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Technical information on computer specs for Hauptwerk
Part 2: memory
The amount of memory your computer has primarily determines the maximum size of sample set that can be loaded in Hauptwerk.
In order to achieve the very high polyhony necessary to model organs effectively, Hauptwerk needs to keep all of the samples in memory. Hard-drives are very slow compared to memory, and many, many drives would be required in parallel to achieve an equivalent polyphony by streaming samples from the hard-disk. Thus it usually works out considerably cheaper in terms of computer hardware to keep the samples in memory, particularly because computer memory is very cheap now.
Since Hauptwerk keeps all samples in memory, you must have sufficient physical memory free to load the largest sample set you intend to use entirely into memory. If you do not have enough memory, you will either get an 'out of memory' error when loading the sample set or some of the samples will be 'paged' temporarily to disk by the operating system, in which case it will not be possible to access them quickly enough when they are required, causing very unpleasant glitches in the the audio output.
The amount of free memory required for a given sample set is usually stated as a prerequisite by the creator of the sample set. We also try to give a basic guide figure for each Hauptwerk version 3 or version 2 sample set in our list of third-party sample sets. Roughly speaking, it depends upon:
- The number of samples.
- The average length of the samples. Dry samples usually require less memory because the release samples are shorter.
- The channel format of the samples - stereo or mono. Stereo requires twice as much memory as mono.
- The sample rate - 44.1, 48 or 96 kHz. Higher rates require more memory.
- The sample resolution - 16, 24 or 32-bit.
- Whether the sample set has multiple samples per pipe.
When you load a sample set in Hauptwerk you can choose not to load some of the ranks of pipes, so that you can fit a subset of a sample set into the memory available.
You can also choose to load 24 and 32-bit samples in 16-bit (the default) or 20-bit, very significantly reducing the memory requirement for 24-bit samples. The audible quality loss will be small since Hauptwerk performs all mixing and signal processing in 32-bit and produces output in the highest resolution supported by the audio/sound card, so the effective resolution is usually much higher than 16-bit even if the samples are loaded in 16-bit.
Various further per-rank memory saving options are available, such as loading only the first loop in a sample, loading a stereo sample in mono, loading at most one sample per pipe, or truncating its release samples, although they come at the expense of some realism.
The following is a very, very rough guide to the types of sample sets that might typically be usable in full within a given amount of memory:
- 1 GB: dry, mono organs <50 ranks; dry, stereo organs <30 ranks; wet, stereo organs <20 ranks.
- 2 GB: dry, mono organs <120 ranks; dry, stereo organs <60 ranks; wet, stereo organs <40 ranks.
- 3 GB: almost all dry organs; wet, stereo organs <50 ranks.
- 4 or 8 GB: very large and/or very wet, stereo organs and almost all dry organs.
However, please look at the requirements given by the sample set creators for the specific sample sets that are of interest to you. The St. Anne's, Moseley organ sample set included with Hauptwerk requires at least 1 GB of installed memory to be loaded fully, but its Great division alone can can be used on a computer with only 512 MB of memory.
The maximum amount of memory that can be installed in a computer is determined by its hardware (motherboard) and the operating system. Older computer hardware are commonly limited to 2 GB.
On the Apple Mac platform, Hauptwerk is fully supported on OS X 10.5 'Leopard' (versions 10.5.4 and above) and 10.4 'Tiger' (versions 10.4.11 and above). In general, we recommend Leopard over Tiger, since it has significant performance and stability improvements internally that are relevant to Hauptwerk.
The only notable disadvantage of Leopard is that it does not allow an application (such as Hauptwerk) to fill the memory as nearly as was possible with Tiger when 4 GB or less of physical memory is installed, so Hauptwerk might not be able to use quite as much memory on computers with 4 GB or less. Leopard typically allows Hauptwerk to use a maximum of about 62 percent of the physical memory before audio glitches become a risk (due to 'swapping').
A native 64-bit version of Hauptwerk is not yet available for Mac OS X (1), but OS X does allow Hauptwerk to access more memory than 32-bit Windows, so the absence of a native 64-bit version is less of a limitation on the Mac platform.
32-bit versions of Windows Vista and XP are limited to 2 GB or 2.7 GB, but a Windows configuration setting must be changed to enable support for the third GB.
64-bit PCs running 64-bit Windows Vista or Windows XP Professional x64 Edition (64-bit) can theoretically access many GBs of memory, subject to the limit for the motherboard. A 64-bit computer and 64-bit Windows Vista are thus recommended when buying a new PC system, provided that good drivers exist for the sound/audio and MIDI interfaces you intend to use. However, note that some audio and MIDI interfaces are not fully compatible with 64-bit Windows, and some only work properly with 32-bit software, so the memory limit is sometimes effectively 4 GB.
The clock rate of the memory makes a significant difference to the performance of Hauptwerk. Use the fastest memory that your system supports reliably. For example, if your motherboard can support PC2100, PC2700 and PC3200, use PC3200 memory throughout. In general on PCs, we recommend using ECC memory if your motherboard supports it, since ECC memory should lead to improved system stability. All computer memory will have occasioanl data errors which can lead to crashes or other unexpected results. ECC memory attempts to detect and correct such errors automatically.
For 64-bit systems that support dual-channel memory, ensure that both memory channels have separate but matching memory boards, which will also give a big performance improvement. For example, if you have a single 64-bit processor that supports dual-channel memory, and you require 2 GB of memory in total, install two 1 GB memory boards - one into a slot for each memory channel, rather than a single 2 GB board. All available memory channels and processors should be loaded equally for best performance (Hauptwerk is optimised for NUMA, and can take advantage of such memory configurations), and memory boards should be matched for maximum reliability.
When buying a computer it is also a good idea to consider allowing room for expanding the memory at a later date, i.e. buying a system with more memory slots than you need initially.
(1) Please see the enhancements page for more information about the status of the 64-bit Hauptwerk port for OS X.
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