4 Apr
2010
4 Apr
'10
12:28 a.m.
On 2010-4-3 6:24 PM, Artyom Tarasenko wrote:
[...] How is SBUS connected to the IO-MMU? Directly or through a PCI bridge? Quick google search didn't help me to find it. I only found that in the Russian sparc32 PCI machine (Elbrus-90) SBUS is connected through a PCI-bridge. If that's the case in early Ultras too, OBP probably won't be able to tell us much via the serial port connected to the SBUS.
SBUS long pre-dated PCI. The original UltraSPARC machines (Ultra/1, Ultra/2) were SBUS machines, which used a SYSIO bridge instead of PSYCHO. I think the root bus on those machines was UPA (a Sun-proprietary bus). Once Sun's PCI machines came on strong, SBUS pretty much went away.