Baoran wrote on 2020-11-14, 10:58:

I would be curious about what is the lowest realtics value someone has gotten in the doom benchmark using an ISA card and while having standard isa bus clockspeed.

I've seen this discussed in other threads. I don't remember the realtic numbers but I think the best isa cards typically reach 20fps. I remember someone with a DX5-133 managed to get 24fps.

BinaryDemon wrote on 2020-11-14, 11:15:

Baoran wrote on 2020-11-14, 10:58:

I would be curious about what is the lowest realtics value someone has gotten in the doom benchmark using an ISA card and while having standard isa bus clockspeed.

I've seen this discussed in other threads. I don't remember the realtic numbers but I think the best isa cards typically reach 20fps. I remember someone with a DX5-133 managed to get 24fps.

Thanks. I was getting around 20fps in my super socket 7 system as well.

Baoran wrote on 2020-11-14, 14:05:

[Thanks. I was getting around 20fps in my super socket 7 system as well.

So pushing 320x200 @256 colors, 20 times a second, means that Doom would have to push ~1.25 MB/s to the VGA card, yes?

Is that an inflection point on the ISA bus where pushing the extra frames require an increasing CPU load that prevents rendering additional frames?

douglar wrote on 2020-11-14, 15:52:

Baoran wrote on 2020-11-14, 14:05:

[Thanks. I was getting around 20fps in my super socket 7 system as well.

So pushing 320x200 @256 colors, 20 times a second, means that Doom would have to push ~1.25 MB/s to the VGA card, yes?

Is that an inflection point on the ISA bus where pushing the extra frames require an increasing CPU load that prevents rendering additional frames?

That is where the vintage 8085 signaling hardware breaks down with the typical 5 ISA cards on the bus.

For a disk or memory device the upper limit is around 3mb/s

If you “violate” proper bus design and don’t follow the normal ISA standards you can almost achieve 8mb/s for a short period on specialized hardware.

douglar wrote on 2020-11-14, 15:52:

So pushing 320x200 @256 colors, 20 times a second, means that Doom would have to push ~1.25 MB/s to the VGA card, yes?

Is that an inflection point on the ISA bus where pushing the extra frames require an increasing CPU load that prevents rendering additional frames?

It is a bit more complicated as Doom is using several framebuffers and there is algorithm to avoid transferring data that hasn't changed between frames (such as HUD overlay). But essentially bus speed (16bit writes to VGA RAM) is the bottleneck of DOOM performance on a reasonably fast 486 system.

They served there purpose for a very short time. From about 1993 to 1996 was when they where most popular but the
Pentium CPU and Windows 95 made it obsolete.

They where mainly used with DOS and Windows 3x computers.

My take is that a speed upgrade from ISA was desperately needed. There were actually many different standards out there. VLB and Microchannel are some of the more well known ones.

Part of it was also the R&D costs and the potential (and probable) market penetration of whatever standard any particular company would prefer to see gain traction.

VLB was relatively easy and cheap to implement and was a good stop-gap measure until a better product could become available (which was to become PCI, and later (though somewhat unrelated to this discussion here) AGP).

Things went very fast back then. We don't get such changes this fast anymore. 3 years back then was a long time. VLB had served its purpose.

As to whether VLB cards were ever good? The thing is (in my opinion of course) that I've always found contemporary graphics cards of any given usual motherboard to be somewhat lacking. This is why I've always preferred to build systems which would usually havea graphics card that was at least 1 or 2 generations more recent than the motherboard.
With VLB there is so much fewer choices regarding what graphics cards to pick, so whatever board you're gonna pick, you'll probably end up with a graphics card that is barely any more recent compared to the motherboard (noticeable exception being 386 VLB motherboards, or perhaps 486 boards with the oldest/slowest 486 CPUs).

I mean the graphics cards were often the same, with there being both a VLB and a PCI version (and sometimes even ISA). And apart from the standard VLB issues we're left with, having so little choice compared to PCI does make it a rather more poor array of choice when it comes to having good VLB cards for any matching hardware.

Hardware in itself (when looking at how 'fast' any given piece of equipment is) is not fast or slow. it is only when compared to something else (another different part of hardware which it itself is compatible with).