NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/sys/amiga/hardware-part1/5846

Text File | 1996-08-05 | 6.0 KB | 130 lines

Newsgroups: comp.sys.amiga.hardware
Path: netnews.upenn.edu!dsinc!scala!news
From: [e-mail] (Dave Haynie)
Subject: Re: Amiga vs. PC
Sender: [e-mail] (Usenet administrator)
Message-ID: <[e-mail]>
Date: Thu, 29 Feb 1996 19:17:43 GMT
Reply-To: [e-mail] (Dave Haynie)
References: <4glavu$[e-mail]> <[e-mail]> <4h1vmj$[e-mail]>
Nntp-Posting-Host: gator
Organization: Scala Computer Television, US Research Center

In <4h1vmj$[e-mail]>, [e-mail] (Juergen Wahlmann (pg262)) writes:
>In article <[e-mail]>, [e-mail] (Steve Koren) writes:

>|> [e-mail] (Einar Bergsmo Gilberg) wrote:

>|> > In the PC, the mainprocessor does all the work. This is right, isn't
>|> > it?

>|> No.

>To be more specific than Steve, a PC lacks some of the custom chips the amiga
>owns.

It lacks the specific custom chips, sure. Yet a modern PC has much of
the same functionality.

>Floppy and (E)IDE access is done via bios instead of DMA (in most
>cases),

The BIOS is just a program, it's not a transfer mechanism and isn't an
important part of this discussion.

All PClone floppy access is done with the PC's DMA controller. It's
not as elegant as the Agnus DMA means, since it usually runs over a
local bus into main memory at ISA speeds (though some ISA-to-PCI
bridge chips funnel this into fast PCI cycles).

IDE can sometimes be done with this kind of DMA, but isn't usually due
to performance considerations. Interrupt driven, programmed I/O based
IDE and EIDE is commonly used in PCs, and it's the only kind of IDE in
existence on Amigas. Some PCIs have PCI-based EIDE controllers that do
true bus-mastered DMA.

>soundcards are commanded through interrupts,

Interrupts are, in fact, a good thing -- they're used quite heavily in
the Amiga too. PC-based sound cards of today usually have two
different mechanisms: direct digital audio and synthesis. Like the
Amiga, direct digital output is usually DMA driven (it has to be
either DMA driven or heavily buffered). This is typically two channels
at 16-bits/sample rather than four channels at 8-bits/sample. The
Amiga lacks a synthesis chip. Cheap PC cards use cheesy 3-operand FM
synthesis (FM-synthesis is outdated but can yield decent sound if you
work at it -- the venerable Yamaha DX-7 keyboard used 4-operand FM
synthesis), but good ones have real sample-based MIDI synthesis
engines (I have one in my PC which is a superset of the Yamaha TG300
synthsis module -- not as flexible as my outboard Roland, but one hell
of a lot cheaper, with many more built-in patches).

>gfx card support depends on the driver,

That's no different than the Amiga, except there's no official
standard for drivers on the Amiga yet. Virtually all PC-based graphics
cards have blitters that run 10x-50x faster than the Amiga's
blitter. No one seems to have anything like the Amiga's copper, and
even when the graphics card supports some notion of vertical sync, the
PC's OS may not be able to use it. So graphics can be clunky compared
to the Amiga's, though it's very OS-dependent.

>mouse comes through serial port which is a bit fuzzy compared to the
>gameport mouse of the Amiga.

Serial mice have been used successfully on workstations long before
anyone had even hooked a mouse up to the PC. I suspect it's cheap-ass
mice, OS difficulties, or a combination of the two responsible. For
example, I have a real good mouse on my PC at home, and yet the
behavior is markedly clunkier in Windows than OS/2. Don't now
why. It certainly could have something to do with the pointer update;
though virtually every graphics chip on the market nowadays has at
least one sprite or overlay plane for pointer support, there's no
requirement that the OS use it. When you start rendering a pointer, it
begs a number of questions in a GUI environment.

>A PC gfx card lacks sprites in general or, if they are there, they're
>not supported by the OS and the driver. So the mouse pointer is much
>smoother on an Amiga.

Well, there ya go. I heard somewhere that OS/2 uses sprites, perhaps
that's the important difference between the it and Windows. Clearly,
the visible location of the mouse on-screen is what the OS has to deal
with, no matter how smoothly it can track changes to that position. So
it's expensive to update the visual position, the mouse is going to be
clunky, no matter the hardware. An OS problem -- very typical of the
general class of irritations under the heading "Why the PC sucks".

>All in all the Amiga system is much more homogen than the average PC
>which results in a better overall performance relative to processing
>power.

That's true on several levels. The Amiga OS is more highly tuned than
most PC OSs, both in general (since it had to live on slower, cheaper
machines since day 1) and specifically (since there were standard bits
of good hardware in every machine).

>In simple words: a PC needs much more recources and processing power
>to get the smoothness of an Amiga at lower speeds.

That's true. However, in today's market, it gets those resources and
processing power, in spades. You're talking 5x-10x in CPU speed
(perhaps a bit less if you're one of the few, the proud, the '060 card
owners -- a club too exclusive for me, just yet), 10x-50x in graphics,
and even 2x-5x improvement in typical hard disk interface rates,
depending on platform.

But the PC OS place another layer of burden on that hardware. It's not
simply being coded primarily in less-than-optimal C code, it's not
simply having to deal with lots of different hardware. It's things
like required visits to "real mode". Single event queues. Cooperative
multitasking. Non-realtime user interface event processing. The list
can go on and on...

Dave Haynie          | ex-Commodore Engineering |   for DiskSalv 3 &
Sr. Systems Engineer |  Hardwired Media Company | "The Deathbed Vigil"
Scala Inc., US R&D   |    Ki No Kawa Aikido     |     [e-mail]

         "Feeling ... Pretty ... Psyched" -R.E.M.