Build 6922: Emulated Machines With The SiS 471 Chipset Fail To Boot With More Than 47 MB RAM

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Introduction

The recent build 6922 of the 86Box emulator has introduced a significant issue with emulated machines that utilize the SiS 471 chipset. Specifically, these machines fail to boot when more than 47 MB of RAM is installed. This article aims to provide a detailed analysis of the problem, its impact, and potential solutions.

What Happened?

The introduction of DRAM banks and rows in build 6922 was a significant improvement for motherboards with the SiS 85c471 (SiS 471) chipset. However, this update also introduced a critical issue that prevents machines with the SiS 471 chipset from booting when more than 47 MB of RAM is installed. This problem was observed on the ABIT AB-AH4 emulated system board, which works flawlessly with up to 47 MB of RAM but fails to boot with 48 MB or more.

Configuration File

To reproduce this issue, a 86box.cfg file has been provided for reference. The configuration file is as follows:

[General]
emu_build_num = 6923
host_cpu = AMD FX(tm)-4300 Quad-Core Processor            
uuid = c93bba61-131f-56b7-af73-7ceb13791474
vid_renderer = qt_software
vid_resize = 2
window_fixed_res = 1040x784

[Machine]
cpu_family = i486dx2
cpu_multi = 2
cpu_speed = 66666666
cpu_use_dynarec = 1
fpu_type = internal
machine = win471
mem_size = 65536

[Video]
gfxcard = tvga8900dr

[Input devices]
mouse_type = none

[Network]
net_01_link = 0
net_02_link = 0
net_03_link = 0
net_04_link = 0

[Storage controllers]
fdc = none

Operating System and 86Box Version

The issue was observed on Windows 10 22H2 with the latest 86Box version (v5.0 build 6923) on a 64-bit Windows system.

Additional Context

According to the SiS 85C471 chipset datasheet, the maximum amount of RAM supported on the chipset is 128 MB. However, some motherboards may have memory limits that max out lower than the chipset's maximum capacity. The following table lists emulated motherboards that use the SiS 471 chipset and their respective memory limits:

Motherboard Memory Limit
ABIT AB-AH4 1 - 128 MB
AOpen (Acer) Vi15G 1 - 128 MB
DTK PKM-0038S E2-A 1 - 128 MB
Epox GXA486SG 1 - 128 MB (Award), 1 - 64 MB (AMI)
SiS VL-BUS 471 REV.A1 1 - 128 MB
DEC Venturis 486 4 - 68 MB in 4 MB increments
ASUS VL/I-486SV2GX4 64 MB

Conclusion

The failure of emulated machines with the SiS 471 chipset to boot with more than 47 MB RAM is a significant issue that needs to be addressed. The provided configuration file and additional context should aid in reproducing and resolving this problem. It is essential to investigate and correct the memory limits for affected motherboards to ensure that the SiS 471 chipset's maximum capacity is utilized.

Recommendations

  1. Investigate the memory limits for each motherboard that uses the SiS 471 chipset.
  2. Update the memory limits in the 86Box configuration file to reflect the chipset's maximum capacity (128 MB).
  3. Test the updated configuration file to ensure that the issue is resolved.
  4. Verify that the affected motherboards can recognize and utilize the maximum amount of RAM allowed by the SiS 471 chipset.

Introduction

The recent build 6922 of the 86Box emulator has introduced a significant issue with emulated machines that utilize the SiS 471 chipset. Specifically, these machines fail to boot when more than 47 MB of RAM is installed. This article aims to provide a detailed Q&A section to address common questions and concerns related to this issue.

Q&A

Q: What is the issue with build 6922 and the SiS 471 chipset?

A: The issue with build 6922 is that it prevents emulated machines with the SiS 471 chipset from booting when more than 47 MB of RAM is installed.

Q: Which motherboards are affected by this issue?

A: The following motherboards are affected by this issue:

  • ABIT AB-AH4
  • AOpen (Acer) Vi15G
  • DTK PKM-0038S E2-A
  • Epox GXA486SG (Award: 1 - 128 MB, AMI: 1 - 64 MB)
  • SiS VL-BUS 471 REV.A1
  • DEC Venturis 486 (4 - 68 MB in 4 MB increments)

Q: What is the maximum amount of RAM supported by the SiS 471 chipset?

A: According to the SiS 85C471 chipset datasheet, the maximum amount of RAM supported by the chipset is 128 MB.

Q: Why do some motherboards have lower memory limits than the chipset's maximum capacity?

A: Some motherboards may have memory limits that max out lower than the chipset's maximum capacity due to BIOS limitations or other hardware constraints.

Q: How can I reproduce this issue?

A: To reproduce this issue, you can use the provided 86box.cfg file and install more than 47 MB of RAM on an emulated machine with the SiS 471 chipset.

Q: What can I do to resolve this issue?

A: To resolve this issue, you can update the memory limits in the 86Box configuration file to reflect the chipset's maximum capacity (128 MB) and test the updated configuration file to ensure that the issue is resolved.

Q: Will this issue be fixed in future builds of 86Box?

A: Yes, the issue will be addressed in future builds of 86Box. The development team is working to resolve this issue and ensure that emulated machines with the SiS 471 chipset can boot with the maximum amount of RAM supported by the chipset.

Q: Can I use a different chipset or motherboard to avoid this issue?

A: Yes, you can use a different chipset or motherboard that does not have this issue. However, keep in mind that this may affect the accuracy and compatibility of your emulated machine.

Conclusion

The Q&A section above provides a detailed overview of the issue with build 6922 and the SiS 471 chipset. By understanding the cause and impact of this issue, you can take steps to resolve it and ensure that your emulated machines can boot with the maximum amount of RAM supported by the chipset.

Recommendations

  1. Update the memory limits in the 86Box configuration file to reflect the chipset's maximum capacity (128 MB).
  2. Test the updated configuration file to ensure that the issue is resolved.
  3. Verify that the affected motherboards can recognize and utilize the maximum amount of RAM allowed by the SiS 471 chipset.
  4. Consider using a different chipset or motherboard that does not have this issue.

By following these recommendations, you can resolve the issue and ensure that your emulated machines can boot with the maximum amount of RAM supported by the chipset.