ZM6 Features

Features
CPU Form Factor	Socket-370
Motherboard Form Factor	ATX
Chipset	Intel 440ZX
Memory	Three 168-pin DIMM sockets, 4 banks
Expansion	5 PCI slots (4 master, 1 slave)
BIOS	Award 2MB Flash BIOS
I/O	PS/2 Keyboard/Mouse, 2 USB, 2 serial, 1 parallel; 2 UDMA/33; 1 floppy
Headers	SB-Link, Wake-on-lan, IrDA; 10,000K thermistor
Bus speeds supported	66, 75, 83, 105,110, 112, 115, 120, 124, 133
Clock multipliers supported	2x to 8x in .5x increments
Hardware monitoring	Winbond

More Memory

Despite its low-cost nature, there's a lot to cover on this motherboard! The most notable is how it breaks with tradition. The 440ZX chipset supports up to 256MB of RAM on four memory banks. A standard DIMM socket allows for two banks, one for each side of the DIMM. A one-sided DIMM takes up one bank, while a two-sided DIMM takes up two banks. From this configuration, you can see that it's possible to support 256MB by using two 128MB double-sided DIMMS (thus filling up all 4 banks).

Now it's not possible to up the maximum memory allocation of the chipset, but Abit did pull a stunt by splitting the 3rd and 4th memory bank between two DIMM sockets. What does this mean? Well, you still have 4 banks and the 256MB limit, but Abit's been able to implement this through 3 DIMM sockets. This means that you'll be able to use three DIMMS as long as their bank usage adds up to 4 banks, as sockets 2 and 3 share banks 3 and 4. This means you can have two double-sided DIMMs in slots 1 and 2, or 1 double-sided DIMM in slot 1 and 2 single-sided DIMMs in slots 2 and 3.

It's certainly a little confusing, but it's a little easier to think in these terms. 32MB and 128MB DIMMs are double sided (and thus take up two banks), while 16 and 64MB DIMMs are single-sided. So if you have 2 64MB DIMMs, you can populate slots 2 and 3, and still be able to add a single or double-sided DIMM to slot 1 - if you decide to buy a 128MB DIMM, you can hit the 256MB limit even though you're using 3 DIMMs instead of 2.

More PCI Slots

Abit was also able to pull something similar with the PCI implementation on the ZX, which supports only 4 PCI slots. By piggybacking a PCI slave onto slot 4, Abit was able to implement 5 PCI slots onto the ZM6, another first for the ZX. It's important to note that like the DIMM modifications, there are a few complications to work out.

Since PCI5 (shared with ISA1) is a slave, it cannot bus master, making it useless for many video, network, or disk controller cards. However, for those of us with non-bus master peripherals such as 3D add-on cards (cough*voodoo2*cough) or certain PCI sound cards, the extra slot can be implemented without any loss of functionality.

While these modifications not only require compromise, but also an understanding of the exceptions involved, they do give end-users more choices and more options, something of paramount importance in the aftermarket, and serve to differentiate the ZM6 from the rest of the pack.