From: roell@informatik.tu-muenchen.de (Thomas Roell)
Subject: Re: ET4000/W32 and VESA VL-Bus
	<1992Dec28.223727.3569@netcom.com>
	<1992Dec29.191833.1401@Informatik.TU-Muenchen.DE>
	<1992Dec29.224241.21987@netcom.com>
Organization: Inst. fuer Informatik, Technische Univ. Muenchen, Germany
Date: Wed, 30 Dec 1992 09:56:45 GMT

>They do a good DRAM design according to S3 they simulate a VRAM in the
>8c801/8c805 design. I don't know the specifics of their design and I doubt
>that they are going to make it public.

I assume that they simply read the video data for one complete scanline
(1024 or 2048 bytes) within one page cycle (tRAS = 90ns, tCAS= 30ns, but
just guesses, please could someone look the exact thing up in the databook),
which means with a 1024 bytes buffer they would have around 77.6 MB/sec
available (with tRAS = 120ns & tCAS = 40ns, this would be 44.3 MB/sec) at
70Hz refresh rate and 1024x768. This might be actually over the limit the
graphics engine could make use of. The big BUT is still, how are things
looking at 1280x1024, and how are they compared to the 928 which has fully
100MB/sec available ?

>>Will be intresting. Have another benchmark number for people who like
>>really hot boards ... This is the Nth Engine/250, a VRAM based board
>>with a 82C481 on it... Maybe the 928 will be faster ;-)
>
>My expectation is that is going be faster than 120k xstones :-)

Hmmm .... I make no guesses here, but going that high, you'll hit some 
other limits, which are generally called io-bus limits. On the
Nth Engine/250 I computed a xstones rating based upon earlier tests I ran
on other 481 boards and the measured rect500 / scroll500 throughput.
I expected 128k. The reason why this was not reached was that in some
operations, the host to 481 communitcation was simply the limit. Since
most commands go exclusively over io-ports (which are slower than memory
accesses, and awfully slow on the ISA bus), you can do only around
1 million read/writes per second. For some other operations clipping again
got a cpu performance issue. The local bus seems to have solved some
things regarding this io-problem, but some other problems will still
prevent you from getting the top results by just simply linearly
interpolate the xbench results based upon the maximum graphics chip
throuput.

>Who is the chip manufacturer for  the 82c481 and do you have the phone number
>for the board manufacturer of the "Nth Engine/250"?

The 82C481 is from Chips & Technologies (I thought Amanicio would be the
ultimate expert on these things ;-)). The Nth Engine/250 is of course from
Nth. Don't have their number here. This board is way out a reach for most 
people since it is a 2MB VRAM solution with a Bt485 RAMDAC on it. I think
it sells for over $1500 ... Anyway I see the prices dropping if 928 boards
with 2MB VRAM will actually sell (my personal favourite 928 board is still
the ELSA WINNER 1000, which does 1280x1024 non-interlaced for DM 950 in
Germany which is about $600).

>and at 1024x768. I can't because I am stuck with a low resolution monitor.

You can run these higher refresh rates as well. Nobody said that you have
to watch xbench running. Just run XS3 and xbench, but without monitor. The
results will be correct.

>All I want to say is that at $199 the Actix GraphicEngine32 DRAM card is not
>a bad card at all. Also, as much as I want to get my hands on a 928 it was
>delayed two months and I still have to get hold of one to see how it works.
>have the databook and I am all set to got at it.

You are right with the point that a 801/805 is right now generally a better
buy than a 911/924 buy. And since unluckly the 928 boards seem not to be
selling within 2 or 3 months from now they still will be for some time.
But if someone can wait this long, he/she will get a better buy with the
928, which also will do 1280x1024 and 1024x768x16bpp and 800x600x32bpp.
I predict that this will be much more attractive for people that do not
exchange their cards every other week.

- Thomas
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