I just looked too and the AMI, Award, and Acer BIOSes for this look pretty sparse.
Since they are uncompressed you can run a "strings" utility (e.g. on Linux or the Sysinternals version for Windows) and look for interesting strings/possible hidden options even if you don't have or can't open them in modbin, amibcp, etc.
It looks like the Acer BIOS has a hidden memory type settings, where "Slow" is for 80 ns or slower. That's probably part of what you are looking for. [edit: it's not hidden, I just didn't know about Page Down] But I see nothing at all about 486 cache burst settings.

Another indication that not much is known about this chipset is there is no emulation for it in PCem or 86box.

I didn't see the Acer BIOS for the M1419. Do you know what kind of system it came from?
Too bad there aren't any utilities for dealing with Acer BIOS. I have a pretty sweet dual Pentium system that has an Acer BIOS, and I'm not aware of any replacement options.

In the FTDI chipset "manual" I did find some registers to control 486 burst mode timings:

36h
Bit 7 Internal local bus control
0 Disabled
1 Enabled
Bit 6 486 burst mode
0 Disabled
1 Enabled
Bits 5-4 Low speed rate selection
00 1:6 01 1:2
10 1:3 11 1:4
Bit 3 Cache write algorithm
0 Wrt/Thru
1 Wrt/Back
Bit 2 Refresh type
0 AT Bus
1 Hidden
Bits 1-0 486 burst mode timing
00 3-2-2-2 01 3-1-1-1
10 2-2-2-2 11 2-1-1-1

This may or may not work on the Acer M1419 chipset.

Thank you for finding that snippet about the write back/thru bit!
I'd like to try punching that into CTCHIP to see if I can get these ALi M1419 386DX boards to stop using broken write back. 😅

This is all I get in Advanced Chipset menu on https://theretroweb.com/motherboards/s/acer-i … gxi-model-i433a

I got a Bioteq 82C3480 version of this. I'm running a 486DX CPU, L2-cacheless for now as it came with 25 ns chips.

In debug,
-i fca0
appears to be the RAM speed register, seems autoconfigured to 15h for 486DX-25 MHz, and 11h for 486DX-33 MHz or greater. That setting seems pessimistic.

-o fca0 15 will make it faster (at 33 MHz and higher)
-o fca0 17 will make even faster.

It doesn't appear to go beyond 17 or below 11, the machine locks up if you set it as such.

With fca0=17, and at DX-33 MHz, the system's RAM speed appears on-par with a maxed-out UMC 491 with external cache also disabled (to avoid conflating with the "always dirty" issue).
With fca0=17 and at DX-50 MHz, it's around the same speed, 51 us/KB for RAM. As it won't post at 50 MHz without JP10 closed, I suspect JP10 might be the "delay ALE by one cycle" for this board (MB-1433/50AEA).

Another user with a 386DX-33 board found fca0 to be set to 14h, so perhaps the bottom bit is 0 for 386 and 1 for 486

Anonymous Coward wrote on 2024-07-20, 14:15:

I didn't see the Acer BIOS for the M1419. Do you know what kind of system it came from?
Too bad there aren't any utilities for dealing with Acer BIOS. I have a pretty sweet dual Pentium system that has an Acer BIOS, and I'm not aware of any replacement options.

BitWrangler wrote on 2024-11-01, 16:07:

This is all I get in Advanced Chipset menu on https://theretroweb.com/motherboards/s/acer-i … gxi-model-i433a

Do you still have your M1419 boards?
As the BIOS obviously doesn't tell us, I have to rely on benchmarking to determine the L2 cache speed. These are seemingly hardcoded for 2-1-1-1 when using a 486, when I compare the L2 cachechk for a 486DX-33 in these vs. a comparable UMC. It's too bad as I wanted to use the MB-1433/50-AEA for 50 MHz operation, but seems I'd have a tough time getting external cache to work.

jakethompson1 wrote on 2025-08-06, 01:03:

Do you still have your M1419 boards?
As the BIOS obviously doesn't tell us, I have to rely on benchmarking to determine the L2 cache speed. These are seemingly hardcoded for 2-1-1-1 when using a 486, when I compare the L2 cachechk for a 486DX-33 in these vs. a comparable UMC. It's too bad as I wanted to use the MB-1433/50-AEA for 50 MHz operation, but seems I'd have a tough time getting external cache to work.

Still have it, but not set up and workbench occupied... had a look through my screenshots though, this is the only one that seemed vaguely relevant, was running at 40Mhz with a U5S in, settings probably same as above BIOS shot. IDK if you can work much out from it...

That's either turbo button or something else horribly wrong

Possibly it was the hidden refresh not turned on, there's a lot of stuff that was way faster with it enabled.

These are stats with an Intel 486dx-33 with the chipset bit hack up above. I'm not able to use Hidden Refresh and External Cache together or the system will lock up. Obviously if you have to pick between the two it's external cache.

1 CACHECHK v4 2/7/96  Copyright (c) 1995 by Ray Van Tassle. (-h for help)
2 CMOS reports: conv_mem= 640K, ext_mem= 19,456K, Total RAM= 20,096K
3 Clocked at 486 33.0 MHz
4 Reading from memory.  
5 MegaByte#:      --------- Memory Access Block sizes (KB)-----
6       1    2    4    8   16   32   64  128  256  512 1024 2048 4096 <-- KB
7 0:   32   32   32   32   37   37   37   37   37   53   --   --   --    µs/KB
8 1:   32   32   32   32   37   37   37   37   37   54   54   53   54    µs/KB
9 2  3  <--- same as above.
10 4:   32   32   32   32   37   37   37   37   37   54   54   54   54    µs/KB
11 5:   32   32   32   32   37   37   37   37   37   54   54   53   54    µs/KB
12 6  7  8  <--- same as above.
13 9:   32   32   32   32   37   37   37   37   37   54   54   54   54    µs/KB
1410 11 12 13 14 15 16 17  <--- same as above.
1518:   32   32   32   32   37   37   37   37   37   54   54   53   --    µs/KB
1619  <--- same as above.
17
18 Extra tests----
19 Wrt  32   32   32   32   32   32   32   32   32   32   32   32   32<-Write mem
20 This machine seems to have one cache!? [read]
21    !! cache is 256KB --  29.7 MB/s  35.3 ns/byte  (144%)          4.4 clks
22    Main memory speed --  20.6 MB/s  51.0 ns/byte  (100%) [read]   6.4 clks
23    Effective RAM access time (read ) is 204ns (a RAM bank is 4 bytes wide). 
24    Effective RAM access time (write) is 123ns (a RAM bank is 4 bytes wide). 
25    Clocked at 486 33.0 MHz.  Cache ENABLED.
26 Options: -t0