Jules_nerd wrote on 2026-07-24, 18:00:

Ahh just for ref for other UK buyers.. that tindie store looks a good few £ cheaper than where I bought! oh well!

Yes but Aliexpress generally prepays VAT and import fees for you and generally uses a slightly more reliable delivery... YMMV though.

Yoghoo wrote on 2026-07-24, 21:23:

Anyone has any experience with 4PX shipping? Curious how long it will take to ship to Europe.

1-2 weeks , but you'll have to deal with your local post office for import duties.

Yeah on Aliexpress for UK delivery it seems the published price included VAT, but then when I came to checkout it knocked it off.. bit odd...
So Im expecting to have to pay when it gets delivered...

Ive just had a message back from the Aliexpress store where I bought, the engineers reply when I asked about adding more DRAM on the 387 PCB was "387sx 33-40 MHz is fine. You can't install DRAM, 16M is already enough"
Its hard to get answers with translation and three people in the chain. Im not sure why you cant add more ram, it could be any or all of the following:
1. that he doesn't realize I can solder chips onto PCBs
2. The memory size is fixed in BIOS and it doesn't use the usual memory size detection routines...
3. The PCB design has an error...
4. I'm not sure exactly how this M6117 386SX actually manages to address more than 16MByte of ram, it certainly can, its in the datasheet (there is prob enough detail to work out how it does this.. but its lost on me right now). Maybe this isn't implemented correctly in the book386?
Who knows!!!
Ive asked again as Id like to try Read hat 5.2 again - on the pocket 386 it was horrendous! But then the only real system requirements stated in the manual is >16MByte ram...
and whilst I think 16MB should aid Win95 considerably, 32Mb would be better still I think...

Jules_nerd wrote on 2026-07-25, 14:15:

Ive just had a message back from the Aliexpress store where I bought, the engineers reply when I asked about adding more DRAM on […]
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Ive just had a message back from the Aliexpress store where I bought, the engineers reply when I asked about adding more DRAM on the 387 PCB was "387sx 33-40 MHz is fine. You can't install DRAM, 16M is already enough"
Its hard to get answers with translation and three people in the chain. Im not sure why you cant add more ram, it could be any or all of the following:
1. that he doesn't realize I can solder chips onto PCBs
2. The memory size is fixed in BIOS and it doesn't use the usual memory size detection routines...
3. The PCB design has an error...
4. I'm not sure exactly how this M6117 386SX actually manages to address more than 16MByte of ram, it certainly can, its in the datasheet (there is prob enough detail to work out how it does this.. but its lost on me right now). Maybe this isn't implemented correctly in the book386?
Who knows!!!
Ive asked again as Id like to try Read hat 5.2 again - on the pocket 386 it was horrendous! But then the only real system requirements stated in the manual is >16MByte ram...
and whilst I think 16MB should aid Win95 considerably, 32Mb would be better still I think...

The manufacturer is correct, that 386SX computer can only host a maximum of 16MB of system memory.

While the 386 CPU core can address 4GB of RAM, the chip package of the 386SX only has 24 address lines limiting the maximum directly addressable memory to 16MB (in order to use the 286 architecture that has the same memory bus).

You would need to design a new chipset and memory subsystem (essentially an entirely new type of computer) to have a 386SX page memory into and out of the first 16MB if you intended to use more than the directly addressable limit. Interesting, but never implemented to my knowledge since the original i386 and later 386DX could address much more memory at the time.

Jules_nerd wrote on 2026-07-25, 14:15:

Ive just had a message back from the Aliexpress store where I bought, the engineers reply when I asked about adding more DRAM on the 387 PCB was "387sx 33-40 MHz is fine. You can't install DRAM, 16M is already enough"

Yes, typical communication style 😀 While I understand the "why could you possibly want it?"-style replies, I find those a bit ironical considering he's selling a 386 in the 21st century...

Jules_nerd wrote on 2026-07-25, 14:15:

Ive asked again as Id like to try Read hat 5.2 again - on the pocket 386 it was horrendous! But then the only real system requirements stated in the manual is >16MByte ram...
and whilst I think 16MB should aid Win95 considerably, 32Mb would be better still I think...

I really do not think this is going to make as much improvement as you think. For some playthings like NT's or say Linux with X it is basically necessary, but the problem here is the CPU, and the overclock makes a difference but not that much.

fosterwj03 wrote on 2026-07-25, 15:16:

The manufacturer is correct, that 386SX computer can only host a maximum of 16MB of system memory.

I confused the SoC model, ignore me. But as jules_nerd mentions above, datasheet seems to point out to being able to address 64MB https://www.dmp.com.tw/app/webcamera/pdf/m6117d.pdf
There is some mention of banking in the memory controller, or maybe it is simply not accessible to the 386, but only to the other cores.

Even if a 286 or 386SX memory controller could page into installed memory beyond the 16MB limit, you would need software that supported the feature. I doubt DOS or Windows supported such a feature out of the box since it would not have been needed for a 386DX processor (and newer than 486 processors) and 286/386SX systems typically shipped with much more modest total memory. You might find code like that in specialized control systems that used SoC implementations of the 386SX, but probably not in retail software.

On the other hand, breaking the 4GB limit was a very real problem in more modern systems, thus PAE mode for computers with more than 4GB of memory. Again, that wasn't an issue in the 386's heyday.

Well I get why loads of people are saying things along the lines of 'It's a 386, its not going to run win95 well whatever you do'. Back in the day when Win95 came out i had a 386DX20 with 387DX 8MB ram kicking about and I didn't entertain even the idea of even trying win95 on it!

But with the pocket386, using the early floppy install version of win95 & no USB real mode driver loaded, I found it perfectly usable, provided I didn't use any (or too many) applications that needed more than the few MB or so that was free after the OS loaded...so the 8MB is rather limiting/tight.
So I think its reasonable for me to say with 16MB ram that it I will find it usable.. OK it may not meet others expectations of how fast it should run, but for me, personally, I expect it to be OK.
I think others reports of it being too slow when they tried it could be that they have higher threshold for what they consider to be OK, or maybe they are using a later version of win95; from what I can gather pretty much all later versions have a higher memory footprint and then 8MB really just isn't enough and Id expect ti to pretty much grind to a halt.

Why is it that I find it OK , when I prob wouldn't on other 386s back in the day???, perhaps its the compact flash, perhaps its that its running EDIT (interleave is not enabled when using EDO) 50nS EDO RAM, both of which will help offset that its just a 386sx... OK its never going to be anywhere near a 486... and i haven't tried any seriously processor intensive applications...
But just a bit of everyday use I think will be ok, based on my exp with the pocket 386....
As for Redhat 5.2... well on the pocket386 it was usable at the command prompt, but noticeably slow.... It was totally unusable running X. As it was slow at the command prompt Im not sure the extra memory will be enough to make X usable, but I'll happily give it a go to find out...

fosterwj03 wrote on 2026-07-25, 16:37:

Even if a 286 or 386SX memory controller could page into installed memory beyond the 16MB limit, you would need software that supported the feature. I doubt DOS or Windows supported such a feature out of the box since it would not have been needed for a 386DX processor (and newer than 486 processors) and 286/386SX systems typically shipped with much more modest total memory. You might find code like that in specialized control systems that used SoC implementations of the 386SX, but probably not in retail software.

On the other hand, breaking the 4GB limit was a very real problem in more modern systems, thus PAE mode for computers with more than 4GB of memory. Again, that wasn't an issue in the 386's heyday.

Yeah I just dont know enough about the banking system thats used, maybe it needs BIOS support?
But I think you may well be right, it may well be addressable, but if the software 'thinks' its a regular 386sx it may not even try... that may well be why I got the answer back that it cant be done...
Yeah, IIRC many of the PC104 systems based on the M6117 claim to be able to use more than 16MB, but of course who knows what software they were running.

fosterwj03 wrote on 2026-07-25, 16:37:

Even if a 286 or 386SX memory controller could page into installed memory beyond the 16MB limit, you would need software that supported the feature. I doubt DOS or Windows supported such a feature out of the box since it would not have been needed for a 386DX processor

You only need support for this paging from the OS, this is a 386 and there is protected mode after all, and it's not like we haven't already done hacks for using PAE or even long mode to have 9x use ungodly amounts of RAM (as a ram drive though since 9x has other limitations).

In any case , this is just speculative, most likely the 386sx can't access anything other than 16MB and the datasheet just glosses over that (the first page is already written in a way that seems to hint as much).

Just looking for fun projects that can be done in a short time. 😀

I am already annoyed that the touchpad is most likely abstracted in some way so that it looks like a serial MS Mouse, which means most likely no way to do two finger scrolling.

The trackpad does look rather recessed in the case as well... time will tell... I guess the case will be 3D printed too?
At least there wont be an awkward dongle/adapter hanging out of the back when you want to use a mouse!

Ive jsut been scanning through the datasheet and come across another feature that might be of use in solving the pocket386s BIOS reset - but Im not sure, its out of my area of knowledge...
I solved the issue by adding on a power supply monitor chip to give a PWG power good signal to the M6117, just as suggested in the datasheet.
However on p15 of the datasheet top right it says
"The switching power supply sends a PWG (power good
signal) to M6117D to generate system reset signals, like
RSTDRV, RESETL, and resets the chip to initial state.
Also the reset signal can be generated by internal
emulation RC reset and shutdown cycle"

Could this somehow be set to keep everything in reset longer on power on?
Im not sure I get what its saying...

Again outside of my area of knowledge, but do the memory auto sizing routines that start on P58, section 5.3 give clues on how it is managing to access more than 16MByte RAM?

Jules_nerd wrote on 2026-07-25, 16:49:

Well I get why loads of people are saying things along the lines of 'It's a 386, its not going to run win95 well whatever you do […]
Show full quote

Well I get why loads of people are saying things along the lines of 'It's a 386, its not going to run win95 well whatever you do'. Back in the day when Win95 came out i had a 386DX20 with 387DX 8MB ram kicking about and I didn't entertain even the idea of even trying win95 on it!

But with the pocket386, using the early floppy install version of win95 & no USB real mode driver loaded, I found it perfectly usable, provided I didn't use any (or too many) applications that needed more than the few MB or so that was free after the OS loaded...so the 8MB is rather limiting/tight.
So I think its reasonable for me to say with 16MB ram that it I will find it usable.. OK it may not meet others expectations of how fast it should run, but for me, personally, I expect it to be OK.
I think others reports of it being too slow when they tried it could be that they have higher threshold for what they consider to be OK, or maybe they are using a later version of win95; from what I can gather pretty much all later versions have a higher memory footprint and then 8MB really just isn't enough and Id expect ti to pretty much grind to a halt.

Why is it that I find it OK , when I prob wouldn't on other 386s back in the day???, perhaps its the compact flash, perhaps its that its running EDIT (interleave is not enabled when using EDO) 50nS EDO RAM, both of which will help offset that its just a 386sx... OK its never going to be anywhere near a 486... and i haven't tried any seriously processor intensive applications...
But just a bit of everyday use I think will be ok, based on my exp with the pocket 386....
As for Redhat 5.2... well on the pocket386 it was usable at the command prompt, but noticeably slow.... It was totally unusable running X. As it was slow at the command prompt Im not sure the extra memory will be enough to make X usable, but I'll happily give it a go to find out...

Flash storage offers a lot of performance for old interfaces. IDE PIO modes are essentially maxed-out with a cheap CF card.

Jules_nerd wrote on 2026-07-25, 18:12:

Again outside of my area of knowledge, but do the memory auto sizing routines that start on P58, section 5.3 give clues on how it is managing to access more than 16MByte RAM?

The MA11 line gives access to the 64MB of RAM. 4x 16MB SIMMS.

Normally only Apple computers used the MA11 line with 30 pin SIMMS, but this chipset can too. Whether or not the Book/Pocket 386 uses it or not is another question.

I think many of the PC104 products with the M6117 use 72pin SIMM, often a couple of the same 2MByte chips that the pocket386 has & one 72pin simm socket.
I can certainly look at the PCBs to see how many address lines are connected. But the part I don't get though isn't that side of the memory controller, its the 'other side', its how the 386 address lines are connected to the memory controller? It must deviate from a standard 386sx somehow, I guess there are really only 2 basic ways it can address more memory, either internally it has a couple more address lines than a standard 386sx, or it has some kind of special register somewhere that selects a different address range...
Mind you, as as been said, its speculation & I suppose its prob not likely to lead anywhere... So I should prob drop this one!

After Ive been looking around for an 80387.. 40MHz ones are really thin on the ground & pricey... 25MHz ones seem much more common & a bit more reasonable..
25MHz is just within allowable asynchronous range for running an Intel 80387 with a standard Intel 80386.. I wonder if the designers of the M6117 kept the interface with the 80387 100% the same as the intel?... If so it should be possible to mod it by adding a 25MHz clock. If only that m6117 datasheet was more complete!

RAM is addressed in 12 bit rows and 12 bit columns (24 bit) from the CPU, but for some reason it makes 32MB per bank for RAM, but only 16MB for the ISA bus at the same 24bit addressing.... I think it's counted differently.

A 16-bit write to the ISA bus may be two 8-bit writes. Where a 16-bit write to RAM is one 16-bit write (16-bits is the minimum word size). Not sure if that's right.

I'm not sure where this is heading now, but sometime ago I did look at the possibility of adding more RAM to the pocket386, so I did look at the addressing of the DRAM, Im no expert on this so I wont be surprised if there is an error in the following, but at least I thought Id offer what I have rather than keep saying its beyond me...
I came to the conclusion that its really not easyto upgrade the RAM on teh pocket 386, prob the best option would be to remove some, or all the DRAM and graft on a 72 pin simm socket. Clearly this isnt trivial! and rather error prone....
The 386sx has a 16bit data bus, so the memory is arranged in 2x Byte wide banks .
How the memory is arranged is one limitation, but also the allowable configurations in the table of the M6117 manual Page 15 puts further limitations on what you can do.
At the moment you have MODE17 as defined in the table, 4 banks of 1M x 2 bytes. 1 DRAM chip is used for each bank.
You cant just double every bank because the table doesnt have an entry for 4 banks of 2M x 2 bytes...
If you want a total of 16MByte, the only option is MODE21, 2 banks of 4Mx2Bytes (- rather surprisingly leaving 2 banks empty....)
(the memory arrangement in the published book 386 schematics doesn't appear to make sense, the CAS/RAS lines dont appear to be connected & its got 256K x 4bit DRAMs??)
my GUESS (we'd need better schematics or to reverse engineer the PCB to be sure) is that on the Book 386 the designer has put 2 banks of 4Mx2Bytes on the main PCB (MODE21) and another two banks of 4Mx2Bytes on the 80387 PCB, MODE30 - but it seems this isnt usable!
on the Pocket 386 the address connections to each DRAM chip from the M6117 are:
1. 12 address lines, MA0 to MA11 (common to all DRAM) are all on the schematic, however I believe in the 2Mx2Byte DRAM chips used MA10 & MA11 (pins 19 &20) are not connected, so only 10 address lines are in use, but the address lines are there to address more memory...
2. Each chip has its own, seperate RAS & two CAS s
The two CAS lines are used to select the high or low byte in each DRAM - they can operate in byte wide or 16bit word modes, depending on the use of these i.e you drive both together for 16 bit wide mode. So at least in theory, the connections are there to allow byte wide access, but I'm not sure if this is used... (IF the chips are in a system that has a byte wide data bus you connect the low and high byte data lines together, they are tristate, enabled by the corresponding CAS line. )

So I think that the M6117 has the required address, RAS & CAS to address 64MByte- but this is the M6117's memory controller interface with the DRAM. The question is how the 386 inside the M6117 is connected to the memory controller to allow it to access this much... I think MA table on page 76 to 78 of the manual may well have a clue here, I get the MA is memory address - the address lines used externally to the DRAM. I guess the A* in the table are the 386s address lines??? But they only seem to go from A1 to A16, the PA entries from PA17 to PA25? Are the A8 and PA* all part of the same address bus??? I dont know!

In the mean time my 386DX/40 desktop only has 8MB memory and that is more than I ever need on that pc. 😜 16MB is really overkill for what I will be doing on this laptop.

Did anybody already see the external ISA board for the Book386? Seems it also supports 16 bit cards?

No, i spotted the connectors on the back of the Book 386, but not the adapter... do you have a link?

Jules_nerd wrote on Today, 19:14:

No, i spotted the connectors on the back of the Book 386, but not the adapter... do you have a link?

No I didn't but the photo on the back shows it needs 2 cables. I guess you need only 1 for 8 bit?

My order status is still: Your package is waiting to be picked up by the carrier. So will take a couple of weeks until it arrives I guess.