The return of the Acer 3000

by hobbitalastair

The Acer 3000 is back!

Last time I had issues with the power supply unit, which scuttled most experiments. I have since repaired it, following (vaguely) this article, which included links to information on repairing the power supply connector. That done, I decided to test it…

The results were good, initially. A battery life greater than one hour, no major flakiness (although it does seem to power off after an hour and a bit), and a smooth install.

At least, it all worked until I tried to start a desktop.

As it turns out, the SiS chip – a M760GX – does not work properly under Linux. Or at all. Here is an extract from this page on SiS chips and Linux:

3. A few words about the SiS 760 (all versions)
The SiS760 is a chipset for the AMD64 and AMD Sempron platform. These CPUs have a memory controller built-in, ie in systems based on these CPUs, there is no dedicated memory controller present.

As with all integrated SiS chipsets, the SiS 760 supports shared video memory, ie. memory that is shared between the system and the graphics (this technique is called “UMA”). However, the 76x also supports dedicated video RAM (so-called “local framebuffer memory” = “LFB”) which connects directly to the graphics chip and is accessible for the CPU via the bus. Shared memory and local memory can be combined (“hybrid mode”).

Shared memory is slower, because the graphics chip has to access it via the system memory bus, while it can access local framebuffer RAM directly. Most if not all modern graphics cards therefore use local video memory.

While shared memory was quite usable on all previous integrated chips (630/730, 65x, 661, 74x), there is a serious problem with it on the SiS760 – caused by the aforementioned fact that the CPU contains the system memory controller. This leads to severe memory bandwidth limitations if only shared system memory is used and no local framebuffer memory is present.

Therefore, the 760 – if used with shared memory only – is not really usable in dual head configurations; even in single-head operation, some features are limited. This especially affects video overlay support (Xv): Although the SiS760 supports two video overlays, these are in most cases not usable: Heavy flicker in the video and the graphics may occure as a result of exceeding the available memory bandwidth. The X driver takes some counter-measures on such systems (even advanced ones in the Premium Version), but it can’t avoid the problems entirely. On systems with both shared and local video memory, the drivers will only use the local memory part. You may likewise disable the shared memory in the BIOS.

My advice: Don’t buy a machine with a SiS760 unless this machine has dedicated local video memory. And please don’t complain about “driver bugs” if you see “flashing lines” on the screen; these are the typical effects of a bandwidth problem and unavoidable – even the Windows driver can’t do better. In such cases, reduce the resolution and/or refresh rate and/or color depth, or use one output (CRT1 or CRT2) only. Sorry, can’t help it. There is no driver bug involved.

For poor Averatec 6240 users: My drivers at least allow 1280×800 on the LCD if the external monitor is enabled… the Windows driver kicks you back to 1024×768 in such a case.

Not good!

Coupled with the lack of a driver for this particular chip, this did preclude a working (composited) desktop.

X also refused to start unless run with root privileges. Strangely. Since it worked last time I tried…

So, despite having 1GB+ of RAM, and a powerful Sempron CPU, it’s not really usable by modern standards.

Still, at least I learnt how to repair a broken power supply connector 🙂

EDIT: I should also note my inability to get the wifi working. But I didn’t exactly try very hard…

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