Power Mac 7300-series


We appreciate your technical corrections and comments !

The PowerPC 604e-based 7300-series shares a common logic board (aka "TNT") with its predecessors, the PowerPC 601-based Power Mac 7500 and PowerPC 604-based 7600. With eight (8) DRAM DIMM slots and a 64-bit data bus which widens to 128-bits when interleaved, this computer requires 5-volt, 64-bit, 168-pin fast-paged mode (FPM) 70ns DIMMs that conform to the JEDEC MO-161 specification. This computer may also utilize JEDEC-standard 5-volt EDO DIMMs, but it must be stressed that its memory subsystem treats EDO like FPM, and no performance benefit accrues. This computer typically ships with 32MB of RAM (either a single 32MB DIMM in slot B4 or a pair of 16MB DIMMs in slots A4 & B4).

Note: MacGurus recommends the use of 168-pin, 5v EDO 64-bit, 2k refresh, 60ns DIMMs in this machine. EDO DIMMs are engineered to higher tolerances, and are more compatible with G3 processor upgrades. The two types of RAM can be mixed in a machine.

As there is no DRAM soldered to the logic board, the 7300-series requires that at least one DIMM be installed for the computer to boot. DIMMs may be installed in any slot, in any order, although a performance boost of 8-15% results from installing matching pairs of high-quality DIMMs in pairs, in corresponding slots (A4-B4, A3-B3, A2-B2, A1-B1), as a consequence of interleaving. The maximum amount of usable memory is 1024MB, in the form of eight (8) 128MB DIMMs.

Like other Power Macs of its generation, the 7300-series does not require DIMMs to be installed in pairs. In contrast to the 7200-series, however, the 7300's HammerHead ASIC memory controller does support memory interleaving, utilizing a 128-bit memory path. When purchasing memory for this computer, consequently, it is best to purchase DIMMs in matching pairs, to ensure that chipsets, densities and speeds all correspond. Disparate pieces may interleave, especially if they are of high quality and well within Apple specifications, but chances are enhanced if differences between DIMMs are minimized.

It must be stressed that the 7300-series in particular requires L2 cache DIMMs which are engineered to more exacting specifications than those acceptable in other Power Macs. Specifically, with processor bus speeds of 48MHz, 45MHz & 50MHz corresponding to faster processor speeds of 166MHz, 180MHz & 200MHz, superior parts must be used in the case of all ASICs and other subcomponents. When purchasing L2 cache for the 7300-series, whether from MacGurus or another vendor, it is advisable to emphasize that the cache is destined for use in the 7300-series, so that the vendor can ensure that the L2 is certified to work on this motherboard.

Specifications:
Logic Board RAM		None
Supported DIMMs		32MB, 64MB, 128MB.
Number DIMM Slots		Eight (8)
Supported VRAM		VRAM DIMM: 1024k
Number VRAM Slots		Four (4)
L2 Cache Supported?		L2 DIMM: 256k, 512k, 1MB
DIMM Type		168-pin, 5v EDO 64-bit, 2k refresh, 60ns

The 7300-series have four (4) 1MB VRAM DIMM slots on the logic board, and typically ship with two (2) slots filled. When two additional 1MB VRAM DIMMs are installed, the maximum capacity of 4MBs on-board VRAM is achieved.