• Comparing a 16-way z900 Model 216 to a z990 model
with sixteen CPs enabled, it is estimated that the z990
model has 1.45 to 1.53 times the capacity of the 216.
• Comparing a 16-way z900 Model 216 to a z990 model
with thirty-two CPs enabled, and the workload execut-
ing on the z990 executing in two 16-way LPARs, it is
estimated that the z990 model has 2.4 to 2.9 times the
capacity of the 216.
Note: Expected performance improvements are based on hardware
changes. Additional performance benefi ts may be obtained as the
z/Architecture is fully exploited.
The z990 contains an I/O subsystem infrastructure which
uses an I/O cage that provides 28 I/O slots and the abil-
ity to have one to three I/O cages delivering a total of 84
I/O slots. ESCON, FICON Express and OSA-Express
features plug into the z990 I/O cage along with any ISC-
3s, STI-2 and STI-3 distribution cards, and PCICA and
PCIXCC features. All I/O features and their support cards
can be hot-plugged in the I/O cage. Installation of an I/O
cage remains a disruptive MES, so the Plan Ahead feature
remains an important consideration when ordering a z990
system. The A08 model has 12 available STIs and so has
connectivity to a maximum of 12 I/O domains, i.e. 48 I/O
slots, so if more than 48 I/O slots are required a Model B16
is required. Each model ships with one I/O cage as stan-
dard in the A-Frame (the A-Frame also contains the pro-
cessor CEC cage) any additional I/O cages are installed in
the Z-Frame. The z990 provides a 400 percent increase in
I/O bandwidth provided by the STIs.
z990 Cage Layout
Model B16
Model C24
Model D32
2C22C3 2C4 2C5 2C6 2C7 2C8 2C9210 211 212 213214 215 2162C1
z900 1C21C3 1C4 1C5 1C6 1C7 1C8 1C9110 111 112 113114 115 1161C1
Model A08




I/O Cage


I/O Cage


I/O Cage
z990 I/O SubSystem