At 22:10 +1100 11/23/05, Kennedy, David wrote: >We all know that SE/30 PDS cards can be stacked if one of those cards has a >pass-through socket. But this makes me wonder how the PDS really works.
PDS stands for Processor Direct Slot. There may be some buffering but the general concept is that a PDS device has access to the actual pins on the microprocessor chip. Software running on the processor access memory locations that are not present in RAM but the PDS "client" recognizes the address and provides or accepts data as required. The speed of the PDS is the same as the processor and there are no impedance matching line drivers for the likes of a few inches of cable. The loading limit on the lines is only what the processor supports. In short, it's a cheap way to get a bit of expandablity, a bit like the old spring clip that connects to the pins of a 48 pin DIP 68000. -- --> The best programming tool is a soldering iron <-- -- Compact Macs is sponsored by <http://lowendmac.com/>. Support Low End Mac <http://lowendmac.com/lists/support.html> Compact Macs list info: <http://lowendmac.com/lists/compact.shtml> --> AOL users, remove "mailto:"; Send list messages to: <mailto:[email protected]> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive:<http://www.mail-archive.com/compact.macs%40mail.maclaunch.com/> --------------------------------------------------------------- iPod Accessories for Less at 1-800-iPOD.COM Fast Delivery, Low Price, Good Deal www.1800ipod.com ---------------------------------------------------------------
