

      Sparcie

  5. 8 Dave
    April 5, 2016 at 11:52 am

    Not figuring out how to attach a pic or pix for you.
    See this board, which seems to be a close sibling/cousin though.
    (http://motherboards.mbarron.net/models/486vlb3/m912v14p.jpg)
    .
    mine does have differences…
    but other than these few they are just way too similar:
    NO PCI,
    One Less Slot,
    slightly (very slightly) different chip layout.
    UMC Chipset,
    slightly different jumper layout.
    .
    Interesting thing about these boards, to me, is that except for keyboard
    all IO, including FDD and ATA (HDD and Optical) was handled through the ISA cards…
    in my case one of the ISA plus VLB slots.
    I bought it with a modem card, and later added other cards.
    (I may still have the original documentation somewhere, but no-idea-where.)
    .
    I found a serial number on the board (sticker on one of the ISA card slots),
    but no model number, or maker that I can tell. Sticker says made Oct of 1996.
    It came loaded with Win95… (on a Quantum Bigfoot, 5.25″, 6gb hdd.)

  6. April 5, 2016 at 3:05 pm

    It’s odd that it didn’t have more integration, but perhaps your board was designed for low cost or the chipset lacked the features. That would also explain using VLB instead of PCI which was starting to take off in 1996. It’s also probably an older design adjusted for what was available at the time.

    The board in the picture in the link is older than both (mid 1994 from the date code on the chip) so if yours is similar it’s almost certainly an old design that continued production.

    if you haven’t already I’d suggest showing the guys over on the VOGONS forum (http://www.vogons.org/) to see if they know.


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