At first blush, I fantasized there would be a hard number, but with all
things IBM, "it depends".
Output Data Rate page 11
The approximate time between two data bytes in a DMA operation is
5 microseconds, assuming that the attached device returns the ‘-acknowledge’ signal to the ‘strobe’ signal immediately. tn addition, the ‘-acknowledge’ signal is 1.0 microseconds wide (the ‘-acknowledge’ signal falls low and not later than approximately 1.0 microseconds after
the rising edge of the ‘-strobe’ line).
To calculate the data rate, the delay from the ‘-strobe’ signal to the ‘-acknowledge’ signal on the attached device side should be added for
each transmission. The transfer rate varies according to the DMA channel
usage of the system.
Tomas Slavotinek wrote:
On 10.02.2023 18:51, Louis Ohland wrote:
So why does software choke on an arbitrated parallel port? Riddle me
that...
Eh, disregard my comment about the pin 12 oddity, that of course relates
to the previously discussed 25-pin SERIAL port. Confirmation bias...
Anyway, there are a few potential problems with the DMA parallel port
(not exclusive to Model 90):
-the connected device does not understand the protocol
-low-level software/driver incompatibility
-configuration/user error (setting the link to ECP or EPP...)
But data transfers between two PS/2s with Type 3 controllers should be relatively trouble-free and pretty fast too!
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