Motherboard Specifications

My board has the following specifications:

Main System Logic

• VLSI Technology VAS96011/12 Golden Gate 2 PowerPC chipset
• Bus clock: 50-75 MHz, PCI clock: 25-37.5 MHz (synchronous)
• 512 KB Pipelined Burst Synchronous SRAM L2 cache (upgradable to 1 MB)
• Apple Hydra Mac I/O chip
• Winbond W83C553F PCI/ISA Bridge with enhanced IDE (Ultra/33)
• National Semiconductor NS87308VUL Super I/O controller
• Crystal CS4236B audio

Sockets and Connectors

• ZIF socket for a 603e or 604e PowerPC CPU (up to 333 MHz)
• 4 DIMM sockets for system memory, up to 768 MB FPM/EDO/BEDO RAM or 512 MB SDRAM (3.3V, unbuffered) [ why are there 4 DIMM sockets?? for a test probe?? ]
• 512KB L2 cache expansion (COAST compatible)
• MacOS ROM socket
• 4 32-bit 33 MHz PCI slots
• 1 16-bit ISA slot
• ATX power supply
• 50-pins header for SCSI-II
• External 50-pins SCSI-II connector
• 2 x 40-pins header for IDE
• 34-pins header for floppy
• PS/2 keyboard and mouse
• Apple Desktop Bus
• 2 x DB9 serial
• 2 x SCC serial
• DB25 parallel
• Audio in and out

• Bus clock: 60-83.5 MHz, PCI clock: 33 MHz (asynchronous)
• 1 MB Pipelined Burst Synchronous SRAM L2 cache (not upgradable)
• Only 3 DIMM sockets for system memory
• No ISA slot
• External Mac DB25 SCSI connector

Motherboard Connectors and Jumper Settings

Connectors

Jumper Settings

Warning: production boards have different jumpers for

• CPU voltage (JA2V)
• CPU clock divider (JCFG0/1/2/3)
• CPU operation mode setting (JPRMOD)
• host/PCI bus speed (JCLK)
• L2 cache (straps instead of jumpersi JTAG and JLPD)

Memory requirements for the LongTrail

DIMMs

DIMMs with 168 pins can contain 1 or 2 banks of memory. Usually single sided DIMMs have 1 bank of memory, while double sided DIMMs have 2 banks of memory, but this is not always the case.

DIMMs provide a 64 bit wide path to the memory. With 8 bit wide ICs (e.g. 2Mx8 or 8Mx8) each bank on the DIMM contains 8 ICs. With smaller (e.g. 4Mx4) or wider (e.g. 4Mx16) ICs, you need more or less ICs to fill each bank on the DIMM.

FPM, EDO and BEDO

SDRAM

The GG2 supports up to 512 MB of SDRAM in 4 banks (i.e. 2 DIMM sockets). The GG2 supports SDRAM with 2 internal banks only. If you have SDRAM with 4 internal banks, you can use half the amount of memory only, or none at all if you have back luck!

SDRAM ICs

The internal SDRAM banks are used to implement on-chip memory interleaving and are the reason for the higher performance that can be achieved with SDRAM, compared to older memory technologies. Read more about SDRAM in this announcement from IBM from 1996.

Later SDRAM could have 2 or 4 internal banks (IBM and HP). To support this, an extra bank select line BA1 was added in addition to BA0. Since the GG2 is a design from 1996 or before, it makes sense to assume it holded pace with the memory technology from that moment. Hence the GG2 does not support the BA1 bank select line. The memory controller in the Motorola MPC106 `Grackle' chipset (used in the Apple PowerMac G3) does support SDRAM with 4 internal banks, starting with revision 4.0 of the MPC106. AFAIK all PC chipsets that support SDRAM do support SDRAM with both 2 or 4 internal banks.

Most 16 Mb SDRAM ICs have 2 internal banks. 64 Mb ICs are available from the major DRAM manufacturers with both 2 or 4 internal banks. Since this is a PC centered world, 64 Mb ICs with 4 internal banks are most popular.

SDRAM DIMMs

• 16 MB and 32 MB DIMMs are usually composed of 16 Mbit (2Mx8) ICs (8 or 16 ICs per DIMM, i.e. 1 or 2 DIMM banks), so most of them will work. However, these days 16 Mbit ICs are being phased out in favor of the higher density 64 Mbit technology. New 32 MB DIMMs are composed of 4 64 Mbit (4Mx16) ICs, in 1 bank.
• 64 MB and 128 MB DIMMs are usually composed of 64 Mbit (8Mx8) ICs (8 or 16 ICs per DIMM, i.e. 1 or 2 DIMM banks). An alternative composition for 64 MB DIMMs has 8 64 Mbit (4Mx16) ICs in 2 banks. I haven't found any 64 MB or 128 MB DIMMs yet that are composed of 64 Mbit ICs with 2 internal banks. They do exist according to the webpages of the manufacturers.

  Older 64 MB DIMMs use 16 Mbit technology and are composed of 32 16 MBit (4Mx4) ICs, forming 2 banks of 32 MB (16 ICs). These will work if the 16 MBit ICs have 2 internal banks.

• 256 MB DIMMs are probably composed of 32 64 Mbit (16Mx4) ICs in 2 DIMM banks. When 64 Mbit will be phased out by 256 Mbit technology, 256 MB DIMMs will be composed of 8 256 MBit (32Mx8) ICs.

Buying SDRAM DIMMs

Things will only get worse, because of the fastly evolving memory technology and computer world. Older technology is being phased out, and you can't expect to keep on buying memory for such old machines (sigh).

You can verify whether the type of your memory at the website of the memory manufacturer. Useful links:

• Fujitsu Microelectronics Memory Products
• Hyundai Electronics Semiconductor
• IBM Microelectronics Memory Products
• LG Semicon Synchronous DRAM
• Micron Semiconductor
• Samsung Semiconductor
• Siemens Memory Components and Modules
• Texas Instruments Memory
• Toshiba

Memory types I have used

• 32 MB EDO DIMM, composed of 8 16 Mbit (2Mx8) ICs
• 32 MB SDRAM DIMM, composed of 8 16 Mbit (2Mx8) ICs
• 64 MB SDRAM DIMM, composed of 32 16 Mbit (4Mx4) ICs

• 64 MB SDRAM DIMM, composed of 8 64 MBit (8Mx8) ICs in 1 bank: 32 MB usable
• 64 MB SDRAM DIMM, composed of 8 64 MBit (4Mx16) ICs in 2 banks: unusable
• 128 MB SDRAM DIMM, composed of 16 64 Mbit (8Mx8) ICs in 2 banks: 64 MB usable