swarm

SGI Indy (1993)

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This machine represented the SGI’s low-end workstation offering. It was targeted towards Mac users (DTP…) that needed more graphics and processing power than they could get from Macintosh Quadra systems. It’s a sleek pizza-box computer with just a single quiet fan inside (unlike other SGI systems). However, in comparison with non-SGI competitors, it was not slow. It had at least 100-MHz (64bit) MIPS processor, at least 16MB of RAM (reasonable configurations started with 32MB) and multiple graphics card options available. 10Mbit/s LAN, ISDN modem and video inputs (composite / S-Video / a digital port for the bundled webcam) were integrated on the logic board in all configurations as standard.

My Indy is from 1995 and has a more powerful 150MHz MIPS R5000 CPU. On the other side, it is equipped with the lowest possible graphics card (XL8/XGE8/Newport) that supports no more than 256 colors and was introduced with the early machines.

I always thought that Indy was the only SGI system without any 3D acceleration when sold with XL8 (2MB of 64bit video RAM) or XL24 (6MB of 192bit video RAM for true color modes) graphics cards. I expected just a crappy framebuffer (with BitBlt) and nothing more – like in Sun and HP machines. I was wrong. The REX3 chip inside the Newport graphics is pretty capable. Although all the 3D transformations and triangle setup are done in software, the chip can raster triangles with smooth (Gouraud) shading and per-vertex alpha-blending. Even Z-Buffering is partially accelerated using the chip (Z-Buffer is stored in system memory though).

In fact, this chip is not very far from early PC 3D accelerators (1996-1997) in terms of functions… except for the texturing support which was not available even with higher-end workstation-class 3D accelerators in 1993. This is for the first time I see 3D accelerated OpenGL (1.0) on such an old graphics card – and in 256 colors. To be correct, the scene with triangles has just 16 colors because any real-time graphics requires double-buffering. Each byte of the window in video memory contains one pixel from both buffers in the GBRG-GBRG arrangement of bits.

The graphics card is faster than I would expect. The pixel fill rate for smooth shaded triangles is ~50Mpix/s. If you add alpha-blending, you will get ~20Mpix/s. That’s 5-20 times as fast as the Windows NT 4.0 software renderer on a laptop with 133-MHz Pentium MMX and a 2D-only graphics chip. The speed in 3D is more comparable with 3Dlabs Permedia, S3 Virge DX and other consumer 3D accelerators from 1996.

A Sound Card David Made 30 Years Ago

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This is a sound card designed and built by David (a friend of mine who does most of hardware repairs here on my tumblr) in the early 90s. He was a 15-16 years old high school student when he created this thing. It’s a custom design with 12-bit DAC, DMA support and connections for mono out and mono in. He was forced to use an 8-bit ISA bus because 16-bit AT prototyping card PCBs were not available in Czechoslovakia stores at the time (not long after the Velvet Revolution). There was also a problem to get necessary parts for stereo output.

The sound card is not compatible with any standard, so he wrote a program to playback wave sounds and created a “driver” for MODPLAY to playback tracker music. His reason to make his own sound card was simple – 8-bit Sound Blasters had worse sound quality and 16-bit sound cards were too expensive for him.

He still has one of the assembled cards, a prototyping board, all technical drawings and a WordPerfect document describing the design and operation of the card.

There is a quick video of the working card: https://www.youtube.com/watch?v=rL8u9aRfaK8

Video Like From the 1980s

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My employer obliged me to make a video as a part of a sales training totally unrelated to my technical job role. I decided to make it like from the 1980s (including intro music generated by a Yamaha TX81Z FM synthesizer) so I took two Sony Handycams, a VHS recorder, some musical equipment and an old laptop with Firewire. The result was recorded to a VHS tape and back three times before I was satisfied with the picture and sound quality degradation.

 

Repairing IBM PS/2 P70 before Bytefest

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I shared a photo of computers we brought to Bytefest (a vintage computer show in Czech Republic). IBM PS/2 P70 was one of those which needed fixing before the show. In this case, there were issues with an Alps floppy drive and power supply. I have to admit that this was one of the most painful disassemblies we did.

This is a dream machine for a user but total nightmare for maintenance. One example – it was necessary to disassemble a half of the unit just to connect a floppy cable back to the drive.

Bytefest 2018

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I’ve brought some of my computers to Bytefest (a big Czech vintage computer show): Apple PowerBook 100 with an external floppy drive, IBM PS/2 P70 as a cool gas-plasma-screen serial terminal, SGI O2 (used only as a hard drive cloning machine running in headless mode), SGI Octane2 with all necessary peripherals and DELL Precision M50 for sharing wireless Internet connection with my other machines (and also to show how the graphics workstation market changed in less than two years from Octane2).

Insignia SoftWindows 95

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PC compatibility was a big thing for UNIX workstation manufacturers in the 80s and 90s. It started with x86/DOS emulators for text-only applications and later evolved in products like SoftWindows 95. This is a full x86 emulator with pre-installed and pre-configured Windows 95 in it and Insignia ported the emulator for non-PC platforms including IRIX, Solaris, HP-UX, MacOS, NeXT and other systems.

I have to say that installing the emulator on SGI IRIX is way easier than I expected. Just insert the installation CD, run the IRIX Software Manager, confirm the installation and that’s it. The first start of the emulator installs the Windows 95 by copying all the files on the virtual hard disk and deploying device drivers. It took maybe three minutes and didn’t require any user interaction.

Windows is preconfigured to see all UNIX folders as network drives, network is configured so you can immediately go on-line with Internet Explorer 3.0 or access SMB file shares. Mouse emulation works the same way as with modern virtualization software so you can seamlessly move the cursor between Windows 95 and IRIX windows. It also changes the Windows 95 screen resolution immediately after resizing the emulator window.

On the other side, games are not playable on my 400-MHz MIPS R12000. There are strange lags every few seconds (although between them, fps is similar to early Pentium systems). Office software runs ok and the only major limitation is in supporting up to 8-bit display modes (no more than 256 colors).

ATI Graphics Solution rev 3 and monochrome ADI DM-14 (1985-6)

My Vienna 286 (1987) has finally got a monochrome MDA monitor so I can put back the original graphics card (ATI Graphic Solution rev 3). This first ATI chip (CW16800-A) has functions necessary to drive CGA and MDA/Hercules modes, so you can connect both types of monitors although the card is very small. In fact, I was thinking that it was something much newer than the rest of the system but that was not true. ATI implemented most of the circuits in a big GAL (Gate Array Logic, maybe that’s why they were called Array Technologies, Inc.) which allowed them to make the card very compact.

I’ve started with MCGA graphics in 1989 and then with SVGA graphics in 1990. I had never had an opportunity to play with Hercules graphics modes, so I was extremely curious. Using high-resolution text-mode applications in an MDA mode (IBM Monochrome Display Adapter) is a pleasure on this long-persistence screen. Especially when you consider that the same experience was possible since day one with IBM 5150 PC in 1981.

Hercules Graphics Adapter (HGC) used almost the same signal timing as MDA and added a graphics mode where each pixel (720×348) could be changed independently. This allowed business applications to use high-resolution monochrome graphics (black/white) and the card became quite popular (ATI was not the only company making HGC clones).

HGC mode is not the best choice for gaming. Although a lot of games supported the HGC mode, they usually used a simple hack with CGA data. These were the typical approaches:

  • Prince of Persia: 320×200 CGA graphics is horizontally stretched to 640 pixels where each two adjacent pixels are used for dithering (4 shades -> 2 shades). There is no vertical expansion used in the game. The developers just put the 200-row graphics in the center of the 348-row screen.
  • Stunts improved the approach used in Prince of Persia. There is always a black row after two standard rows, so the screen is expanded to 300 rows. I’m surprised that it doesn’t look bad at all on the real CRT.
  • F-15 Strike Eagle tries to expand the graphics to the whole screen area. The vertical expansion is done by doubling every second row.
  • Microsoft Flight Simulator 3.0 looks great because it works with vector graphics. Thus, it can use the full HGC resolution. The result is better than with CGA with exception of the 16-color composite CGA output.

Fixing issues on an SGI keyboard

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There will be an annual vintage computer show called Bytefest soon in Prague, so my friend and I must prepare all the hardware we want to take with us. Last year, I was told by some visitors that it is inappropriate to use an IBM keyboard with SGI computers. Thus, we started our repairing marathon with this defective SGI keyboard (although I don’t think that using IBM Model M with any computer is inappropriate).

I’m used to the fact that servicing SGI computers is always pain in the ass. It seems that SGI peripherals are exactly the same story. The keyboard is designed the way that it is not possible to clean switches if you don’t want to disassemble the whole thing destructively.