Playing with TIGA #2 – repair

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Our SPEA Graphiti HiLite 1024 2D graphics accelerator finally works. The repair was faster than expected – it took less than an hour. We just fixed the broken traces between the GPU and RAMDAC and that was it. The card outputs very sharp workstation-quality image even in 1152×870 and 256 colors. We are one step further to start programing it.

Acorn A3020 with a PC HW Emulator

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It was common for many computer platforms to have a complete IBM PC compatible on a card in the 80s and early 90s. Software PC emulators were also a choice but their performance was usually very low. Having a card with a x86 CPU could solve the issue.

Acorn PC Card equipped with Cyrix 486SLC (25MHz) is almost as fast as Intel 486SX for certain tasks (main difference is in cache size: 1kB instead of 8kB) and the card allows you to get all the CPU performance. However if you expect full PC replacement, you would be very disappointed. The main limitation is in graphics performance. The card is usable only with text-mode programs and static graphics. Although VGA modes are emulated, even simple CGA games (like Alley Cat) are unplayable due to slow screen refresh. Good to mention that refresh speeds are somehow worse when PC Card output is changed from full-screen to windowed display.

I believe that it was better and probably not more expensive to buy a cheap PC clone instead of this card.

Mobile CPU Upgrades

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Siemens-Nixdorf PCD-4ND is a 486-based laptop from 1993-1995. It was quite popular in Germany and you could have seen a few of them still in use even ten years ago (mostly connected to expensive industrial devices using a serial port).

I like how easy it was to upgrade the CPU in this particular laptop. It took about 20 seconds to remove a small plastic cover and replace the CPU board. There were probably four options during the lifecycle of the machine – 25-MHz 486SX, 50-MHz 486DX2 and 75-MHz/100-MHz 486DX4 (Intel called it ‘Intel DX4’).

Note the WDC graphics chip below the CPU board slot. It shared the bus with the CPU as it was connected using VLB (= VESA Local Bus) instead of the older ISA/AT bus. This allowed to use fast 32-bit transfers on a frequency equal to the CPU external clock (25/33-MHz) without a sophisticated bus controller (EISA, PCI). This chip was used in many laptops of this era and it was surprisingly powerful. It allowed up to 1024×768 with 256 colors and 640×480 with 65k colors and it could accelerate bit-block transfers as well as graphics primitives.