[coreboot] BIOS Savior (RD1-PMC4/8X) unavailable? Build my own?
dave.frodin at se-eng.com
Fri Nov 9 19:51:58 CET 2012
My comments are inline below.
----- Original Message -----
> From: "Milo Hoffmann" <lineage2005 at gmail.com>
> To: coreboot at coreboot.org
> Sent: Thursday, November 8, 2012 11:29:41 PM
> Subject: [coreboot] BIOS Savior (RD1-PMC4/8X) unavailable? Build my own?
> Hello list,
> I might be missing something here, but I've spent all day trying to
> find a vendor (anywhere) who actually carries the BIOS Savior model
> I've determined I need. I did find on the ioss website that they have
> stopped manufacturing (I believe that's what they were trying to say)
> the models I need. 
> I have a PLCC32 socket (holding an SST 49LF004B) and the ioss
> reference page  indicates an RD1-PMC4 or RD1-8X (not 8X2).
> So... I started down the line of thought that I should be able to
> build my own, or come close enough to it with a switchable solution,
> for testing.
> Digging around, I found the wiki page indicating that it was possible
> to build your own . There was no PLCC example, so I searched a bit
> more and found this  thread and this  reference. The thread
> included a quick and dirty explanation of setup (provided that you
> have identical chips) along with other useful hints. The reference
> was less helpful unless I can get a 8Mb (1MB) flash chip that is
> otherwise identical to the SST49LF004B.
> But, the thread also said I would need a "32pin PLCC-Plugin-Adapter"
> for which I have found a few part numbers but no US distributor
> (haven't looked international yet).
> I have the datasheet for the SST49LF004B (and two known working
> but don't know the rest of the equation.
> The datasheet does not include the /CE pin from the quick and dirty
> explanation. I interpret it to mean the WE# (Write Enable) pin but am
> seeking confirmation from more informed folks.
> Can anyone on the list confirm I could hook up two identical
> SST49LF004B, using the WE# pin, to a three wire switch and have a
> functioning switchable BIOS?
If you are switching between two flash devices you would want to be
switching between the two CE# signals. Switching between the two WE#
signals would only disable writing to one device, and reads would be
sourced by both devices. You would need a separate pullup on each
devices CE# signal so that when that devices CE# isn't being driven
by the mother-boards CE# output that device would be disabled.
The devices don't necessarily need to be the same exact device, unless
there is some other constraint (e.g. size, flash support,etc).
You could have a SST49LF004B in one socket and a SST49LF002 or SST49LF008
in the other socket. They wouldn't necessarily even need to be the same
brand. They would both need to be FWH flash devices though. Most chipsets
have a strap that determines whether the ROM R/W cycles will go out on
the LPC bus as FWH or LPC-memory cycles.
> Is the more elegant solution to also find a PLCC Plug (like say,
> Winslow Adaptics W9302), two PLCC sockets and some board with which
> stick them all together?
> I would really like to return the 'spare' SST49LF004B back to it's
> board once I have a working coreboot firmware load. (I'm sure I'll be
> asking questions about that soon too. Still trying to get a QEMU
> coreboot working... hehehee...)
> Thanks for any response.
>  http://www.ioss.com.tw/eg/orderform0703.html
>  http://www.coreboot.org/Developer_Manual/Tools/Dual_Flash
> [EPIA flash questions]
> [Homemade BIOS switch for EPIA boards (and others with 2MBit chips)]
> coreboot mailing list: coreboot at coreboot.org
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