The maximum RAM a 386SX can have is 16MB. 4MB was very common on 386SXs toward the end of their run. I only had 4MB in mine, and it ran most software without issue.

I tried Windows 95 once on my 386SX. While it did run, it wasn't a pleasant experience.

FYI, the first 1MB contains the lower memory region (640k) and shadows the BIOS. That leaves only 3MB for expanded/extended memory on your computer. That might explain your memory capacity error.

4MB of RAM should be fine for most applications.

The only game of that era I know that can use more is Links 386, which can take advantage of up to 8MB of RAM.

386sx cache is indeed rare because SX was supposed to be super cheap lowend, cache controller and SRAM were expensive. 8KB cache is usually integrated in late (>=1992) chipsets like Macronix, for example https://theretroweb.com/motherboards/s/tk-tk83305p9-4n-d-02

There is nothing that requires more than 4MB and would run well on SX so you are good there.

Well, if you wanted to run OS/2 2.1 or Warp on that system it WOULD benefint from more than 4MB RAM.

Only things I know of which would benefit for more than 4MB of RAM is Win 3.x and Links 386 Pro (recommended 8mb ram in the official specs), and Speedsys which you've already mentioned.

As you say you're a beginner, a tip about RAM on systems like these:

The 386SX has a 16b wide memory bus. 30p SIMMs are 8b wide. So you need to install them in pairs. As stated, the address bus was 24b wide, meaning max 16MB in total. Finally, your motherboard may require parity or not. If it requires parity; parity SIMMs have 3 or 9 chips, non-parity SIMMs have 2 or 8 chips. If parity is not required, parity SIMMs work too, just without the parity being utilized. 30p SIMMs come in 256kB, 1MB, 4MB and 16MB versions. As you cannot address >16MB and SIMMs need to be placed in pairs, don't use 16MB SIMMs.

WIthin these constraints, you can basically mix & match as you like. You currently have 4x 1MB. A logical upgrade would be to replace one pair with 4MB SIMMs giving 10MB total (or just remove all the 1MB SIMMs for use elsewhere, leaving you with 2x 4MB = 8MB). However you will only notice the benefit from this upgrade if you run heavy (windowing) software. If you don't run out of memory now, additional memory won't speed things up.

As for cache - yes, that's pretty unusual in combination with a 16b external CPU, but not unique. I have an Alaris Leopard board here with IBM 486SLC/2 on it (pretty much the fastest 16b external CPU out there) that also has some cache (and VLB slots - go figure 😜 ). I'm surprised you notice the faster speed so much, as it's still behind the same 16 bit bottleneck. Still, latencies are lower which helps. In any event, the proof of the pudding is in the eating and you benchmarked it yourself, so yes, keep it enabled and enjoy what benefit it gives.

dionb wrote on 2024-01-05, 14:56:

I have an Alaris Leopard board here with IBM 486SLC/2 on it (pretty much the fastest 16b external CPU out there) that also has some cache (and VLB slots - go figure 😜 )

Well that's certainly an interesting combination. I'm sure the vl bus still helps some since it's clocked much higher than ISA would be and bandwidth is bandwidth right (albeit half of what it should be)

DrAnthony wrote on 2024-01-05, 16:57:

dionb wrote on 2024-01-05, 14:56:

I have an Alaris Leopard board here with IBM 486SLC/2 on it (pretty much the fastest 16b external CPU out there) that also has some cache (and VLB slots - go figure 😜 )

Well that's certainly an interesting combination. I'm sure the vl bus still helps some since it's clocked much higher than ISA would be and bandwidth is bandwidth right (albeit half of what it should be)

Higher clock, lower latency (even despite the obligatory 2 16b CPU transfers per one 32b VLB transfer) and - not to be underestimated - no other ISA devices hogging the bus. It's definitely faster with VLB VGA and I/O than ISA, although slower than a 486 with 32b access to VLB.

dionb wrote on 2024-01-05, 18:23:

Higher clock, lower latency (even despite the obligatory 2 16b CPU transfers per one 32b VLB transfer) and - not to be underestimated - no other ISA devices hogging the bus. It's definitely faster with VLB VGA and I/O than ISA, although slower than a 486 with 32b access to VLB.

When you look at the VL Cirrus Logic 542x, none of them does 32 bit transfers to the VLB - they all are 16 bit only.

Lots of great information here thanks!

The overall consensus is that 4Mb is fine for DOS, and my modules have 9 chips so parity memory, though not sure if it is required. I didn't explain it before but this motherboard is actually a ISA card, it just goes into a straight backplane with power connections, so as far a motherboards go it is kind of small.
I do have some old win 3.1 floppies so someday I may decide to play around with that on this machine, in which case I will keep an eye out for larger modules.

Alex_03 wrote on 2024-01-06, 02:22:

The overall consensus is that 4Mb is fine for DOS [..]

Yup. Though SmartDrive's cache can do benefit from extra memory.
The real world maximum for the cache was around 4 MB, I suppose.
With the /double_buffer setting enabled (for Windows 3.x), a bit more even.

Of course, it depends on the configuration of the PC.
If it has a CF card and a floppy drive, SmartDrive isn't so important.
If a CD-ROM drive is installed, though, SmartDrive can make a difference.

It will read ahead and cache big chunks of data (not unusual for games/ talkie titles),
so the gameplay won't stutter and the drive won't "squeak" all the time because of head movement
(without a cache, every file needs to be re-read upon access).

Anyway, it's just a footnote, maybe.
I didn't use SmartDrive back in the 90s, when I had my 286 w/ 4MB of RAM.
The CD-ROM drive was a single-speed type (via PAS16 SCSI) and access was quite jerky, but I could live with it.

Also, a caching controller can do the same thing as SmartDrive, maybe. For HDDs/floppy drives, at least.

Edit: As a workaround, a modern CD-ROM drive can be used instead. It has a bigger buffer than a period-correct drive.
With CDSPEED utility, many CD-ROM drives cam be set to a slower, constant speed.
That way, they won't spin up/down all the time (causes jerky access).

https://www.sac.sk/files.php?d=14&p=8

Edit: Again, 4 MB is usually fine.
OS/2 starts to feel comfortable with 8 MB.
More than ~10 MB aren't useful, either.
The 15-16 MB area is the end of ISA address space and sometimes used by certain things as an i/o space
(16-Bit ISA VGAs, network cards etc). It's comparable to the 640KB-1MB area, maybe.

Windows 3.x doesn't really need more than 4MB, but it can benefit from large empty RAM.
That's because of memory fragmentation and the Windows memory management in general.

Windows 3.x wants free memory that's "contiguous",
also in parts because it's using a shared memory model and fixed starting points for the applications (they use relocation tables).

Long story short, with more free memory (more headroom), Windows doesn't need to shuffle around memory so much.

Edit: I did forget. SmartDrive or MSCDEX may also support EMS.
So someone can install a dedicated EMS board, which is separate from PC memory.

Edit: Pictures

PS: It's just meant as an orientation. A small cache (say 512KB) may do good enough already.
It just came to mind because I lived without SmartDrive for a long time, so the difference with/without is more apparent to me now.

Interesting, Thanks!

I've got a 386/25MHz (don't know if it's SX) with 16MB of RAM, DOS 6.20, and I run Windows for Workgroups 3.11 on it. It has a network card and can surf the internet (very slowly).

It should be fine for old DOS games of the 80s (Wolf-3D runs ok, but Doom is too slow). Small Windows games (such as the numerous card games) will be fine too. You can also install Office 4.x and do some word processing.

The maximum size of a hard drive will normally be 512MB. The bios can't handle more.

Robbbert wrote on 2024-01-06, 20:52:

I've got a 386/25MHz (don't know if it's SX) with 16MB of RAM, DOS 6.20, and I run Windows for Workgroups 3.11 on it. It has a network card and can surf the internet (very slowly).

It should be fine for old DOS games of the 80s (Wolf-3D runs ok, but Doom is too slow). Small Windows games (such as the numerous card games) will be fine too. You can also install Office 4.x and do some word processing.

The maximum size of a hard drive will normally be 512MB. The bios can't handle more.

My 386SX/20 has 20 MB of RAM. 4 of them are just available as EMS because of the 16 MB limit of an 386 SX.
It has a SoundBlaster 16 ASP. I've converted the Windows sounds to an ADPCM compressed format.
The hard disk has 1 GB and is on an Adaptec 1542B SCSI controller.
The graphics card is an ET4000/W32 ISA which is not just a fast frame buffer card but also has some graphics acceleration provided by the W32.
I just have an NE2000 compatible networking card in it.
I have dual boot DOS/WfW 3.11 and Windows 95B on it.

Yes, everything that uses the CPU is slow - like file decompression.
But it is still the mainboard from my first computer.

The other thing I am attempting to do at the moment is connect a 5.25" floppy drive to this machine, but I am having some issues.

I have two drives to test with, one is a "newer" Chinon FZ-506, the other is an older Toshiba 5426A0K out of an XT clone. I would like this machine to serve as a middleman between the XT and the modern world, since currently the only way to get things onto the XT is the floppys.

The bios for this machine only has two 5.25" configuration options, a 360k one and a 1.2M one. I was able to format and use a disk with the chin0n set to 1.2M, though it only showed about 422k of space. If either drive is set to the 360k mode it returns a track 0 error when formatting, and drive not ready or seek failure when trying to access another disk. The toshiba did not work on the 1.2M mode, even to format a disk. The disks I have are adacomp double sided, double density, 48TPI.

I am assuming that there is a mismatch of formats and densities, but not really sure beyond that.

Interesting practical example of a similar system:

I was digging through my pile of stuff to test and sell (or otherwise get rid of) I came across a tiny 386SX-25 system. It sounds very similar to what you have there - 4MB RAM (4x 1MB), 412MB HDD, 3.5" 1.44MB floppy, Trident SVGA onboard etc. - just no ISA slots, which is why I'm looking to offload it - not enough flexibility for me (and I already have a tiny 486SLC system that does have ISA).

So, how was it configured? It had 1MB configured as ramdrive, ran MS DOS 5.0 and Windows for Workgroups 3.11 (surprisingly well for such a limited system). The previous owner had been so kind as to add a text in AUTOEXEC.BAT stating that if you wanted to run big Windows programs, it would make sense to get rid of the ramdrive.

Now, doesn't mean you have to do the same, but it's an indication of what a clearly competent and knowledgeable user had configured back in the day to optimally use it.

Alex_03 wrote on 2024-01-06, 23:15:

[...]

since currently the only way to get things onto the XT is the floppys.

Getting the floppies working on this system is a good idea (I'm looking for a second 360kB DS/DD drive to do the same), but as for things onto an XT - IMHO network is the way to go.

I have an Intel 8/16 in mine. It's a pretty average 16b ISA NIC, but as the name suggests, it also works in an 8b slot. Then use Brutman's mTCP suite (shout out to great fellow Vogon 😀 ) to get that thing online. Trick on really old systems is to use them as FTP servers (FTPSRV.EXE). That lets you use a nice modern client on your current system (I use Filezilla) to move stuff to the old one.

Vastly easier, faster and more reliable than messing around with floppies.

Alex_03 wrote on 2024-01-06, 23:15:

The other thing I am attempting to do at the moment is connect a 5.25" floppy drive to this machine, but I am having some issue […]
Show full quote

The other thing I am attempting to do at the moment is connect a 5.25" floppy drive to this machine, but I am having some issues.

I have two drives to test with, one is a "newer" Chinon FZ-506, the other is an older Toshiba 5426A0K out of an XT clone. I would like this machine to serve as a middleman between the XT and the modern world, since currently the only way to get things onto the XT is the floppys.

The bios for this machine only has two 5.25" configuration options, a 360k one and a 1.2M one. I was able to format and use a disk with the chin0n set to 1.2M, though it only showed about 422k of space. If either drive is set to the 360k mode it returns a track 0 error when formatting, and drive not ready or seek failure when trying to access another disk. The toshiba did not work on the 1.2M mode, even to format a disk. The disks I have are adacomp double sided, double density, 48TPI.

I am assuming that there is a mismatch of formats and densities, but not really sure beyond that.

1,2MB is double sided, high density.
your disks are 360k.
you need different disks. or use them as 360k disks wich barely holds the command.com and selected tools like format
use format /4 (alternatively use format /f:360)
/4 should work if you want to format a 360k floppy in a 1,2mb drive.

i had exactly the same issue.

I noticed while testing some disks that my chinon drive is leaving scratches in the disk, two concentric rings toward the outside of the disk that line up with the top and bottom head. This seems bad, is there something that would cause this or a way to fix it?

That does sound bad. There might be some junk on the head, but be very careful if you try to clean it, as it's really easy to accidentally break them off instead.

I forgot to mention before that my machine has a 1.2MB drive as A: , and a 1.44MB drive as drive B: . The reason I have a 1.2MB rather than a 360k drive is I don't have any working 360k drives left. It's still capable of running "booter" floppies though.

The machine has a Turbo button, which is needed for the few games that refuse to start in fast mode.

In Windows, I have WS_FTP_LE installed, so I can use it to transfer files to/from my 2 NAS boxes.

In Windows, if you create a shared drive, it can be accessed by any later Windows, even Windows 10.

If you want to access a shared drive on another machine from your 386, you can connect to a win9x machine, but not anything newer.