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1750 RAM Expansion Unit - Gioco MAME

36939
c64_1750reu
1750 RAM Expansion Unit
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Dati principali
Romset e nome:
c64_1750reu 1750 RAM Expansion Unit
Nome semplificato:
1750 RAM Expansion Unit
Produttore:
-
Anno:
-
Genere:
Sistema
Categoria:
Sistema / Device
Serie:
-
Sorgente driver:
src/devices/bus/c64/reu.cpp
Lingua:
-
Giochi simili:
Input / Controlli
Giocatori:
Non gestiti
Controlli:
Non disponibile
Pulsanti / tasti:
0
Coins:
0
Cabinet:
-
Free-play:
Non supportato
Classifiche
Voto medio:
AntoPISA BestGame:
-
MASH All-Time:
-
Video
Schermo:
Non gestito
Orientamento:
Scorrimento:
Non indicato
Colori:
-
CPU:
MOS 8726 DMA Controller
Audio
Canali:
-
Chips audio:
Romset
Prima release:
Mess 0.150 del 17-set-2013
Ultima release:
Mame 0.226 del 28-ott-2020
Clone di:
-
Bios:
Non richiesto
Usa rom di:
-
Sample:
-
Rom set vecchio:
Nessuno
Rom set nuovo:
Nessuno
Files
Dump:
-
File richiesti:
-
Romset:
-
Stato emulazione
Complessivo:
BUONO
Emulazione:
Buono
Grafica:
Buono
Colore:
Buono
Suono:
Buono
Cocktail:
Buono
Protezione:
Buono
Salvataggio:
Non supportato
Dati aggiuntivi
  • History
  • Info
  • Score
  • PCB
  • Comandi
  • Init
  • Driver
  • XML
  • Informazioni fornite da © Alexis Bousiges
    NOTA: Non sono disponibili contenuti in italiano
    Other published 34 years ago:

    1700 / 1750 / 1764 REU © 1985 Commodore.

    Commodore's RAM Expansion Unit (REU) range of external RAM add-ons for their Commodore 64/128 home computers was announced at the same time as the C128. The REUs came in three models, initially the 1700 (128 KB) and 1750 (512 kB), and later the 1764 (256 kB, for the C64).

    TECHNICAL
    Although the C128 could access more than 64 kB of RAM through bank switching, the memory inside the REU could only be accessed by memory-transfers (STORE/LOAD/SWAP/COMPAREs) between the main memory and the REU memory, thus, giving an equivalent to a (slow) small memory window. Additionally, the C128's built-in BASIC 7.0 had three statements, STASH,FETCH, and SWAP, for storing and retrieving data from the REU.

    Officially, only the 1700 and 1750 were supported on the C128. The 256 kB model, the 1764, was released for the C64 at the same time. However, aside from a bundled 2.5 ampere C64 power supply unit (the factory unit could not support the 1764), there were only minor differences between the three models.

    In practice, the difference between the 1764 and the earlier units had little effect on compatibility, and people used 1700s and 1750s successfully with the C64, and 1764s successfully with the C128, although the C64's stock power supply was inadequate to reliably handle the power load of any of them. Some dealers unbundled the 1764 and the power supply in order to sell the power supply to C64 users, and/or upgrade the 1764 to 512 kB.

    The 1700s circuit board was identical to that of the 1750, and a trace marked J1 indicated the size of the chips used. On the 1750 and 1764, this trace was cut.

    The 1700 and 1750 had a resistor at position R4 that, according to Commodore engineer Fred Bowen, compensated for subtle differences in the expansion port on the C64 and C128. The 1764 lacked that resistor. Bowen and other CBM engineers recommended against using a 1764 with a C128 unless the resistor was added, or a 1700/1750 with a C64 unless the resistor was removed.

    It was possible to check for the presence of a 1750 by reading memory address $DF00's bit 4, which was 1 on a 1750, and 0 on a 1700 or 1764. However, since this procedure would not distinguish between a 1700 and a 1764, many programmers wrote to the RAM itself to find out the amount of memory installed.

    TRIVIA
    The need for the REU came about when Commodore management decided to not use the final version of the custom Memory Management Unit(MMU)which then limited the size of memory in spite of early discussion of a larger memory map. Engineers traveling to the 1985 CES show were confronted with flyers and billboards advertising a memory size that was no longer supported and finally the most upper management finally asked where the additional memory (Up to 512K) would plug in.

    By the time of the 1985 CES show in Chicago, the engineers were able to display a spinning globe of the earth as a demonstration of Direct Memory Access (DMA) memory access of the new REU units.

    Because of memory chip shortages in the late 1980s, the 1750 was only produced in small quantities. However it was not difficult to upgrade a 1700 or 1764 to 512 kB. Several firms did this commercially, either selling upgraded units or upgrading customer-supplied units.

    Very little software made use of the REUs. Like other add-on products from Commodore, their relatively small installed base relative to the huge installed base of the C64 made software developers hesitant to invest much time and effort in supporting it, and the lack of commercial support kept sales lower than they otherwise might have been.

    The REUs came with software to utilize the extra memory as a RAM disk, but the RAM disk's compatibility with commercial software was spotty, as some commercial software relied heavily on various quirks of the Commodore 1541 floppy drive. Additionally, many commercial programs simply overwrote the memory space occupied by the RAM disk software.

    The GEOS operating system had built in support for the REU as a RAM disk, as did the C128's version of CP/M, and some disk copy programs used the REU to facilitate high-speed copying with a single disk drive. GEOS as well as other programs even used the REU for quick memory transfers within the host machine's main memory by storing a memory block into the REU and then fetching it back to another location. Using this method, only the actual data to be transferred needed to travel on the machine's data bus—unlike the ordinary method, which had the computer's CPU do the transfer, thus spending at least three quarters of the bus capacity on instruction fetches and only one quarter or less on payload data.

    Due to its high speed relative to Commodore's floppy drives or even the commercially available hard drives, the REU also became popular with BBS operators.

    STAFF
    REU hardware designed by: Frank Palia
    Dedicated Integrated Circuit (IC) designed by: Victor Andrade
    Kernel & Basic: Fred Bowen, Terry Ryan
    Globe spinning demo: Hedley Davis

    CONTRIBUTE
    Edit this entry: https://www.arcade-history.com/?&page=detail&id=82049&o=2
    Informazioni fornite da Contribuisci alla traduzione da
  • Informazioni fornite da
    Informazioni fornite da / © Copyright by Fujix
  • Informazioni fornite da
  • Informazioni fornite da
  • Informazioni fornite da Fabricio Coroquer, tratto dal lavoro di
  • Informazioni fornite da Contruibisci da
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Dati aggiornati al 28 ottobre 2020


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c64_1750reu
Titolo:
1750 RAM Expansion Unit
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