Chapter 4 PA-RISC Computer Systems - OpenPA.net

PA-RISC Buses GSC
� HSC ( “High-speed System Connect” )
– On several server systems, for example D-Class and K-Class
– Cards are all GSC+
– 100-pin (50×2) male pin & socket with groundplane
– Bulkhead is above the card
– Identical to GSC-M cards except different bulkhead (external connections plate)
� GSC-M ( “Mezzanine” )
– Found on PA-RISC VME computers (74x)
– GSC-1X
– 100-pin (50×2) male pin & socket with groundplane
– Bulkhead is below the card
– Cards are very rare
– Identical to HSC cards except different bulkhead (external connections plate)
CPU attachments
On the two 32-bit LC “Low Cost” processors PA-7100LC and PA-7300LC GSC is the main system bus.
The CPUs integrate the external memory and I/O controller (MIOC) onto the processor (mostly used
with LASI chipsets), with memory and cache directly attaching to it.
1. MIOC, main memory and I/O controller, directly integrated on the CPU
� Execution units and internal caches attach on-chip to the MIOC
� External cache and memory attach to MIOC
2. GSC, system main bus, attaches to MIOC and I/O controllers
� Attaches via 32-bit
� PA-7300LC systems use extended GSC+
3. I/O adapters attach to GSC
References
� LASI chipset
� Some video adapters directly attach to GSC
� I/O slots extend GSC
� Bus adapters, including EISA, VME and PCI, attach to GSC (includes WAX — a modified
LASI — , Dino, and custom chips)
1. An I/O System on a Chip 93 Thomas V. Spencer et al (April 1995, Hewlett-Packard Journal)
93 http://www.hpl.hp.com/hpjournal/95apr/apr95a4.pdf
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