Re: 3C905 and 27C512 (fwd)

[Charl Barnard <charl@up.ac.za>]

Hi Netbooters,

Just to let you know regarding Markus's message, and also correspondence
with Jose', who did the same thing, I got netboot running on a 3COM 3c905
with a 27C256 by just soldering a wire from pin 28 on the 27C256 to pin 32
of the socket, and aligning the chip in the socket as follows:


 Wire connecting pin 28 on EPROM to pin 32 on socket.
  -
 | |
|oo**************|
|  :             |
>  )   27C256    |
|  :             |
|oo**************| 

where o shows an unused pin on the socket, and * an EPROM pin plugged into
the socket.

So thanks a lot Markus for all the trouble you took to check up the data
sheets for me (I also had a look at the Atmel 29C512 ones and came to the
same conclusion), and thanks Jose for your answer.

Cheers,

-- Charl
=================================+=====================================
Charl J. Barnard                 |            NW II Building Room 5-1.3
charl@up.ac.za                   |            University of Pretoria
Tel.: +27-12-420-2444            |            Pretoria, South Africa
   "To understand recursion, one must first understand recursion."

---------- Forwarded message ----------
Date: Mon, 17 Nov 97 15:23:43 -0800
From: markus@infoscape.com
Reply-To: netboot@baghira.han.de
To: Charl Barnard <charl@up.ac.za>
Cc: netboot@baghira.han.de
Subject: Re: 3C905 and 27C512

Charl Barnard writes:
 > > I have used the 27C512, with only 28 pins!
 > > 
 > > Bye.
 > > Jose A. Martinez
 > 
 > My question: have you ever found out how he did it ? Did he build some
 > kind of adapter ? Is there some way to use the 28-pin chip directly in the
 > 32-pin socket ?

If you compare pin-outs for the 27c010
(http://www.amd.com/products/nvd/techdocs/10205f2.pdf) and the 27c512
(http://www.amd.com/products/nvd/techdocs/08140h.pdf) or even the
27c256 (http://www.amd.com/products/nvd/techdocs/08007h.pdf), you will 
realize that they are very similar. If you are lucky, you might just
get away with plugging a 27c512 or 27c256 into the 32 pin socket. It
all depends on whether pin 30 of the socket is connected to Vcc (+5V); 
if that is not the case, soldering a single wire to the connector
should fix your problem. You might have to software-configure your NIC 
afterwards.

N.B. I have not tested this myself, but looking at the manual page it
looks like very simple fix.


Markus

-- 
Markus Gutschke                         Internet: markus@infoscape.com
Infoscape, Inc                          Phone:    +1-415-537-3778
657 Mission Street, Suite 200
San Francisco, CA 94105                 main()
                                        {((void(*)())"\360\017\307\310")();}

Disclaimer: The above message represents my personal opinion; It does
            not constitute an offical statement by Infoscape!

PGP signature