OK, I implemented that change via modbin into the bios, and verified with my DOS tool that dumps the registers for this board (which I will post here as well). Register changed as expected.

Benchmark scores before and after are attached. I only ran one test so far, but definite improvement. Not sure if this is consistent with what you have experienced.

Yes, that drop from 78 us/KB to 35 us /KB comes from switching from always dirty to 7+1

Attached is the modified BIOS in the event anyone else needs it. This is the 4/27/94 BIOS with the one small tweak from 0 to 1 on register 72 to properly set L2 dirty tag. Thanks @jakethompson1 for the idea!

It took me a little while to locate modbin, so here it is on the Internet Archive. I used 4.50.80 for this change.
https://web.archive.org/web/20090206020432/ht … om/download.php

sweet bump, how does it translate to benchmarks/doom scores? Im failing terribly finding benchmarks in that dirty bit thread 🙁

I'm not yet on to testing with apps.

On the CPU side, I have the POD83, two Am5x86 133s (including an ADZ chip that should be overclockable), and a Cyrix 5x86-100GP so I need to finish testing and figure out which one will be the best option.

I also have disk testing, as I have the Adaptec 2842A and the Buslogic BT-445S to try out with my ZuluScsi. And I just picked up a Promise EIDE2300 Plus (per the recommendation on this forum) to try with CF cards.

My video card is currently a Diamond Stealth64 Graphics 2000 (Vision 868 VLB) with 1MB. I do have an additional 1MB of memory but it didn't detect it, so I have another few memory chips on order.

Once I get it fully dialed in with hardware I will post some benchmarks for doom, etc.

OK, here goes the first post about disk access.

This has been via my Gigabyte GA-486VF / SiS 85C471 system with an AMD Am5x86-P75, with a comparison between a BusLogic BT-445S and an Adaptec AHA-2842A.

System/config used for both cards:

• Motherboard: Gigabyte GA-486VF
• Chipset: SiS 85C471
• CPU: AMD Am5x86-133 P75
• CPU speed: ~133 MHz, 4x multiplier, ~33.2 MHz bus
• RAM: 64 MB (it has 128 installed, DOS can only use 64)
• Video: Diamond Stealth64 Graphics 2000 / S3 Vision868 VLB, currently detected as 1 MB
• Storage device: ZuluSCSI Blaster, rev 2025f, recent firmware (I updated it sometime in April 2026 - I didn't note the specific version)
• SANDISK 128GB Extreme PRO SD UHS-I Card
• DOS: MS-DOS 6.22
• BIOS: Award Modular BIOS v4.50G, modified with MODBIN
• SiS register 72h changed in the Award chipset defaults from X0000010 to X0000110, so the L2 dirty/tag behavior is set during POST

BIOS/chipset settings:

• Turbo: ON
• Cache Burst Read: 0W
• Cache Write Cycle: 0W
• Latch Local Bus: T2
• External cache: Write Back
• Internal cache BIOS setting: Write Back
• System Shadow: Cached
• Video Shadow: Cached

Adaptec AHA-2842A setup:

• Adaptec AHA-2842A VLB, BIOS version 2.0 (unmodified - ie not patched for int13 support)
• Adaptec write-back jumper enabled on the card itself
• Everything else identical to the BusLogic test

Adaptec results:

• SpeedSys CPU score: 47.80
• SpeedSys memory bandwidth: 74.39 MB/s
• SpeedSys L1 data cache: 73.34 MB/s
• SpeedSys L2 data cache: 42.10 MB/s
• SpeedSys memory throughput: 24.25 MB/s
• SpeedSys VESA/video throughput: about 13420 KB/s
• SpeedSys hard drive score: 193.38
• SpeedSys buffered read: about 5189-5190 KB/s
• SpeedSys linear verify: about 3146 KB/s
• SpeedSys linear read: about 2423-2429 KB/s

DiskTest 2.3, Adaptec:

• Write speed: 3385.12 KB/s
• Read speed: 4137.37 KB/s
• 8K random, 70% read: 145.5 IOPS
• Sector random read: 180.3 IOPS
• Average access time: 6 ms

BusLogic BT-445S setup:

• BusLogic BT-445S VLB, BIOS version 4.72
• Everything else identical to the Adaptec test

BusLogic SpeedSys results:

• SpeedSys CPU score: 47.80
• SpeedSys memory bandwidth: 74.39 MB/s
• SpeedSys L1 data cache: 73.34 MB/s
• SpeedSys L2 data cache: 42.10-42.19 MB/s
• SpeedSys memory throughput: 24.25 MB/s
• SpeedSys VESA/video throughput: about 13419-13421 KB/s
• SpeedSys hard drive score: 215.38-218.82

BusLogic SpeedSys HDD details:

• Average / max seek: about 4.02 / 4.04-4.08 ms
• Random seek: 4.11 ms
• Track-to-track seek: 3.81 ms
• Random access time: about 5.26-5.32 ms
• Buffered read: about 4924-5065 KB/s
• Linear verify: about 3270-3305 KB/s
• Linear read: about 1976-2140 KB/s

DiskTest 2.3, BusLogic:

• Write speed: 3250.79 KB/s
• Read speed: 2748.99-2864.34 KB/s
• 8K random, 70% read: 141.4 IOPS
• Sector random read: 186.9 IOPS
• Average access time: 5 ms

Quick comparison:

• CPU/cache/memory results are effectively identical between the two cards, which is good since the only intended variable was the SCSI card.
• The BusLogic has the higher SpeedSys composite hard-drive score: about 218.82 vs 193.38 for the Adaptec.
• The Adaptec does better in DiskTest sequential read: about 4137 KB/s vs 2750-2864 KB/s for the BusLogic.
• The Adaptec is also slightly ahead in DiskTest write: 3385 KB/s vs 3251 KB/s.
• The BusLogic is slightly better in DiskTest sector random read: 186.9 IOPS vs 180.3 IOPS.
• The BusLogic also shows a slightly better average access time in DiskTest: 5 ms vs 6 ms.

I’m not sure I’d call either card the absolute winner yet. The Adaptec looks better in DiskTest sequential throughput, especially reads, while the BusLogic scores better in SpeedSys’s overall HDD score and a couple of smaller/random metrics.

Next step will be to test with a Promise EIDE 2300 Plus with a 4GB industrial CF card.

So I spent a ton of time dealing with what seemed like random memory corruption. I suspected the external cache chips after much testing, and spent hours researching every 1990s-era tool to check and test cache. Cachechk, ctcm, cct386, speedsys, etc. Windows 95 was intermittently failing to load or process the registry. So I pulled the 4 chips (512kb) of cache and went to 8 chips (256kb). Same results. Then I went to 4 chips (128kb) and it worked - no issues!

It was after this point - many hours into the process - where the software-first brain in my head was looking for more ways to test cache chips. Even thinking of writing a program to do it. When I finally realized, HMM I wonder if this very nice TL866 eeprom programmer sitting next to me might have the ability to test chips. In what many on this forum would recognize as a blinding glimpse of the obvious - why yes it can test chips! So I popped them in one at a time and found one chip in the 512kb arrangement was bad, and 2 chips in the 256kb arrangement were bad. I just lucked out that the 4 I selected for 128kb were all good chips or I'd still be here pulling what remains of my hair out.

Oh, and the bus jumper had come off so instead of 33MHz it was 40MHz. Also not super helpful.

Long story long, I'll retest and post actual results when the new cache chips arrive. In the meantime if someone is having problems with their SRAM cache chips in the future - don't overlook your eeprom programmer! My actual SRAM chips were not listed as options in MiniPro but a different vendor with the same package worked fine.

IE instead of selecting my chip:
IS61C1024-15N = 128K × 8 SRAM = 1 Mbit

I used:
W24010 = 128K × 8 SRAM = 1 Mbit

Under 5 minutes to test all of them.

Ah, we should have pointed that out. Especially with the IS61C1024 chips, if they're from ebay, they're about 10% defective, almost as if wherever they came from, they were pulled off the production line before going through the testing stage.

rjbrown99 wrote on 2026-06-08, 01:57:

So I spent a ton of time dealing with what seemed like random memory corruption. I suspected the external cache chips after much […]
Show full quote

So I spent a ton of time dealing with what seemed like random memory corruption. I suspected the external cache chips after much testing, and spent hours researching every 1990s-era tool to check and test cache. Cachechk, ctcm, cct386, speedsys, etc. Windows 95 was intermittently failing to load or process the registry. So I pulled the 4 chips (512kb) of cache and went to 8 chips (256kb). Same results. Then I went to 4 chips (128kb) and it worked - no issues!

It was after this point - many hours into the process - where the software-first brain in my head was looking for more ways to test cache chips. Even thinking of writing a program to do it. When I finally realized, HMM I wonder if this very nice TL866 eeprom programmer sitting next to me might have the ability to test chips. In what many on this forum would recognize as a blinding glimpse of the obvious - why yes it can test chips! So I popped them in one at a time and found one chip in the 512kb arrangement was bad, and 2 chips in the 256kb arrangement were bad. I just lucked out that the 4 I selected for 128kb were all good chips or I'd still be here pulling what remains of my hair out.

Oh, and the bus jumper had come off so instead of 33MHz it was 40MHz. Also not super helpful.

Long story long, I'll retest and post actual results when the new cache chips arrive. In the meantime if someone is having problems with their SRAM cache chips in the future - don't overlook your eeprom programmer! My actual SRAM chips were not listed as options in MiniPro but a different vendor with the same package worked fine.

IE instead of selecting my chip:
IS61C1024-15N = 128K × 8 SRAM = 1 Mbit

I used:
W24010 = 128K × 8 SRAM = 1 Mbit

Under 5 minutes to test all of them.

Sometimes it depends on BIOS cache settings - my original W24512AK-15 and non-original IC61C1024-15N both stable with some settings and randomly craches with other