ISA bus 8514/A?

During the development of the 8514/A, IBM clearly had ISA-based adapters. A proof of this may be found in the source code for the Windows 2.x setup program (part of the Binary Adaptation Kit, or BAK), which among other things detects the graphics hardware so that it could select the appropriate graphics driver. The comment in the source code is quite clear:

The way we [detect an 8514/A] is to first check if we have a PS/2 or compatible with a micro-channel BUS. Then, we proceed to put each adaptor into setup mode, one at a time until we’ve done all of them. Then, we read the pre-defined “adaptor ID” word. If we find the adaptor ID, for the 8514, we can conclude that it is present.

This algorithm will NOT work for the experimental 8514 boards which were made for “XT-BUS” machines. Since these were never released to the general public, we can feel safe that it’ll only be of the slightest inconvenience that this type of 8514 cannot be detected.

One has to wonder whether the mention of “XT-BUS” should really have been “AT-BUS”. Since the 8514/A register interface is heavily oriented towards 16-bit words, it is somewhat unlikely that PC/XT systems with an 8-bit bus would have been supported.

At this point in time, it is anyone’s guess whether the ISA bus 8514/A boards were a planned but never-released product, or just a prototype that could be provided to software developers before PS/2 machines were available. The term “experimental” could be understood either way.

Interestingly, the Windows driver itself (8514.DRV) does not appear to have any dependency on PS/2 or MCA. It almost certainly worked with ISA-based 8514/A clones. This is true of the 8514/A drivers for both Windows 2.x and Windows 3.x.

This entry was posted in Graphics, IBM, PC hardware, Windows. Bookmark the permalink.

7 Responses to ISA bus 8514/A?

  1. Richard Wells says:

    An 8-bit (i.e. for XT) 8514/A display adapter would match the 8-bit VGA display adapter that IBM shipped in 1987. The IBM VGA display adapter included a header that as far as I know never had any product to attach to. Admittedly, with an 8-bit interface, the resultant setup would be very slow and probably not worth the close to $3500 that IBM would charge for the VGA display adapter plus 8514/A and 8514 monitor.

  2. Michal Necasek says:

    The 8514/A might not have suffered too terribly from the 8-bit interface as there’s no need to ship everything over the system bus… then again, I doubt the folks who did CAD back then had any interest in using XTs. So yeah, such a product probably did not make sense.

    Interesting about the VGA adapter header. Was it anything like the feature connector used on non-IBM VGAs later?

  3. Mr. Argent says:

    I don’t know if this clarifies much but I’ve been working on one of those cool two-foot-tall Gateway 486 boxes and the OEM Windows 3.1 setup diskettes default to 8514 mode even though the system itself has an ATI Mach 32 in it.

    This might be of use as an example of the 8514 driver’s lack of dependence on IBM standards in action on mass-produced hardware?

  4. Michal Necasek says:

    Hard to say. By the time Windows 3.1 came out, 8514/A clones (notably ATI mach8 and mach32) would have been considerably more widespread than the original IBM part.

    The Windows 3.x 8514/A driver certainly does not make any assumptions about buses or anything like that, but it’s hard to say if it was written that way from the start (possible) or adjusted to work with clone hardware (entirely plausible).

  5. r.stricklin says:

    For what it’s worth the standard Windows/386 8514/A driver works fine on ISA-bus 8514/A clones like the Mach32 and the Western Digital Paradise 8514/A Plus.

    There’s an 8514/A driver in the IBM-supplied Windows 1.04 kit for PS/2, but even on an MCA machine it’s hard to tell if it actually does what it implies on the tin since the display mode is 640x480x16 and consequently indistinguishable from what you’d see with the built-in VGA. So I haven’t tried it on an ISA clone board.

  6. Michal Necasek says:

    I can confirm that Windows 3.1 runs with the built-in 8514/A driver on a PCI mach32 without any tweaking. The driver does not rely on MCA POS for detection and does not use any MCA or PS/2 features at all.

    I don’t have any WD 8514/A clones but have one or two C&T chips.

Leave a Reply

Your email address will not be published. Required fields are marked *