First post, by jakethompson1
- Rank
- Oldbie
There has been past discussion of the ESA 486 motherboards currently manufactured and available new [http://www.esapcsolutions.com/industrial-baby … dram-p-189.html], as a way to build a retro-style system without worrying about parts availability. I built such a system. My opinion was that although this was an interesting exercise and is definitely suitable for an industrial ISA-based system this board is targeted for, expecting 100% faithfulness to and compatibility with an actual 486-era system is likely to lead to frustration; also, it would still be more cost effective to look for new-old-stock or used parts even at inflated prices to build such a system as of today.
Overall positives: Availability/reliability. Onboard floppy/IDE/serial/parallel means no looking for a "Super IO" card. Onboard video means no looking for a VGA card. Supports AT and ATX power supplies (soft-off is not supported; I just placed a jumper cap over the power switch connector and use the rear power switch on the power supply to control power).
Overall negatives: Onboard video compatibility and quirks (see below). The single PCI slot is not really usable in an ATX case due to its position, although I did successfully try a low-profile Ethernet card with the RJ45 jack accessible in the ATX backplate area. PCI bus mastering and ISA DMA conflict may limit the usefulness of the PCI slot (see below).
Specifications
==============
- ESA-486 motherboard w/ 128 MB RAM
- No L2 cache. I suspect this is because the onboard PC100 SDRAM is fast enough to not need one?
- ESS ES1688-based ISA sound card
- 3Com EtherLink III (3c509) ISA NIC
- Cyrix 486DX4 @ 100 MHz
- 8.4 GB IDE hard drive
- SATA DVD-R drive w/ SATA-to-ISE converter
- Tried DOS 6.22 and Slackware Linux 8.0
BIOS
====
The BIOS is a "modern" Phoenix one, definitely not one you would have had on a 486. It can do Ultra DMA, can boot from CD-ROM, handle ISA Plug and Play, etc. Booting from CD-ROM only works with a "real" IDE drive, when I try a SATA drive with a SATA-to-IDE converter, it hangs and I suspect it has something to do with Ultra DMA. If you were expecting a retro style AMIBIOS with memory test tick sounds, this is not it. The only downside is that booting is noticably slower than typical on a "real" 486 machine.
Conflict Between ISA DMA and PCI Bus Mastering
==============================================
As alluded to in the ESA486 jumper instructions [http://www.esapcsolutions.com/ecom/drawings/E … %20JUMPERS2.pdf] and described in the ZFx86 Quick Start Guide [http://www.esapcsolutions.com/ecom/drawings/E … %20JUMPERS2.pdf p. 18] the processor pins for ISA DMA channel #1 and PCI Request/Grant #3. Without understanding all the details, the effect I observed is that you cannot use a Sound Blaster-compatible ISA sound card and a bus-mastering PCI card in the single PCI slot at the same time (I was trying an RTL8139 Ethernet). I suspect this limits the ability to substitute a PCI video card as well while also having a Sound Blaster compatible card, but I have not researched it thoroughly.
Video Compatibility
===================
The onboard PCI video (Silicon Motion LynxEM+ SM712) is obviously not a DOS-era card. There are no Windows 3.x drivers for it, although using the built in SVGA driver and this patch for VMware [ftp://tasha.eecs.umich.edu/Windows%203/Window … 11/vgapatch.txt] seems to half-work, but the video seems slow/unaccelerated.
Plain EGA/VGA DOS-based games seem to mostly work, subject to the video "stretching" issue below. Wacky Wheels works fine. Commander Keens 1 and 4e mostly work. keen1 has shaky graphics regardless of what I try (but is still much better than on some modern ATI cards); keen4e works much better after resolving the "stretching" (below). One thing that does *not* work are the "3D Adventure" Knowledge Adventure titles that I tried; when they tried to launch the video just displays a blank/corrupted screen.
Video "Stretching"
==================
This is the biggest annoyance of this board. The SM712 appears to be a laptop-oriented chip, and by default tries to upscale all output to 800x600, as if it were driving a laptop or other LCD of that size that is incapable of scaling on its own. I managed to find a datasheet for this card [https://www.usbid.com/assets/datasheets/A8/sm712g.pdf] that has sufficient information to reconfigure it to display output on a CRT at "normal" resolution. The VGA BIOS seems to reset back to the upscaling mode on INT 10h, so I actually wrote a TSR (attached) to hook into calls to change the video mode, and re-do the configuration to disable expansion after each mode change. This makes Windows 3.11 in plain VGA mode much better, and resolves all video issues with keen4e, as well as displaying everything on a CRT at normal resolution. The TSR is a work in progress; right now it forces the card to always operate at a dot-clock of 28.325 MHz, producing some weird non-standard timings that probably require a good multisync monitor to handle.
Verdict: A Pentium III with ISA slots (like I posted on here just short of a year ago) would probably be easier to get working (even if there are speed issues) than this machine, although it was an interesting exercise.
