OK, OK, not everyone reads service manuals and schematics for their keyboard. However, I do get a little frustrated when posters compare apples to oranges, and make statements like “I can buy 1GByte for $1 (USD), so why is Yamaha so stingy with wave memory?”

Here is some information from the S750/S950 and Tyros5 service manuals and product data sheets. Please keep in mind that there are many different kinds of memory in an arranger. I’m going to focus on tone generation because that is the most relevant to wave memory size.

Both the S750/S950 and Tyros5 use proprietary Yamaha tone generator integrated circuits designated “SWP51L”. The S750/S950 designs use one SWP51L and the Tyros5 has two SWP51L chips. Each SWP51L has two dedicated memory ports (called “HIGH” and “LOW”) where each port consists of an address bus and a 16-bit parallel data bus.

In the S750/S950, each port is connected to a WAVE ROM:

    S750 WAVE ROM-L 1Gbit IC308   JS28F00AM29EWLA
    S750 WAVE ROM-H 1Gbit IC302   JS28F00AM29EWLA

That’s 128MBytes per device for a total of 256MBytes (2 times 128MBytes).

The Tyros5 microarchitecture is a little more complicated — the memory devices are shared between two SWP51Ls via separate shared address and data busses. There are six WAVE ROM integrated circuits:

    Tyros5 WAVE ROM-L0 1Gbit IC702   S29GL01GS10TFI020
    Tyros5 WAVE ROM-H0 1Gbit IC716   S29GL01GS10TFI020
    Tyros5 WAVE ROM-L1 1Gbit IC703   S29GL01GS10TFI020
    Tyros5 WAVE ROM-H1 1Gbit IC717   S29GL01GS10TFI020
    Tyros5 WAVE ROM-L2 1Gbit IC704   S29GL01GS10TFI020
    Tyros5 WAVE ROM-H2 1Gbit IC718   S29GL01GS10TFI020

That’s a total of 768MBytes (6 times 128MBytes).

Those cryptic names in the tables above identify the specific memory component. The components come from two vendors: Micro Technology and Spansion. Here are the gory details.

    Micron Technology JS28F00AM29EWLA  56-pin TSOP
        Parallel NOR Flash Embedded Memory
        Configurable width data bus (8- or 16-bits)
        Asynchronous random/page read
            Page access speed: 25ns
            Random access speed: 110ns
            Page size: 16 words or 32 bytes

    Spansion S29GL01GS10TFI020 56-bit TSOP

        GL-S MirrorBit Eclipse Flash Non-Volatile Memory
        S29GL01GS 1 Gbit (128 Mbyte)
        16-bit parallel data bus
        Asynchronous 32-byte page read
            Page access speed: 25ns
            Random access speed: 100ns
        Program and erase rates (i.e., write speed)
            Buffer Programming (512 bytes) 1.5 MB/s
            Sector Erase (128 kbytes) 477 kB/s

The read speed (25ns per 16-bit word in page mode) is much faster than write speed, and that’s OK in this application because the data is always read once it’s loaded/initialized. The SWP51L probably operates in page mode since the samples are accessed sequentially. Dunno ’bout you, but 25 nanoseconds per 16-bit word is darned fast. The access speed is MUCH higher than a typical USB flash drive.

Two 27-bit address busses and two 16-bit data busses are sent to/from the plug-in expansion board. These busses extend the two shared WAVE ROM busses. The expansion board needs to keep up with the high read rate.

Please note that the CPU does not get anywhere near the sample streams. That work is assigned to the SWP51Ls.

Hope this helps to clarify.