ARM5 (?) - PXA255

[David Witten]

Thanks for the reply.  Yes, the link you provide points to the support 
site for the boards I'm referring to.

This is sort of what I expected.  I was unclear whether the efforts to 
port to ARM architectures supported non-MMU systems.  I gather that they 
do not.  I don't entirely understand how difficult it is to separate out 
the memory management strategy from the rest of the OS.  I imagine that 
it is no simple undertaking.

I have looked at uCLinux and uCos for those situations, but I'm not 
really certain that the ARM7 projects that interest me have real need of 
a full blown OS anyway.  I suspect that a light weight real time 
executive is probably the most that is really necessary.

If the box that you are putting together is based on or similar to the 
Gumstix designs, I know that sshd works well and is active by default on 
their standard boards.

I have m0n0BSD running on a number of WRAP and Soekris boards, which use 
a Pentium 5 class AMD GEODE SC110 and I use these days as Firewall/IPSEC 
VPN endpoints with very satisfactory performance at 266 MHz.  I don't 
believe that crypto is likely to be a problem on anything 200 MHz or above.

Unfortunately, though these are low power boards, they still do not 
offer the power management and the physical density that the XScale 
family does. And while they are rugged and I2C plus a few GPIO's are 
pinned out on the boards, they don't provide the rich set of I/O 
facilities one could want.

M. Warner Losh wrote:
> In message: <43D0607F.3000404 at wwrinc.com>
>             David Witten <wittend at wwrinc.com> writes:
> : For what it is worth, I would really like to be able to run FreeBSD on 
> : the Gumstix boards.
> 
> Assuming that you mean:
> 	http://www.gumstix.org/tikiwiki/tiki-index.php?page=gumstix
> 
> : In case someone's not familiar with them, they are PXA255 boards (at 
> : present) with 6 or 16 MB flash, 64Mb SRAM, a MMC Flash card socket, USB, 
> : I2C, SPI, and UARTS.  Very inexpensive add-ons for robotics, WiFi, 
> : ethernet and other good stuff are available as well.  Essentially a 200 
> : or 400MHz PDA on an 20mm x 80 mm board (like a stick of gum). The least 
> : expensive board is < $100 US.
> 
> 64MB is plenty of space to run FreeBSD.  The company I work for is
> looking at running in 64MB, and we're thinking it will be plenty for
> what we're looking at putting on the box (although sshd might be a bit
> ambitious for our chip).
> 
> 4MB flash will be enough for a kernel, but might not be enough for
> both a kernel and a ram disk.  At least not without a lot of
> subsetting work.  We're going to do some, but not likely to the level
> of busybox.  Busybox might also be a good alternative, but since it is
> GPL'd, our company prefers not to use it...
> 
> You'll need drivers for I2C, SPI and MMC controller.  I'm working on a
> mmc stack for the board we're using, but the MMC bridge part might
> have a different interface and need its own driver.
> 
> This is a doable project.
> 
> : I would also really like to have an ARM7 port, probably something that 
> : could run on the Olimex LPC-H2294 board ($99 US) that has 16k + 1Mb SRAM 
> :   and 256k + 4Mb Flash.
> : 
> : Is either of these projects feasible, and is there anyone out there who 
> : has done work in either of these directions?
> 
> ARM7TDMI-S doesnt have a MMU.  You are going to have a tough time
> porting FreeBSD.  Such a small amount of ram/rom also is likely to be
> a problem.  While there are some ARM7 CPUswhich do have a MMU that
> FreeBSD could run on (like the Cirrus Logic EP7312), I don't think the
> Phillips LPC2294 is one of them.
> 
> Warner