DTK PKM-5031Y
With AMD 386 CPU at 50MHz mem bandwidth is at 105 Mb/s.
With SXL2 at 50/55 MHz is much higher.
But memory bandwidth is meaningless metric really.

So after I got that other DRx2 33/66 working this is my newest project: overclocking my Ti SXL2 to 33/66 MHz

CPU: Ti SXL2 25/50 running at 33/66 with added heatsink and fan
Motherboard: PC-Chips M326 G.W386/486 (like this one here https://www.ultimateretro.net/de/motherboards/5265)
Chipset: it says SARC but I found out that it's actually a UMC491-F
Cache: 128kB 15ns
BIOS: Swapped the Award with a MR BIOS that was designed for another UMC491-F board
Memory: 4x4MB 60ns
HDD: CompactFlash 512MB
Video: ISA 512kb AVGA2 (Cirrus Logic 5402)

Sidenote: it's interesting to see how the SXL2 outperforms the DRx2 by about 12% (in PCP, 3DB and Doom) at the same clock frequency due to the larger 8 kb L1 cache. (now if I only could get a IBM Blue Lightning 33/66 CPU)

Is your 5V SXL2 at 66 MHz able to complete Quake and load Windows?

feipoa wrote on 2022-03-29, 22:35:

Is your 5V SXL2 at 66 MHz able to complete Quake and load Windows?

I'll pop in an FPU and try the Quake test. Win 95 installed without problems, but I ran into some exceptions when I ran some Winamp tests. Not quite sure it it's the CPU or the ISA bus that runs at 16 MHz, thou. Need to test this further.

Edit: ran the Quake benchmark and had no problems

CPU Intel 80386 SX 20 MHz
BOARD Topcat Chipset
BIOS QuadTel
RAM 20 MB RAM (16 MB + 4 MB EMS)
SCSI Adaptec 1542B
HDD IBM DPES-31080
NET Intel EtherExpress PRO/10
SOUND SB16 CSP
VGA TSENG ET4000 W32 ISA

I'm sorry, I could not find a working VESA driver but tlivesa.com for vanilla ET4000 with VESA 1.2 support.

Windows 95 is running quite smooth for a slow clocked 386SX. .WAV system sounds are converted from 8-bit PCM via 16-bit PCM to 4-bit CT-ADPCM and decoded by CSP chip. GUI acceleration is done by Tseng ET 4000 W32. HDD access is done by busmaster Adaptec 1542B.

Wanted to share some notes about SXL2 CPUs based on past findings.

SXL2-50 has very high chance of running at 60-66 MHz but only on relatively slow motherboards.
For example this one - native 60MHz (no clock doubling), yet performance is lacking.

On fast clock-to-clock motherboards SXL2-50 does not climb much higher than its specification - tends to max-out at around 55MHz and even that is not very stable.
Below is a Quake 1 score from such system running at 50MHz natively (no clock doubling). Completely stable.
Number can be 3.6 fps if push things to 55MHz at compromised stability - mostly attributed to FPUs getting flaky in the context of Quake 1 and other apps demanding co-procs. So far haven't seen 40MHz rated FPU handling well 55MHz natively on fast board.

I too have noted a performance ceiling around 55 MHz on the SXL2 w.r.t. slow motherboards, e.g. VIA 481/495 based. JohnBourno, did you notice much performance gain between the SXL at 55 MHz compared to 66.6 MHz?

Unfortunately, the M326 mainboard doesn't have a dedicated crystal that I could swap out, so I'm limited to 25/33/40 MHz CPU clock.

My other 386 mainboard has a crystal socket, but it doesn't like to go faster than 45 MHz system clock, so hard to test the 55 MHz non-doubled clock with the SXL2.

pshipkov wrote on 2022-03-31, 05:25:

Wanted to share some notes about SXL2 CPUs based on past findings.

SXL2-50 has very high chance of running at 60-66 MHz but only on relatively slow motherboards.

I'm curious, what's the fastest results you got with an ISA bus based386 board? So in terms of 3D Bench and PC Player.

Wow, it looks like I did pretty much every single benchmark I know of except Speedsys on my 386SX-25 🤣

System Specs:
AT Mid Tower (No-Name)
TASK 230W AT
Scamp 386SX
AMD Am386SX/SXL-25
4MB (4x1MB FPM30)
Mitsumi 3.5" DS-HD
512MB CF/IDE (Internal)
CF/IDE (External)
ASUS 50x CD-ROM IDE
Cirrus Logic CL-GD5402 ISA 512KB
Edison Gold-16 (ES688)
MS-DOS 5.0/Windows 3.0

JohnBourno wrote on 2022-04-08, 09:05:

I'm curious, what's the fastest results you got with an ISA bus based386 board? So in terms of 3D Bench and PC Player.

Superscape - 50 fps
PC Player Benchmark - 11.2 fps
Wolf3D - 75.8 fps
Doom - 27.2 fps
Quake1 - 4.1 fps
more details here

Attached my 386SX25@27,5MHz. ISA and DMA @ 12MHz

CPU: AM386DX-40
FPU: IIT 3C87-40
Motherboard: FIC 4386-VC-HD
Chipset: VIA VT82C495 (Venus)
Cache: 256KB 20ns with 20ns TAG RAM and 15ns Alter / Dirty TAG RAM for write-back
BIOS: Award 4.20 version 1.15K with "Fast" DRAM Timings and "Turbo" Cache Timings
Memory: 20MB (4x1MB 70ns + 4x4MB 60ns, both Hitachi)
HDD: Maxtor 7540AV 504MB (jumpered for 1024 cyl)
Video: ISA 1024KB Cirrus Logic 5429
no overclocking (ISA / VGA or CPU)

Even with the "Turbo" setting, cache timings appear to be rather conservative, so I don't believe faster chips would change anything.

Other Dosbench scores
PC-Player VGA Bench: 4.0
Superscape: 14.7 / 14.5 (slower / faster systems)
Doom slow PCs: 28.34fps (2635 realtics)
Topbench: 79
Chris' Bench score: 13.2