Re: AP-67 82C37 Application Note

On Mon, 26 May 2008 10:13:28 +0200, "Wolfgang Kern"
<spamtrap@xxxxxxxxxx> wrote:

<snip>

OTOH, CPUs are usually much faster than the RAM, so DMA-cycles may
not be any faster than REP:MOVS and the CPU cannot do very much
during it anyway, so the question is: why ?

As I recall, the original 8237 and 82C37 were limited to 5 MHz, which
was fine on the 4.88 MHz IBM PC. But then the AT came out with a
faster bus (first 6, then 8 MHz) and DMA had to be throttled back to
half-speed in order to stay under 5 MHz. Data acquisition cards that
had previously used DMA for I/O now found that string instructions
were faster.

Don't know how the speeds of the 8237 family might have increased over
the intervening decades.

Best regards,


Bob Masta

DAQARTA v3.50
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, FREE Signal Generator
Science with your sound card!

.

Relevant Pages