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nar001 Page Icon Posted 2021-12-29 12:07 PM
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Hello! So I'm new to the whole WinCE/Handheld PC stuff and I was curious, I've been looking around and seen that many people tried to put Linux on these things, but they always have to be booted from WinCE itself, why is that? I guess I'm just curious why you can't just replace WinCE itself, so it would boot to linux? Thanks for the help!
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C:Amie Page Icon Posted 2021-12-29 12:29 PM
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Hello nar001, welcome to the site.

It is because the hp 300 - 800 series had single write ROM chips with no J-TAG procedure (a way to talk to the chip's controller externally/in software without de-soldering it). If you're not techie then think of it like booting your computer from a CD-ROM. It can only ever boot what it was initially burned to boot with. You can't erase it and start again.

It is technically possible to de-solder the ROM chips and replace them - even replace them with flash ones. However documentation for the boot loader is scarce and to my knowledge in the absence of a software or hardware J-TAG procedure, re-programming them requires a de-solder, reprogram and a re-solder. I.e. very time consuming, complicated and moderately high risk.
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nar001 Page Icon Posted 2021-12-29 1:39 PM
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That makes sense! Tho I'm surprised nobody tried to desolder the rom chip and such, did anyone try to update WinCE at least? I don't really know how it works drivers wise, I assume it's a lot more customized than normal Windows?
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joval Page Icon Posted 2021-12-29 2:31 PM
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Good summary/explanation of the challenges the J720 poses regarding ROM updating, etc.

Yes, booting into Devuan Linux by way of WinCE is a bit "clunky"... and no true sleep mode runs the battery down after a few hours. But Linux X-forwarding opens the door to the internet once again for the J720... and much more.

It won't ever replace your tablet or laptop, but it's great for posting emails and blogs like this, IMO, especially if set in it's docking station charging when not in use.

joval (and his J720/Devuan/Raspi sidekick)

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C:Amie Page Icon Posted 2021-12-29 3:38 PM
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nar001 - 2021-12-29 1:39 PM

That makes sense! Tho I'm surprised nobody tried to desolder the rom chip and such, did anyone try to update WinCE at least? I don't really know how it works drivers wise, I assume it's a lot more customized than normal Windows?
They have, it's just difficult to do. The other issue is that the 720 (say) has a 32MB ROM. Modern Linux Distro's are multiple GB's in size. There is really a practical limit over how much chip-stuffing you can do. The only reasonable thing that could be done would be either CE .net (not much of a leap forward) or to write some middleware bootloader that hands-off to a CF card to perform the rest of the legwork.

If you are interested in getting involved and helping to do that, have a read of the Linux on the Jornada 720 - Status thread
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nar001 Page Icon Posted 2021-12-29 4:56 PM
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That does sound interesting! I'll have to check stuff out then

And C:Amie Thanks for your answers, I'm sure it's something lots of people asked before so it's appreciated! I've always kinda seen these devices from afar so it's interesting to know they load everything in Ram! I guess it was a way to make it snappier? It's a shame they're cut down Windows though, but I guess it was complicated to fit it in a device like that in the early 2000s!
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C:Amie Page Icon Posted 2021-12-29 5:56 PM
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They don't load everything in RAM, they eXecute In Place (XIP) calls to the ROM. The user file system, system file system and system state is however entirely RAM based.
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nar001 Page Icon Posted 2021-12-29 7:08 PM
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Oh right, so when you load something it loads from the ROM but anything you change gets saved to RAM?
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C:Amie Page Icon Posted 2021-12-29 7:14 PM
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On most devices, yes. Not all CE devices are XIP. Most of the major consumer ones were however. The memory map for ROM and RAM are contiguous, so the system can call independently of the file system. CE has a file system mapper that handles conversion from file system calls to memory addresses.

Unless you have need to overwrite a system file, they'll just stream from ROM.
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nar001 Page Icon Posted 2021-12-29 7:31 PM
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That's pretty interesting, tho I wonder why they never thouhgt about ways to upgrade the WinCE version, even as a file to run and such? You said people did try, are there any threads about it? I'm curious if it's possible at all at least, and is CE .NET not anything different than WinCE3? (I'm also bookmarking that linux one, since it does also seem pretty cool!)
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C:Amie Page Icon Posted 2021-12-29 7:58 PM
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If you wanted to upgrade a CE device prior to about the end of 2001, you physically replaced the ROM chip. Putting 32MB+ of flash ROM on the devices just wasn't an extra expense that they wanted to couple to a device that was already £800+.
By the time CE4 arrived, they needed a 128MB ROM chip.

The flash ROM was largely the work of Kristoffer Ericson, although I think _dev-null has been looking at it.

Try
https://www.google.com/search?q=%22kristoffer%22+flash+ROM&#...

CE .net is more powerful than HPC2000, but does't come with Office, the sync stack or the consumer features. If you're going to upgrade it, you really want to go as high as possible... but given that CE is dead and has no viable route to modern browser technology. You really need both the RAM upgrade to 128/256, the ROM upgrade with multiple GB (which won't happen) and Linux.
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nar001 Page Icon Posted 2021-12-29 9:54 PM
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Yeah that makes sense, I hope the Linux port project will go well then, it really sounds like they're stretching what these devices can do! Tho I have to say it'd be pretty sweet to dual boot both WinCE for old games and all, and Linux for actual work! I'll have to check if any PCMCIA cards exist to go online, tho it sounds like a pain
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Rich Hawley Page Icon Posted 2021-12-29 9:57 PM
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And even if you could simply update the operating system by reflashing the rom chip to a newer version...you would still need to have the specific device drivers for the actual hardware to function. Since the bsp is unique for each handheld...that would be a whole another issue.
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nar001 Page Icon Posted 2021-12-29 10:09 PM
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Oh yeah I was mostly wondering if you couldn't like extract them from the WinCE rom or something, I really have no idea how they work, I'm really REALLY new to all of this hah. Tho it always kind of fascinated me, it's like that whole other totally new different branch of Windows, it's neat
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C:Amie Page Icon Posted 2021-12-29 10:42 PM
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See the HCL on this site for compatible hardware.

BSP's are a huge issue for rebuilding CE, not an issue for Linux mind. The truth is that the HAL on CE 3 wouldn't run on later releases anyway. It would require a full re-engineer probably.
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