IBM HANDBOOK 260 - Manual (Page 90)

72 RS/6000 43P 7043 Models 150 and 260 Handbook
3.2.2.3 Memory Subsystem
The base configuration comes with 256 MB Error Checking and Correcting
(ECC) SDRAM (2 x 128 MB DIMMs).
The Model 260 has an enhanced memory controller running at 100 MHz
memory bus speed. See 3.1.3.1, “Memory” on page 58 for more information
how the memory can be expanded.
Synchronous DRAM
The SDRAM operates faster than conventional DRAM. The SDRAM can
supply data every 10 nanosecond clock cycle once its initial access time of 60
nanoseconds has been satisfied. As with conventional memory, the SDRAM
banks have a period of latency after an access. During this period, the
memory bank would be designated as busy. To achieve better performance,
another memory bank (already precharged) needs to be accessed during that
period of latency. The memory I/O controller uses heavy queueing to be able
to make an intelligent decision on which memory bank to access next. The
controller will queue up to eight read commands and eight write commands
and attempts to schedule all reads to non-busy banks. It fills in with writes
when no reads are pending.
J3 PCI fan connector J4 I/O board connector to
system board
J5 VPD module connector J6 ESP external connector
J7 Internal SCSI connector J8, J9 64-bit PCI connectors
J10 CD ROM Audio J11 Battery connector
J12, J13, J14 32-bit PCI connectors J15 Service processor
external connector
J16 Power connector J17 Diskette drive connector
J18 Tablet connector J19 Power connector
J20 AUI Ethernet connector J21 Cec fan connector
J23 Serial port connector J24 Keyboard/Mouse
connector
J25 RJ45 Ethernet connector J26 Audio in/out
J27 Parallel port connector J28 External SCSI connector
Location Description Location Description