Path: utzoo!utgpu!watmath!att!pacbell!ames!pasteur!ucbvax!UOTTAWA.BITNET!451061
From: 451061@UOTTAWA.BITNET (Valentin Pepelea)
Newsgroups: comp.sys.amiga
Subject: Re: GVP controller
Message-ID: <8908072207.AA14796@jade.berkeley.edu>
Date: 7 Aug 89 21:53:43 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Lines: 32

Christoph Brand <wizard@accsys.uucp> writes in Message-ID: <437@accsys.UUCP>

> I use now a 2090a, and I don't have ANY problems with it; even with a
> normal ST506 drive, it is AS FAST as the GVP with a Quantum 40S;

Let me give you some insight into that. The GVP controller is actually faster
even though you get lower diskperf times. You see, the GVP controller first
DMA's data onto a local cache. This DMA transfer is not at full speed since
the hard drive simply cannot read bytes that fast. Then the GVP controller
lets the Amiga's processor read the bytes from the cache at full speed, faster
than a DMA fdirectly from the hard disk could do it.

The net result is that the processor therefore spends less time on the data
transfer and is available more often for other concurrent tasks. Unfortunately
this means that there are two transfers occurring, a slow DMA from hard disk
to the cache, and a fast CPU transfer from the cache to internal memory. Other
controllers such as the A2090 and HardFrame DMA directly from the harddrive
into internal memory, thus tying up you CPU much longer.

So if you multitask a lot, you'll want the GVP controller, otherwise the other
controllers are for you. Retry the diskperf benchmark again with a few CPU
intensive programs in the background, you'll see what I mean. Now you know why
all the CS and EE types here on Usenet recommend GVP while the doof dummkopfen
in Deutschland recommend the rest.

Valentin
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