User manual

Etherboot User Manual

7. Making an Etherboot EPROM or EEPROM

Assuming you have satisfactorily set up your server environment, you may now wish to put the

Etherboot onto an EPROM or EEPROM. Naturally this assumes access to hardware to program (and

possibly erase) EPROMs. Access to a friendly electronics engineer and/or lab is one way to program and

erase EPROMs. Otherwise you can look at the commercial links page

(http://www.etherboot.org/clinks.html) for places you can buy programmed EPROMs from.

Some high-end network cards, for example the 3Com 905B, have a socket for an EEPROM which can be

programmed in situ with the right utilities. See any release notes accompanying Etherboot for more

information.

7.1. Choosing the EPROM

Most network cards come with a blank (E)EPROM socket even though it is seldom used. When it is

used, it is typically ﬁlled with a proprietary EPROM from the network card manufacturer. You can put an

Etherboot EPROM there instead.

7.2. Enabling the EPROM

First you must discover how to enable the EPROM socket on your card. Typically the EPROM is not

enabled from the factory and a jumper or a software conﬁguration program is used to enable it.

7.3. Size and speed of the EPROM

Secondly, you must discover what size and speed of EPROM is needed. This can be difﬁcult as network

card manufacturers often neglect to provide this information.

The smallest EPROM that is accepted by network cards is an 8k EPROM (2764). 16kB (27128), 32kB

(27256), 64kB (27512) or even 128kB (27010) EPROMs are possible. (You will often see a C after the

27, e.g. 27C256. This indicates a CMOS EPROM, which is equivalent to the non-C version and is a good

thing because of lower power consumption.) You want to use the smallest EPROM you can so that you

don’t take up more of the upper memory area than needed as other extensions BIOSes may need the

space. However you also want to get a good price for the EPROM. Currently the 32kB and 64kB

EPROMs (27256 and 27512) seem to be the cheapest per unit. Smaller EPROMs appear to be more

expensive because they are out of mainstream production.

If you cannot ﬁnd out from the documentation what capacity of EPROM your card takes, for ISA NICs

only, you could do it by trial and error. (PCI NICs do not enable the EPROM until the BIOS tells the NIC

to.) Take a ROM with some data on it (say a character generator ROM) and plug it into the socket. Be

careful not to use an extension BIOS for this test because it may be detected and activated and prevent

you from booting your computer. Using the debug program under DOS, dump various regions of the

memory space. Say you discover that you can see the data in a memory window from CC00:0 to

CC00:3FFF (= 4000 hex = 16384 decimal locations). This indicates that a 16kB EPROM is needed.

However if you see an alias in parts of the memory space, say the region from CC00:0 to CC00:1FFF is

duplicated in CC00:2000 to CC00:3FFF, then you have put an 8kB EPROM into a 16kB slot and you

need to try a larger EPROM.