an article about z80 affecting MSX computers was published

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By Manuel

Ascended (15680)

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22-12-2018, 09:55

Search for LPE-Z380, released around 2000 or so.

By erpirao

Paladin (929)

erpirao's picture

22-12-2018, 10:49

Manuel wrote:

Search for LPE-Z380, released around 2000 or so.

z380 Padial homepage

Z380 Architecture

By litwr

Rookie (30)

litwr's picture

23-12-2018, 09:06

Thanks! Smile

zett wrote:

if you want to make a future msx you best gona work on the stuff of lpe z380

IMHO if you need the best z80 it is somehow better to make it. Modern tools allow to do things much more efficient than in the 70s or 80s. So to make the proper FPGA design is rather not too difficult. Indeed to release an ASIC will require some funding but having the FPGA design may help here. IMHO super-z80 should have 2 ALU like Pentium.

By litwr

Rookie (30)

litwr's picture

28-12-2018, 10:55

I have had thoughts about the R800 and they raised a question. If the internal frequency of the R800 in the MSX TurboR is 28 MHz and the bus frequency is 7 MHz than it is a necessity to have a built-in cache. Is there any information about that cache size?

By lintweaker

Master (152)

lintweaker's picture

28-12-2018, 14:05

Not sure if cache is needed for a split CPU and bus frequency. The Z280 has 16k cache but that can also be disabled or used as RAM. The Z180 also has split CPU and bus frequencies but does not have cache.

corrected 32k cache -> 16k cache for Z280

By Grauw

Ascended (8366)

Grauw's picture

28-12-2018, 14:02

Afaik Z800 / Z280 has a cache of 16 blocks of 16 bytes, not 32K. Can also be set to a mode where it just acts as 256 bytes of fast memory.

The common knowledge is that the R800 relies on the CAS / RAS burst memory access trick to fetch sequential instructions quickly. Omitting a cache saves cost I guess. But maybe the common knowledge is incomplete, who knows Smile.

By lintweaker

Master (152)

lintweaker's picture

28-12-2018, 14:08

Corrected my 32k cache for Z280 to 16k (thx @Grauw).
Z280 has bugs with cache when in Z80 8-bit bus mode. Advice is to disable it when using Z80 bus mode. A real shame. Also the cache mechanism cannot handle self modifying code.

By Grauw

Ascended (8366)

Grauw's picture

28-12-2018, 14:11

Not 16K, 256 bytes (16x16).

By lintweaker

Master (152)

lintweaker's picture

28-12-2018, 14:34

Ai yes, only 256 bytes ... me with my 16/32k ....way to modern...:-)

By litwr

Rookie (30)

litwr's picture

29-12-2018, 15:03

Grauw wrote:

Afaik Z800 / Z280 has a cache of 16 blocks of 16 bytes, not 32K. Can also be set to a mode where it just acts as 256 bytes of fast memory.

Thanks for the information which means that the R800 can use a larger cache. It looks quite possible that the R800 uses more cache instead of the Z800's abandoned logic.
Have anybody tried to use the R800 cache as a fast memory? Does it work?

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