Intel Above Board vs Doom... we all lose!

Take a deep dive into the Intel Above Board PS / AT with a 25MHz 486. Is it any good for running Doom? Is it any good as a disk cache? I'll examine using Central Point Software PC-Tool 4.2 disk cache on this system too!

00:00 Intro
01:21 Project background
03:36 Above Board overview
07:25 Prelude to fail
08:10 SpeedSys fail
09:02 Second Above Board
13:04 SpeedSys for real
19:08 It runs Doom
26:06 Disk cache instead?
28:24 Driver fail
32:10 Disk cache fail
33:44 Disk cache success
34:27 Benchmark setup
39:50 Data analysis
42:14 Disk loads during the demo
43:23 Should you use one?
46:06 Closing words

Documentation and drivers for Intel Above Boards (many models):

[minombredepila]

I really like your engineering approach, comparing results, times and effects. The matrix of screens was simply astounding. Your channel is clearly underrated, but for engineers like myself, this is the way of working. A pity not living in Portland to attend the gatherings in which you participate. Waiting here with popcorn and drinks for your next episode.

[geekwithsocialskills]

Wow. What a PITA addon board. I did enjoy your process, especially your "take that enter key" commentary LOL! All of your maniacal laughter was an added bonus as you banged your head working on this project. I was surprised to hear that you don't own a 286.

[chaoticsystem]

I just had started my first job when that factory burnt down. A colleague had a tiny company and offered to get everyone cheaper ram. The order got fucked up and instead of sending 20k worth of ram, we got 10x as much. The store didn't wanna take it back at first and stalled for a week. Until that factory popped. The guy who ordered had to get a mortgage on his house and his wife went ballistic...
The ram he had sold in under a week and with such a profit that we all got free ram...

[denniseldridge]

My impression was that the Above Board was intended to, in turn, backfill the IBM PC AT's 512K to 640K and then provide extended/expanded memory for the emerging applications that could use it. I just remember spending an inordinant amount of time trying to get the settings right with whatever motherboard I was working with at the time lol.

[foobar]

I think the slow performance is probably because the cache controller can't deal with memory behind the isa bus. You should try it with level 2 cache tho. My memory is fuzzy but I think the L2 is controlled by the chip set not the cpu on 486? Would be an interesting test.

[BrassicGamer]

When you said that the Doom benchmark took over 4 hours I was laughing so hard. I thought it was tough watching a 25MHz 486 do it with a VLB graphics card. Jeeez. And then I started thinking, are creators like us just... wasting our time? I often feel like that, but I realised that this video is the perfect example of "Hey, don't do this, it's a waste of time!", which means you didn't waste your time. So thank you for your in-depth endeavours. I have one of these expansion boards (a 'Six Pack' clone, it seems) and I am looking forward to(?) testing it with my AT Clone.

[chaoticsystem]

How about a cache controller? I remember having one in a local bus 486 and it made a quite a difference.

[leecremeans]

OMG I remember doing exactly this when I had a 486 in, like, my senior year of high school. There wasn't enough RAM on the motherboard to do much, but we had one of the 16-bit Above Boards (one of the later ones with a config EEPROM on it) around, so...

I remember Descent (which i was kind of obsessed with at the time) slideshowing with this board in. I don't think I had a copy of Doom, so I never tried it, but anything that required 386 protected mode absolutely crawled. The situation for me didn't improve until I got a Pentium for college later in 1995.

[Shmbler]

Thats about the craziest retro experiment I've seen in a long time. I would not have expected that thas these boards even work on 386/486. Which now brings the question: Will it work on a Pentium/2/3/4 or K7 systems with an ISA bus?

[Kakariki]

My old dad's XT clone had a BocaRAM card installed with 2Mb EMS, believe he used it for Symphony and Lotus software, he worked a lot with spreadsheets and other financial stuff for his job.

For some reason the card stayed around but I used most of the RAM chips to upgrade old 8bit home computers.

The card itself is there still but plucked empty, maybe I will repopulate that card and have some fun with an old 286 system I still have

[prozacgodretro]

Iirc ... L1 cache it's not even connected to the isa bus, it is directly connected to the memory controller. L2 cache is available on the isa bus...

But I could be wrong. It's been a few years.

[matthewday]

Would 256k L2 mitigate the very slow RAM

[BGBTech]

Just ran into this channel...

But, ironically, those framerates are not much faster than I get when running Doom inside a Verilator simulation for a custom CPU core. Say, it is a logical 50MHz CPU core getting around 20-25 fps in Doom, custom ISA, but the Verilator simulation is around 250x slower than real-time, so say around 10 or 12 seconds per frame...
The CPU core can also be run on an FPGA board, such as the "Nexys A7" or similar.
Where, Verilator allows running ones' Verilog (HDL) code on a normal computer, but it is not exactly fast...

Debatable if terribly worthwhile, but in-general my ISA seems to be faster than RISC-V (the same CPU was modified to also have an alternate decoder for RISC-V; for running Doom it seems to be around 22% faster than RV64G with "GCC -O3"'; for Quake and Dhrystone they are currently closer to tied; I also have a GLQuake port, which is no contest, as my ISA wins by a large margin, likely due to my OpenGL implementation being somewhat optimized around SIMD).


But, yeah, kinda funny to see Doom running at these sorts of speeds on actual hardware...

[memadmax]

This scenario would've never, ever, happened with me...

Cause I would've been upgrading from a 386 lol ^.^

[JimLeonard]

Got a like in the first 5 seconds for the shirt alone!

[rzmtz]

great video again! most entertaining. thats a lot of one thousands between frames.

[oidpolar]

It's ISA 16bit, so unfortunately, it will be slow