> In one of your posts in OS2DF1 you mentioned that some video cards
> need a memory aperature on ISA machines and that this was a problem
> if the machine had 16 Mb or more of RAM. Well, I'm in the market
> for a video card too and have an ISA machine with 20Mb of RAM and
> was wondering what a memory aperature was and what problems the
> high memory caused.

The problem seems to be limited to the ATI Ultra Pro (VRAM) and Ultra
Plus (DRAM) and (I think) the P9000 (Diamond Viper). For best
performance they need a linear memory aperature of at least 2Mb that
is 2 Mb above all physical RAM (which must be contiguous). On an ISA
bus that aperature must be below the 16Mb line because of addressing
limits on the ISA bus. That means the memory aperature can't be used
with more than 12 Mb of RAM. An (expensive) EISA card solves the
problem. (Having an ISA card in an EISA slot doesn't help.) VESA
Local Bus (VLB) apparently doesn't solve the problem either, at least
on the ATI.

BTW, I don't think the memory aperature affects the performance using
IBM's 8514/A drivers, only ATI (Windows and presumably Windows NT
beta) drivers. However, the Ultras are slower and more limited in
8514/A mode than they are with native ATI drivers. Then again, ATI
has yet to release even 16-bit drivers for OS/2 (they're in beta), and
the release of 32-bit drivers is probably at least 3 months away.
Note also that ATI is known for buggy drivers.

One advantage of ATI is that the Mach32 chip has hardware support for
Windows motion video playback; it's unknown whether this will be
available for OS/2. Also, although ATI prices have been high, it
slashed prices 30% last week.

> Do you know much about it or know where I can find that
> information?

GO ATITECH and scan the messages. In short, ATI claims only a 5%
slowdown when the memory aperature is disabled, but there have been
several reports of big performance losses and an inability to use
24-bit color; ATI's response is that it is still working on optimizing
its Mach32 drivers. GO DMNDONLINE for Diamond information. (Tseng
ET4000W32 information is available in the same forum.)

> Also, if you've made a purchase yet, which card did you decide on?

From all that I've learned, the choices as I see them (in increasing
order of performance and to some degree cost) are:

* CatsEye/X: An ISA XGA-2 card using the IBM chipset that probably
has the best driver support by far under OS/2 2.1. Speed is
reportedly good, but not as fast as the latest S3 accelerators, not to
mention the Weitek P9000. Color depth is limited to 8 bits (static
64K color pallette). $250 + $9 shipping by mail order.

* Diamond Stealth 24 (S3 801/805 w/DRAM) or equivalent (e.g., Orchid):
S3 is well-supported in drivers in most environments -- there are
already generic NT beta drivers and soon to be generic OS/2 drivers.
Both Diamond and Orchid release their own tuned drivers, which are
expected in a month or two. The 801/805 cards are a good deal faster

than the old fast S3 911/924 cards (even unaccelerated), and are a
real bargain thanks to the use of 1 Mb DRAM (about $170 on the
street). Both ISA and VLB versions. 24-bit color in 640x480, 16-bit
(64K) color at 800x600, and 8-bit (256) color at 1024x768.
VESA-standard refresh rates at all resolutions.

* Diamond Stealth Pro (S3 928): A bit faster than the S3 801/805, but
quite a bit more expensive (about $250 on the street with 1 Mb) due to
the use of VRAM; the speed difference only really shows up at the
highest resolutions (up to 1280x1024) and refresh rates (VESA-standard
at all resolutions). Upgrade to 2 Mb ($80-100) allows 24-bit color in
800x600, 16-bit (64K) color at 1024x768, and 8-bit (256) color at
1280x1024.

* Tseng ET4000W32 (a few smaller suppliers and the Hercules Dynamite
expected soon): Fastest DOS and dumb frame buffer performance, and
accelerated Windows performance is claimed (unsubstantiated) to be
faster than the S3 801/805 and even comparable to the P9000. The best
non-accelerated driver support of any card, but accelerated drivers
for OS/2 are at least 2-3 months away (currently in early alpha);
likewise NT. Also a real bargain, with prices about the same as the
S3 801/805. However, VESA 70+ Hz refresh rates are only supported (by
the Hercules) at up to 8-bit (256) colors; 16-bit (64K) and 24-bit
(16M) color are limited to 60 Hz. Bear in mind that even a dumb frame
buffer like the Tseng ET4000 performs much faster on VLB than on the
ISA bus, giving perhaps 2/3 of the speed boost of an ISA bus S3
accelerator (though much less than a VLB accelerator), so a VLB Tseng
ET4000W32 should give at least respectable performance even without
accelerated drivers.

* Diamond Viper (Weitek P9000) or equivalent (e.g., Orchid): This is
a screamer, about 40% faster than the S3 928 as measured by WinBench
3.11, although the real world performance difference is smaller.
Plays enlarged motion video at 800x600x64K effortlessly (as tested on
a DX2-66). Thanks to top performance and 2 Mb of pricey VRAM
(resolutions up to 1280x1024x256, all at VESA-standard refresh rates),
at the moment it's about $400 or more on the street. OS/2 drivers are
in alpha (shown by Diamond last month at COMDEX and just made
available for download by Orchid) and also due to be released in 1-2
months; NT drivers are supposed to be out in about the same time
frame. Early cards were a bit buggy, so be sure to get the latest rev
(chipset and BIOS).

* IIT X-14 (Hercules Graphite) and X-15 (Orchid Celcius). The X-15
(an improved version of the X-14) is claimed by IIT to be the fastest
current accelerator. (Orchid confirms that it is a bit faster than
the P9000, which Orchid also sells.) However, OS/2 driver support is
very limited -- only 800x600x256 and 1024x768x256 alpha drivers for
the X-14 (that don't support the X-15), with no word on when more
drivers will be made available. The X-14 and X-15 are NOT fully
XGA-compatible, so XGA drivers won't work. Another problem is that
the VLB version of the Hercules Graphite is only FCC Class A.

My research has convinced me that WinBench is NOT an accurate
predictor of real-world performance. Certain chips and/or drivers
have been optimized to win the WinBench contest without providing as
much real-world performance as the numbers would suggest. Caveat
Emptor.

The bottom line is that *any* of these cards (even the ISA ATI) are
reasonable choices, depending on what you want and what you can
afford. If I were going to run OS/2 all the time and I wanted the
best possible support, I'd go with the CatsEye/X. If I wanted to run
*anything*, I'd go with the Tseng ET4000W32. If I wanted the best
bang for the buck I'd go with the S3 801/805. If I wanted the
absolute top performance (and could afford it), I'd go with the Weitek
P9000, IIT X-15, or maybe settle for the S3 928.

I haven't made a final personal decision yet -- I'm agonizing between
the Orchid F1280+, P9000 and X-15.

-John Navas
70244,2046
6/3/93