Compaq AlphaPC 264DP Technical Reference Manual page 55

4.3.2 Memdata Bus
There are two memdata buses, each of which is a 256-bit, bidirectional bus between
the Dchips and the memory arrays. Memdata0 connects to arrays 0 and 2; memdata1
connects to arrays 1 and 3 (see Figure 4–1).
Each Dchip sends/receives four bytes of data that it has accumulated to/from the
memory arrays. The connections are as follows:
•
Dchip0 connects to bytes 0,8,16,24
•
Dchip1 connects to bytes 1,9,17,25
•
Dchip2 connects to bytes 2,10,18,26
•
Dchip3 connects to bytes 3,11,19,27
•
Dchip4 connects to bytes 4,12,20,28
•
Dchip5 connects to bytes 5,13,21,29
•
Dchip6 connects to bytes 6,14,22,30
•
Dchip7 connects to bytes 7,15,23,31
4.3.3 Padbus
The padbus is a 32-bit data bus that allows a Pchip and the Dchips to pass data back
and forth. If there are two Pchips, then padbus0 (32 bits) connects to Pchip0 and
padbus1 (32 bits) connects to Pchip1. The chips are connected in the following man-
ner:
•
Dchip0 connects to nibble 0, padbus0 and nibble 0, padbus1.
•
Dchip1 connects to nibble 2, padbus0 and nibble 2, padbus1.
•
Dchip2 connects to nibble 4, padbus0 and nibble 4, padbus1.
•
Dchip3 connects to nibble 6, padbus0 and nibble 6, padbus1.
•
Dchip4 connects to nibble 1, padbus0 and nibble 1, padbus1.
•
Dchip5 connects to nibble 3, padbus0 and nibble 3, padbus1.
•
Dchip6 connects to nibble 5, padbus0 and nibble 5, padbus1.
•
Dchip7 connects to nibble 7, padbus0 and nibble 7, padbus1.
12 February 1999 – Subject To Change
Dchip Functional Overview
Functional Description
4–5